(Posted April 2001) Biodiversity Series CONTENTS Introduction Why Biodiversity Matters Appreciating the Benefits of Plant Biodiversity Bibliography IN FOCUS Coral Reefs Forests Wetlands Northlands THE PROBLEM OF BIODIVERSITY Since the human species first became fully conscious of the natural world, nature has usually seemed unassailable, and abundant with plant and animal life, from mountains, to oceans, to continental prairies. Over the course of the 20th century, however, this view has changed. Man's power over nature, assisted by machines, has grown, and human population has increased exponentially. For centuries, nature has been in retreat in the face of human settlement, but in the last 50 years, destruction of the natural world has picked up speed. Scientists believe that when human development and agriculture reduce the natural world, the loss is not simply a matter of size. The remaining natural areas, it is believed, harbor fewer species and complex ecosystems. Scientists who study "biodiversity" posit that many wild species are becoming extinct, and that this extinction of wild species -- many of them still unknown or not well understood -bodes ill for the future of the planet. Since the dawn of agriculture, human survival has been based on the domestication for food purposes of wild plants. Yet, many plant species are being destroyed in the wild, before their food or medicinal value can be assessed. The continuation of wild or partially-wild varieties of plants such as corn is necessary to the future health of domesticated varieties. In addition, whole ecosystems, such as riverine estuaries, coral reefs, montane forests, and the creatures that live in them, are under stress due to human-caused pollution or over-development. Yet, these ecosystems, in all their marvelous complexity, cleanse water of pollutants, provide the air we breathe, and produce much of our food, making human existence possible. In effect, the the vast web of biological diversity, with its millions of species on this planet, is what has made human survival possible, and human life fulfilling. This electronic publication contains two essays by respected authorities in the field of biodiversity. Four short essays focus on specific ecosystems of concern. In "Why Biodiversity Matters," an excerpt taken from his book "Life in the Balance, Humanity and the Biodiversity Crisis," Niles Eldredge, curator at the American Museum of Natural History, explains how the invention of agriculture made it possible for the human race to increase its numbers exponentially and spread across the planet. "The sheer bulk of human numbers," he writes, "probably nearly doubling to over 10 billion [thousand million] by mid-21st century -- is wreaking havoc on Earth, on its species, ecosystems, soils, waters, and atmosphere." Eldredge foresees a coming "Sixth Extinction" of life forms on this planet, rivaling the previous five known prehistoric mass extinctions of life in prehistoric times. Eldredge adds: "Everything is linked?. The world truly is a complex system, and we are a part of it, still dependent on its renewable productivity, which we ourselves are beginning to stifle." "Appreciating the Benefits of Plant Biodiversity," by John Tuxill, published in 1999 by the Worldwatch Institute, deals with plant extinction. Tuxill's thesis is that the survival of wild varieties of plants, or plants that have been domesticated but vary genetically from small farm to small farm, is extremely important, as variety in the plant genome can provide a way of breeding disease-resistant varieties and enriching human agriculture. "Plant biodiversity, in particular," Tuxill says, "is arguably the single greatest resource that humankind has garnered from nature during our long cultural development." He adds that due to modern agricultural practices, "we are eroding the very ecological foundations of plant biodiversity and losing unique gene pools, species, and even entire communities of species forever." The essays in this collection make it clear that the future of the human endeavor is linked now, as in the past, with the natural world. Many observers now feel that one of the prime responsibilities of human community, for spiritual, aesthetic, and extremely pragmatic reasons, must be to take steps to preserve biological diversity for future generations, before the richness of life on this planet is diminished forever. WHY BIODIVERSITY MATTERS By Niles Eldredge From Chapter 5 of Life in the Balance: Humanity and the Biodiversity Crisis, by permission of Nevraumont Publishing Co. Copyright ? 1998 Niles Eldredge. The San people of the Kalahari have no trouble whatever understanding the value of biodiversity: Until fairly recently, the San had been living in small bands wholly within their local ecosystems. All their food, their clothing, their shelter, their medicines, their cosmetics, their playthings, their musical instruments, their hunting weapons, everything came from the productivity of their surroundings, the plants and animals on which they completely depended for a living. Why, then, is it so difficult for most of us in the industrialized nations -- urban dwellers but also rural farming folk -- to grasp the significance of biodiversity? The answer, I truly believe, is that we have simply forgotten what the San and all other hunter-gathering peoples still know. We have forgotten because of a profound and radical change in our relation to the natural world that came as a direct consequence of the invention of agriculture. We need to understand how people fit into the natural world -- both as hunter-gatherers and as agriculturally based industrialized societies before we can assess realistically what biodiversity means to human life. For the first time in the entire history of life, one species, our species, Homo sapiens, has stepped outside of the local ecosystem. Agriculture changes the entire relation between humans and everything else living in the vicinity. To plow a field, to cultivate a handful of crop species, means the destruction of the dozens of native plant species that would otherwise be there naturally. No one ever heard of a "weed" until we began dictating what limited number of plant types we wanted to be growing on a given plot of land. What is the difference between living off the natural fruits of the land and living off those we grow ourselves? The answer is simple: To live off our own cultivars, we must disassemble original ecosystems. There is very little native North American prairie left in the Midwest, and therein lies the gist of the dilemma. Most of us genuinely think we don't need prairie at all. We see prairie as simply underutilized terrain. We even tend to look at marshes like the Hackensack meadowlands and see instead Giants Stadium and the potential for still more entertainment and business complexes rather than a New Jersey tidal wetland full of cattails, migrating birds, and larval marine life vital to the restocking of the marine fisheries on which we still so heavily depend. The Botswanan cattle industry looks at the grasslands of the Kalahari -- and increasingly, the greener pastures of the Okavango Delta itself -- as underutilized rangeland. We have come by this outlook honestly: Having stepped outside local ecosystems so successfully, starting 10,000 years ago, we have come to think that we no longer need prairies, wetlands, or any other kind of natural habitat. Agriculture has been a stunningly successful ecological strategy. Though famine has stalked the enterprise from its inception (there really is no such thing as complete control over food supplies, or anything else for that matter), the best indicator of ecological success is growth in population numbers. Estimates vary, but it seems likely that there were no more than 5 million humans on the planet 10,000 years ago. We had recently completed our spread throughout the globe by then, but we were still organized into relatively small groups as hunter-gatherers, still utterly dependent on the productivity of the local ecosystems in which we all continued to live. The upper limit on human population numbers back then was set by the same rules that govern the numbers of all other species: Each population is limited by the environmental carrying capacity, the number of individuals that, on average, a local habitat can support, taking into account available food and nutrient resources, and other important factors, such as prevalence of predators and disease-causing microbes, and even more general factors, such as climate and rainfall. Each local population is fixed at some fluctuating number, usually 30 or 40 individuals maximum, as was usually the case with San and other hunter-gathering human beings. Thus, the total number of individuals of any species is the average size of its local populations multiplied by the number of those existing populations. Agriculture popped the lid off natural regulation of human population size. No longer limited by the inherent productivity of local ecosystems, human agricultural societies began to expand immediately. Agriculture enables a settled existence -- and as populations began to grow, as patterns of political control and the division of labor began to emerge, human life rather quickly took on a semblance basically familiar to those of us living in even the most advanced of modern societies. Nor is this, of course, a "bad" thing: All of the great accomplishments of human civilization spring from our forsaking the local ecosystem and adopting agriculture as perhaps the pinnacle of our culture-dominated mode of making a living in the world. If high culture is one signal of our success, so too, in the time-honored measure of ecological success, is our geometric increase in the number of individual living humans at any given moment. If there were perhaps as many as 5 million people alive 10,000 years ago, there are now nearly 6 billion [thousand million] of us. We are engaged in a perpetual race to feed ourselves, and every time we come up with a clever expansion of agricultural technology -- whether it be crop rotation and efficient plowing techniques a few centuries ago, or biotechnological manipulation of the genetics of crop plants today -- human population numbers expand right along, so that there are always people on the brink of starvation somewhere. The sheer bulk of human numbers -- this 6 billion and ever-expanding, probably nearly doubling to over 10 billion by mid-21st century -- is wreaking havoc on Earth, on its species, ecosystems, soils, waters, and atmosphere. We are the current cause of this great environmental crisis, this threat to the global system that looms even as we approach the Second Millennium. We have created the biodiversity crisis, the next great wave of mass extinction that promises to rival the five greatest extinctions of the geologic past -- The Sixth Extinction?. THE VALUES OF BIODIVERSITY Three themes crop up in everybody's lists of why diversity matters. We have already encountered all three in passing. They are (1) utilitarian values (such as medicine and agriculture); (2) ecosystem services (vital functions such as the continued production of atmospheric oxygen); and (3) moral, ethical, and aesthetic values. Just as most of us don't know how our telephones, TV sets and computers work, we really have only the vaguest idea of where our foods and medicines come from. Harder yet to understand is the significance for our very existence of species and ecosystems which seem to just sit there and provide no obvious product for us to eat, use as fuel, or stock our medicine chests. Vaguer still is the calm sense of joy and simple belonging most urbanites experience with a simple walk in a woodlot, through a meadow, or along a clean shoreline. Yet these three categories of the effects of the living world on human life are absolutely crucial to modern and future human life on planet Earth. UTILITARIAN VALUES OF BIODIVERSITY When asked how many species humans routinely utilize in their daily life, most people (including most professional biologists) say, at most, perhaps one or two hundred. The correct answer is at least 40,000: Globally, each day we depend on over 40,000 species of plants, animals, fungi, and microbes. I am counting here only those species that we are deliberately exploiting. Still others, such as the microbe Escherichia coli, which lives by the millions in our intestines and is absolutely vital for normal digestion, are, fortunately, simply there. Many of us think that food comes from the grocery store, and have little idea of its ultimate provenance. If some of us realize that spaghetti comes, not from trees but from wheat flour, we still tend to think that the Agricultural Revolution is long since complete, that we have already abstracted from nature all the plant and animal species that we are ever going to farm. We think that whatever improvements in crop yield and disease resistance -- two critically important factors in the ongoing race to feed the 250,000 extra mouths we are currently adding each day -- can come strictly from improved breeding techniques, and especially from the seeming magic wrought by the recently developed techniques of biotechnology. Nothing could be farther from the truth. Here, a direct analogy with the natural world is apt: Evolution works through natural selection, the process Darwin (and Alfred Russell Wallace) discovered. On average, the organisms that thrive best will survive and reproduce, passing to their offspring the very traits that allowed them to flourish. Breeders do the same thing, allowing only those sheep, say, that have the woolliest coats to reproduce in the hopes of producing future sheep with even thicker coats than their forerunners had. But selection alone -- whether natural or artificial -- will not do the trick. Another ingredient is required: the presence of genetic variation. You can only select from an assortment of different traits. Once you have gone as far as you can in selecting from the available range of genetic traits, the process, inevitably, comes to a halt. The reason why evolution did not stop billions of years ago is that spontaneous genetic changes -- mutations -- occur each generation, renewing and increasing genetic variation. Biotechnology allows us to inject genes directly into domesticated plants and animals. At first glance, it seems that we have co-opted nature, once again substituting a clever bit of technology over a chancier and slower natural process. But the genes we insert to produce, say, frost-resistant strawberries, have to come from somewhere. You can't just go to a molecular biology facility and ask them to invent a gene that will make strawberry plants hardier. No one has the faintest idea what that gene would be, what its precise instructional coding would be, or where it might be inserted into the chromosomes of the strawberry cells. Biotechnology works the old-fashioned way: One must first find a genetic feature that performs the desired function, before it can be extracted, manipulated, and inserted with the marvels of modern biotechnological technique into the stock where you would like to see that desired effect expressed. That means we must find genetic variation in the usual place: in nature, in wild versions of domesticated species, and in their nearest relatives. For many crop plants, there is an additional ace in the hole: The centuries, indeed the millennia, that farmers have been patiently tilling the land, sowing seeds, and harvesting crops that are bountiful one year, skimpy the next, have seen the emergence of countless landraces, local varieties of corn, wheat, tomatoes, etc. that seem to do best in a particular combination of local soil and climate. The history of agriculture has itself produced, through simple artificial selection, a vast storehouse of genetic variation. All that variation is under serious threat. As science reporter Paul Raeburn recounts in his book The Last Harvest (1995), destruction of ecosystems in the wild threatens to obliterate countless species that are close kin to vital agricultural crops. He tells of the combination of skill, persistence, and luck that has enabled botanists from the United States and Mexico to locate a previously unknown species of wild corn, Zea diploperennis. This rare and rather unprepossessing plant promises to enable agricultural geneticists to abstract its genes, which convey resistance to a wide assortment of corn diseases. The alarming coda to an otherwise encouraging story of the importance of natural genetic variation in wild species to our collective agricultural effort is that Zea diploperennis almost certainly would have become extinct within at most a few decades as its limited natural habitat in Mexico's Sierra de Monantlan was suffering precisely the same sort of conversion (for agricultural use!) that we are witnessing around the entire globe. How many other wild relatives of domesticated species have we already lost, and what will the effects of that loss be as we struggle to feed increasing billions of people over the next several decades? Raeburn notes that a similar fate is meeting thousands of landraces. We lose species in the wild as we convert land for agricultural and other uses. We are losing landraces for a different reason: The switch from small single-family farming to large-scale agribusiness, coupled with recent dramatic advances in biotechnology, means we have begun to plant only a few "super" varieties of crop plants, apparently for good reason, as the crop yields have risen, and the quality remains high all the way to the dining room table. There is a downside to all this success. Big agribusiness has seen huge increases in both fertilizers and pesticides, with their ongoing deleterious effects on soils, rivers, and adjoining ecosystems. The loss of hard-won genetic diversity of these landraces also poses a deep threat to continued agricultural success in the future. It just doesn't do to put all your genetic eggs in a single basket -- allowing varieties with all sorts of as yet-unexploited valuable features to disappear in the rush to concentrate on a few, genetically homogeneous strains. Genetic diversity is the key to past, present, and assuredly future agricultural success. It is the key, as well, to our utilization of virtually all natural products. The medicines in our pharmacopoeia are as compelling an example as the agriculture story. Although we might be aware, in a vague way, that aspirin was originally extracted from the bark of willow trees, and that Europeans first learned of the drug through contact with native Americans, few of us have any idea of the extent to which indigenous healing practices, and the most sophisticated research and development efforts of the world's biggest pharmaceutical companies, rely on the genetic diversity of wild species. Graphic examples of the importance of wild plants to the development of new drugs have recently become famous: The Madagascar periwinkle, a wildflower and close relative of a common decorative horticultural variety, has yielded a drug that has proven effective against two forms of childhood leukemia. Taxol, extracted from the bark of the Pacific yew, is now an important part of the chemical arsenal marshaled against ovarian cancer. We have already encountered the drug extracted from the seed pods of the sausage tree in the Okavango Delta and other African locales, a drug recently shown to be an effective agent against skin cancer. True, taxol and other potent drugs can be made synthetically in the laboratory. The point is, though, that we first have to know about the existence of these compounds before we can make them. It would be folly -- and horrendously expensive and time-consuming -to sit around a laboratory randomly cooking up compounds in the hope that one of them might prove useful to combat a particular disease. As you might expect, local peoples who are closely tied to the land, and have not forsaken the old hunter-gathering mode for agriculture, have a vast storehouse of knowledge about the natural world around them. Scientific explorers have been repeatedly struck by the detailed knowledge of local peoples concerning the plant and animal species in their environment. For example, a new species, the golden bamboo lemur (lemurs are primitive primate relatives of monkeys and apes), was discovered by Western-world primatologists living in a section of western rain forest in Madagascar in the 1980s. The local peoples had known of its existence and the fact that it was different from its close relative, the greater bamboo lemur, which the Western biologists had confused it with. They could tell just by listening to its nighttime cries coming from the forest that the golden lemur is a distinct thing -what we westerners call a distinct "species." More graphic still are the accounts from earlier expeditions. While collecting birds in the 1930s in New Guinea, the famous ornithologist Ernst Mayr found that the local tribesmen knew all the species that he could locate and actually could point to two confusingly similar species and tell him they were different. Nowadays, ethnobotany and ethnozoology are important areas of research -- not least for what they reveal of the utility of plant and animal species already well-known to indigenous people. Local expertise about native plants and animals has other implications, as well. When we compare lists of plants and animals drawn up by local peoples with those of professional biologists, it confirms our notion that species are real entities in the natural world, not just figments of Western-world classificatory imaginations. Local expertise can also dovetail conservation efforts with the economic needs of indigenous peoples: for example, by paying locals to act as guides in conservation reserves, or to serve as parataxonomists helping in the sorting and identification of species -- the "elemental particles" of biodiversity -- in biologically poorly known regions. The world holds far more than the 40,000 or so species currently being utilized on a daily basis. That is why the exploratory research efforts of the chemical and pharmaceutical industries must go beyond simply cataloguing the experiences of local peoples. Although we have no precise idea of how many plant, animal, fungal, and microbial species populate the planet, there are at least 10 million of them. The living world is a vast cauldron of genetic variation: Most of it remains entirely unknown to us, yet much is undoubtedly of great potential use. For good reason, much of the exploratory research has been focused on the tropical rain forests. Most of the terrestrial species of our planet reside in the Tropics, and tropical forests are disappearing at a frightening clip. Estimates vary, but 30 hectares per minute now seems, if anything, to be an underestimate. More recently, however, some attention has been shifted to the sea, the last great earthly frontier. We are, of course, ourselves a terrestrial species, having abandoned the sea to take up life on land some 350 million years ago. Until recently, our direct utilization of sea life has been restricted to fishing and to hunting marine mammals. This last great vestige of a hunting-gathering mode of existence until recently threatened to extirpate many whale and seal species and, as we have already seen, now threatens to collapse the most productive fisheries in the world. Corals and sponges are but two of the major groups of marine invertebrate animals that live firmly rooted to the sea floor. They don't move around, so they can't escape when a predatory fish or crab comes by and tries to bite off a piece. These sessile creatures have evolved a stunning array of chemical defenses against such attacks -defenses that have recently begun to attract a lot of attention from the chemical and pharmaceutical industries. The case for the great diversity of living species as a storehouse of vital genetic variation is crystal clear. We have relied upon that variation increasingly since we developed agriculture, even as it has indeed seemed that we were abandoning nature. That reliance on the natural genetic storehouse will only increase as time goes on, a compelling reason why we must arrest the destruction of ecosystems and species that right now is systematically dismantling and destroying this vital resource. Specific utilitarian uses are only part of the story. Ultimately what might prove even more crucial is the simple overall health of the global system: the purity of the air, the balance among carbon dioxide, oxygen, nitrogen, and other gases of the atmosphere; the quality and circulation of water; the vital cycles of carbon, nitrogen, phosphorous, and other atomic constituents of our bodies. In short, in fouling our nests, in destroying ecosystems, and driving many species to extinction, we are beginning to approach a limit on how much of the global living system -- and we ourselves -- can actually survive. In the long run, the most valuable aspect of diversity may well be the ability of our species to continue to live on the planet. EARTH'S ECOSYSTEM SERVICES Why, one might reasonably ask, need we worry about the health of local ecosystems if we ourselves in large measure no longer live within them? Why can't we continue our 10,000-year course of habitat conversion and ecosystem destruction now that most of us no longer look to local renewable resources in our daily lives? Can we not live in a world wholly of our own cultural devising -- without all but a few of the world's species, on which we realize we have come to depend? No, we cannot. We have emerged at the other end of the 10,000-year honeymoon with agriculture -- and the consequent explosion in our population numbers -- and have begun to see that we are part of the global system, after all. Earth comprises a global system of interacting elements: the atmosphere, the lithosphere (soils and rocks), the hydrosphere (oceans, lakes, streams), and the Biosphere -- all of life. That global system is the summation of all those local systems interlocked across the entire face of Earth. Earth is our home -- where we were born, where we live now, and (space-travel fantasies notwithstanding) where we will have to stay if we have any chance of long-term survival. What effect does the Biosphere have on us? What does the Biosphere do for us? Simple, essential, and downright fundamental things -- things that we mostly don't see, appreciate, or fully understand -- without which, life on Earth for all species, including ourselves, would be completely impossible. Take the air we breathe. The atmosphere close to Earth's surface is mostly inert nitrogen (79%), which in itself is a good thing, as an atmosphere richer in oxygen than it already is (20.9%) would literally fan the flames of out-of-control wildfires. When we talk about the air we breathe, most of us mean oxygen. Oxygen is absolutely essential to all but a very few forms of microbial life. Some bacterial species use alternative chemical pathways to break down the nutrients on which they live, but all the rest -- most microbes, plants, fungi, and animals, including human beings -- require a constant supply of oxygen just to exist. Where does atmospheric oxygen come from? With billions of organisms taking in oxygen, and expelling carbon dioxide, surely we would soon deplete this essential resource. The answer, of course, is photosynthesis, the process whereby some bacterial and other, more complex microbes, as well as all green plants, trap solar energy by producing sugars and releasing oxygen as an incidental by-product. Though no one seriously thinks that our supply of oxygen is in imminent danger of collapse, it is important to realize just where the daily replenishment of this most precious resource comes from. Most of the world's fresh supplies of oxygen are produced by single-celled, microscopic plantlike organisms floating near the surface of the oceans, supplemented, of course, by the photosynthesizing activities of terrestrial plants. The mighty oceans are the last great frontier of relatively undespoiled natural habitat, but land-based human activity is beginning to sicken even them. Pollutants reaching the sea through streams and via the atmosphere (as gases are dissolved in water droplets), direct oceanic dumping, and the degradation of natural marine ecosystems through overfishing and mining operations are beginning to have their cumulative effects. Consider what else green plants do for us. I was struck by a recent report detailing the salutary effects of a single, mature shade tree alongside a house in Chicago. Shade in the summer, insulation in the winter, and, amazingly, measurable purification of the air immediately surrounding the house. Once, while visiting the botanical gardens in Naples, Italy, a botanist told me that the air where we were standing was some six times purer than the air on the traffic-congested street only some 200 meters away from us! Green plants have the happy facility of filtering out noxious gases, utilizing carbon dioxide in the very act of photosynthesis, but also absorbing other noxious effluents and even particulate matter from dirty air. They give us life-sustaining oxygen and also act as filters -- quite a dramatic bargain. Plants do even more than enrich and cleanse the atmosphere. The Amazonian rain forest controls the water cycle in that region, as trees transpire a tremendous amount of water every day. In addition, tree roots hold soil in place, so that cutting forests always leads to massive amounts of erosion. Indeed, Earth is losing 25 billion tons of topsoil through erosion each year -- a direct reflection of our conversion of natural vegetation for agricultural use, and an ominous portent of the difficulties that lie ahead for our continued reliance on agriculture. Consider, for the moment, the net effect of increased erosion from denuded lands on the entire Biospheric system. Coral reefs which typically fringe the shorelines in tropical oceans are beginning to show worldwide distress. One factor in their decline is increased erosional runoff of silts from the cutting of tropical rain forests. For all their massive structure, corals are actually delicate colonial animals that are extremely sensitive to silt content in water. They quickly die when clear tropical waters become clouded with particles of clay and quartz, as has happened recently in Belize. Coral reefs themselves provide a protective barrier to other delicate ecosystems, such as the mangroves fringing the southern tip of Florida. As we have already seen, coastal wetlands are the breeding grounds of countless species of fish and shellfish. Without viable, functional coastal wetlands, our fisheries -- already on the verge of collapse in many places, overtaxed as they are by incessant and often ruinous fishing practices -- would soon be in even worse shape. Everything is linked. We are accustomed to hearing that a complex web of energy flow -- who eats whom -- links all creatures in a local ecosystem. This is equally true of the Biosphere itself: What happens in the Amazonian rain forest ultimately affects not only the conspicuous mammals and birds of that forest, but also its fishes; runoff from the river affects the oceans, and all of its life. Decline of the fishing productivity on the Georges Banks off the Newfoundland coast can be traced in part to the cutting of tropical rain forests, as breeding of migratory fishes is disrupted far from the point where they are eventually hauled in by fishermen. The world truly is a complex system, and we are a part of it, still dependent on its renewable productivity, which we ourselves are beginning to stifle. We have by no means exhausted the list of ecosystem services rendered by plants. Several absolutely essential elements -- nitrogen and phosphorous to name but two -- are derived from the plant world. Even though nitrogen is an essential element of all proteins, only a few forms of bacteria (aptly called nitrogen-fixing bacteria) can extract nitrogen from the atmosphere and incorporate it directly into their bodies. Some plants such as the legumes (peas and their relatives) harbor nitrogen-fixing bacteria amid their roots -- a form of farming, in a sense. All the nitrogen in our bodies comes from eating plants or other animals that have eaten plants. The cycle is complete when decay organisms decompose dead plants and animals, producing ammonia, which is then converted by other bacteria to nitrates that plants can pick back up directly from the soil and to free atmospheric nitrogen. There can be no doubt that the Biospheric system -- in particular, the vast range of organisms, from microbes to plants, fungi, and animals -- plays a far greater role in our everyday lives than we think. We take them for granted -- as we do our agriculturally produced foods, our cars, and our TV sets. That's fine -- so long as we don't tip the applecart, by destroying so many of the world's local ecosystems that we compromise the Biosphere's cycles and our very existence. A MORAL AND AESTHETIC IMPERATIVE Although we need the Biosphere's species for our own uses, and we rely on those species for the basic supplies of food, water, and chemical compounds on which all life depends, there is still a third category of concerns for the natural world -- a third set of reasons to cherish the natural world and to resist its wanton destruction. Harder to define with precision, the aesthetic appeal and moral challenge posed by Nature are to some the most compelling reasons to ward off the impending Sixth Extinction. Not all of the world's major religions adopt the basic premise of the Judeo-Christian tradition, that the world and its living creatures were placed there by the Creator for our own human use. Genesis specifically exhorts humans to seek dominion over the beasts of the field. Recently, however, some theologians of the Judeo-Christian tradition have come to see the biblical exhortation as a call to stewardship; that is, our role ought to be as caretakers rather than as masters, to safe-guard the richness of the natural world, rather than to plunder it. Just as the Genesis role strikes me as an accurate assessment of the newly established order after the advent of the Agricultural Revolution (and Genesis was written not long thereafter), this newer theological interpretation, in my view, dovetails very nicely with the present condition of humanity vis-a-vis the natural world. Other religious traditions, of course, espouse radically different views of nature and the place that humans take in the natural world. The oneness of humans with the rest of animate nature is perhaps especially apparent in the Hindu tradition, where the doctrine of reincarnation sees a continuity between humans and other species only matched in the Western world by the intellectual concept of organic evolution. Other traditions of the Far East -- Buddhism and Shintoism, for example -- also, in their different ways, locate humans as part of the natural firmament, and not especially exalted above the beasts of the field. These religions, it has been suggested, may make it easier for those raised in their tradition to see the urgent necessity of halting the blind, errant destruction of the natural world surrounding us all -- easier, that is, than it is proving to be for those raised in Euro-centered, Western-world traditions. Religion, of course, is not the sole source of moral suasion, and ethical concerns of what is right, and what we ought and ought not to do, have been arising on their own with increasing frequency as the early stages of the Sixth Extinction intensify. Cries for adopting a conservation ethic -- one thinks here as much of Theodore Roosevelt and other far-sighted people of his generation as of the more recent (yet before their time) American environmentalists Aldo Leopold and Rachel Carson -- are often tied to a sense of belonging to the natural world. A feeling, not just an intellectual grasp, of somehow still belonging to the natural world pervades the words of these early prophets -- as when Rachel Carson, in the very title of her most famous book, Silent Spring, asked us to consider what spring would be like without the songs of birds and the hum of insects. These are essentially aesthetic feelings -- the notion that human beings just cannot expect to live completely successfully and happily strictly in the steel, concrete, and plastic world that increasingly appears to lie in the future. Famed Harvard biologist and biodiversity spokesman E.0. Wilson speaks of biophilia, his term for what he considers to be an innate sense of belonging to the natural world that, though subdued, is still present in all of humanity. Though we have proven to be mighty adaptable, I have a feeling he is basically right. The old saying "You can take the boy out of the country, but you can't take the country out of the boy" has a powerful analogue that encompasses us all. You can take people out of nature (local ecosystems, at least), but you cannot take nature out of people. That may well be the best reason for us to confront the Sixth Extinction. SOME GLOBAL ISSUES "Study Finds Sperm Counts Are Declining." So reads a recent headline, not in the Inquirer, but in the New York Times. There is evidence -- convincing to some, although not all, medical researchers -- that the amount of sperm produced by human males in both Europe and North America has, on average, declined in the years since World War II. The story is dramatic, but the idea that someone could suggest such a far-flung effect on a biological function so fundamental to human existence is indicative of a much more general set of signals that the global system is hurting. Scientists, thankfully, are a conservative lot, and all recent claims of global phenomena -- including purely physical changes such as global warming, holes in the ozone layer, and increase in frequency and intensity of the El Nino climatic effect -have nearly as many doubters as proponents. It is always difficult to establish with absolute certainty that a recent trend -- say, increase in global temperatures -represents the predicted effect of increase in carbon dioxide and other gases in the atmosphere that have been accumulating since the advent of the Industrial Revolution. After all, we have direct recordings of global temperature for at best only the last century. More importantly, we also know that Earth has been sporadically, but on the whole steadily, warming up naturally for the past 12,000 years, when the last ice age ended and the huge sheets of continental glacial ice began to retreat toward the North Pole. It could be that the warming that has occurred during the twentieth century -- a rise in global average temperature of 0.5C causing a 2-centimeter rise in sea level along the Eastern seaboard of the United States -- is merely the continuation of a 12,000year-old natural trend. On the other hand, carbon dioxide helps trap solar energy, keeping reflected light from bouncing entirely back into the voids of space. The equations are there: The more carbon dioxide in the atmosphere, the more solar energy will be trapped, and the higher the world's average temperatures will become. The recent dramatic rise in global temperature may well be, at least in part, a side effect of human activity: The progressive rise in burning of fossil fuels over the past several centuries and the more recent, but no less devastating, burning of forests, primarily in the world's tropical belts. We may be uncertain and even skeptical, but we cannot afford to ignore the signs. The data are scant, so far, on the possible decline in human sperm counts, but there are several other apparent cases of negative global effects on life that seem almost certain to be caused by changes in the atmosphere -- changes wrought as a purely unintended result of human activity. One now well-studied example is the worldwide, and often rather precipitous, decline in frog and salamander populations over the last decade. I had noticed a sharp reduction in the half-dozen species of frogs and toads in and around my favorite little pond in the Adirondack Mountains of New York State. In the early 1970s, when I first started looking, there were green and bull frogs galore down in the pond, in populations so dense that the bulls were keeping us awake at night with their calls, and restaurateurs were shooting them for their bills of fare. American toads and wood and pickerel frogs were leaping all over the place along the pond's edge. Since the 1980s, it has been hard to see any of these species. But that is just one little spot, and for all I knew, I was just witnessing a natural fluctuation of population numbers -- though it did strike me as odd that all the frogs and salamanders in my one little spot seemed to be declining at the same time. My Adirondack amphibian experiences are decidedly anecdotal -- just casual impressions. Imagine my surprise when I learned that professional herpetologists had begun to notice an apparent worldwide decline in frog and salamander populations. More recently, frog populations all over the United States are producing many deformed individuals, a phenomenon first noted by Midwestern schoolchildren. Just as in the case of global warming, experts on frogs and salamanders are divided on this apparent pattern. Is the decline real? If so, is it somehow just normal fluctuation, or is the decline at least in part caused by human-engendered environmental change? If human environmental disruption is the culprit, is the reduction of frog and salamander populations more a matter of alteration of local habitats, or is there some truly global factor at work? All herpetologists seem to agree that there is an urgent need for serious, long term studies to get a firm handle on what precisely is happening to the world's frogs and salamanders. There is already enough evidence to convince some serious biologists that the amphibian decline is indeed real, and is affecting the great majority of the more than 5,000 frog and salamander species known to exist in the modern world. Severe alteration of local habitats lies at the very heart of extinction, and many frog populations seem to have been reduced through human conversion of their habitats for our own purposes. More subtle, but still in keeping with the theme of human interference on the local level, is the use of pesticides and the introduction of other toxicants. Back to the anecdotal, I do note that my observation of the frog and salamander decline in the Adirondacks in the 1980s coincided with a determined spraying program aimed at reducing the numbers of mosquitoes and black flies that attack humans and depress the flow of summer tourist dollars. Pesticides -- or the human-induced drop in edible insects -- may well underlie the reduction of amphibian numbers in many places. Yet the tantalizing possibility remains that the worldwide decline may actually represent a truly global cause. In other words, the global pattern is not just the summation of isolated local effects but is actually caused by some factor that itself acts on a global basis. Frog and salamanders must return to the water to reproduce, and the skins of many species are delicate and more permeable to various substances than is the typical case for reptiles, birds, and mammals. Many species of frogs and salamanders are known to be sensitive environmental indicators; frogs, for example, are often good indicators of rising acid content in their native waters, as their numbers typically decline as levels of acidity rise. What global factors could conceivably underlie the amphibian decline? Oregon State University herpetologist Andrew Blaustein -- a cautious student of the problem -- has suggested at least two possibilities. For one, there is a fungus known to attack, and to reduce the viability, of frog eggs. The fungus is found around the world, and perhaps a recent expansion of its range, or its potency, has contributed to the amphibian decline. More suggestive is the more recent hypothesis that an increase in the level of intensity of ultraviolet (UV) radiation is causing the decline. Blaustein and his colleagues have found that the developing eggs of frog species known to be declining are more sensitive to -- more damaged by -- exposure to a given level of UV radiation than are the eggs of frogs whose population numbers have remained relatively stable in recent years. Ultraviolet radiation. That rings a bell -- as anyone who has read of the recent alarming rise in incidence of human skin cancer well knows. The medical literature has established a firm link between exposure of human skin to the sun and the occurrence of skin cancer -- a correlation that, like that between lung cancer and smoking, implies actual cause and effect to most medical professionals. Dermatologists are in virtually unanimous agreement that exposure to UV radiation is one of the causes of skin cancer. Careful measurements by atmospheric physicists indicate that UV radiation has definitely been on the rise. The increase is especially apparent in the higher latitudes, closer to the North and South Poles than to the equator. Much of the UV component of solar radiation is absorbed by ozone, a molecule consisting of three atoms of oxygen. Each winter, the natural layer of ozone in the atmosphere thins, at places disappearing entirely. In recent decades, satellite imagery and balloon probes alike have revealed increasingly large and persistent rents -- holes -- in the ozone layer. Damage to Earth's protective ozone layer was actually predicted: Chlorofluorocarbons -- organic compounds widely and routinely used in aerosol cans after World War II -- were known to interact with ozone, destroying large quantities of it in a one-way chemical reaction. That, it is widely agreed, is precisely what has happened. Spray cans, in this roundabout yet deadly way, are responsible for the epidemic increase in human skin cancers and perhaps the decline of many amphibian populations as well. There are several critical lessons here. First, we see that humans are indeed capable of altering the global system -- in this instance, the atmosphere. We also see that such changes can have profound effects on living things -- in this particular example, most clearly and convincingly documented in the rise of skin cancer in humans. We also see that negative effects -- amphibian population declines -- occurring globally may result from a single global cause, or may be the simple, yet nonetheless devastating cumulative effect of local habitat disruption and destruction. There are other lessons as well. Though some biologists point to the economic importance to humans represented by frogs (by keeping insect pest populations at bay, for example), and though many of us feel the noisy booming of bull frogs is a welcome nighttime experience, many citizens of the modern world more than likely would maintain that the world (meaning, of course, the human world) could get along just fine without those 5,000-odd species of frogs and salamanders. They would be missing the main lesson here: The real significance of the global decline of frogs and salamanders is that the amphibians are telling us something about the state of the atmosphere and, thus, of the global system as a whole. Human skin and frogs eggs just happen to be at the higher end of sensitivity to UV radiation. Amphibians -- and human skin for that matter -- are global analogues of miner's canaries, early warning systems that all is not right with the global system. The emerging story of the increase of atmospheric UV radiation through human agency -- and its boomerang effects on us and quite likely all other living systems -is stark, dramatic, and fairly easy to comprehend. More subtle are the negative effects on human life of human-engendered destruction of natural ecosystems and the consequent loss of species. It has proven difficult to explain what the loss of the northern spotted owl of the old-growth forests of the Pacific Northwest really means to local people, especially those engaged in the lumber industry in Oregon and Washington, to those of us living elsewhere in the United States, and ultimately to the people of the world. It simply doesn't make much intuitive sense to claim that the loss of a few hundred pairs of owls -- which hardly anyone actually ever sees -will have a profound negative effect on human existence. Yet it does matter. Those owls are a litmus test of the health of the ecosystem in which they live, and we are now beginning to understand that we depend on those systems far more than we imagined since we invented agriculture and stepped away from the local ecosystem. THE SIXTH EXTINCTION Biologists do not know exactly how many species are currently on the planet. Science has recorded and named some 1.6 million species, but we know this can only be some small fraction -- no more than 10% to 15% -- of the true number. Some biologists believe we have identified only 1% to 3%, and that there may be as many as 100 million species on the planet. Because concern over the accelerating loss of species has been mounting, biologists have turned in earnest to the key question, How many species are on Earth? They have begun to converge on an estimate of some 14 million species, but opinions still sharply differ on this vital issue. Why are we so ignorant of the biotic riches of Earth? Scientific survey of the world's species began in the seventeenth century, but did not switch into high gear until the mid-nineteenth century, when the heyday of European colonialism mixed with the Industrial Revolution, producing a blossoming of exploration and scientific inquiry. Naturalists like Alfred Russell Wallace and Henry Walter Bates traveled to then-exotic destinations such as the Amazon Basin and the Spice Islands (part of present-day Indonesia) to amass vast collections of plants, insects, spiders, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. The collections of such intrepid explorers found their way at first into privately held "cabinets" of natural history and increasingly into the large natural history museums that were founded in the midnineteenth century -- museums such as the British Museum of Natural History in London, the Natural History Museum of the Smithsonian Institution in Washington, D.C., and my own favorite treasure trove, the American Museum of Natural History in New York. Natural history museums are libraries of biodiversity, storehouses of the world's biological riches, where scientists can compare specimens and assess the identities and evolutionary relationships of the world's species. Though research biologists at major universities have historically contributed to the effort of finding, describing, and naming the world's species, increasingly this role has concentrated in the hands of the scientific staff of major natural history museums. Systematics is the branch of biology devoted to describing Earth's species, analyzing their evolutionary relationships, and producing biological classifications. Because biology keeps expanding (most recently into the realm of biomolecules), and because vast collections of specimens are needed as part of the routine work of systematists, museums have become the focal point for systematics research. Needless to say, there are far more species than experts to identify them. For some groups, there are few (sometimes no) experts actively working to inventory the world's stock. One way biologists frame accurate guesstimates of how many species probably exist in the world is to assess what we know we have found already, observe the rate that new species are turning up, evaluate how concerted the effort is to find new species for a given group, and derive some sense of what might still be out there, as yet unidentified. Ornithologists think that they have found most of the world's bird species, as the number has begun to level off at around 9,000, and mammalogists also think they have described and named well over 90% of the world's mammal species. As we have seen, even large species of mammals still turn up on a regular basis, such as the large antelope and deer recently discovered in recently war-ravaged Vietnam and the several species of lemur discovered over the past decade on Madagascar. New bird species also turn up regularly. Because so many systematists have focused on birds and mammals -- big and obvious, the charismatic megafauna -- and because much more numerous groups, such as insects, have received relatively much less attention, the ratio of named to as-yet-undiscovered species varies widely from group to group. There is yet another major source of inference for assessing the actual number of species on Earth, one that is tied into the very critical question, How do we know that we are in the midst of a sixth, major global mass extinction? The connecting link is habitat, by now familiar as the essential ingredient in species loss, but one which, quite obviously, underlies the sheer existence of species. In an elegant series of studies, Smithsonian coelopterist Terry Erwin came to his bynow famous -- and still controversial -- estimate that there are some 30 million species of insects in the Tropics alone. Erwin carefully sampled the insect(especially beetle) faunas of various forest canopies in Panama, Brazil, and Amazonian Peru. Erwin's goal was to determine how limited beetle species were, on average, to particular types of trees. Then, taking into account the total aerial extent and canopy diversity of the tropical rain forest, he was able to derive an estimate of the total number of beetle species currently in existence, and from that estimate extrapolated an estimate for the total number of insects. Coming as it did when most of the world's biologists were still thinking that there are at most only a few million species on Earth, Erwin's analysis shocked a lot of biologists into attention. More recent work, including similar in-depth, total assaying of a region's biotic riches, have tempered his estimates somewhat, but we now are accustomed to thinking that there are at least 10 million species of insects, rather than 1 to 2 million species, a 10-fold increase in our estimates of Earth's living species diversity. If so rich a percentage of the world's species is yet undiscovered, then their loss, their undocumented extinction, becomes more critical. Loss of unstudied genetic diversity means never to have that knowledge and never to be able to utilize whatever potential those species might have had, one of the major reasons humanity has become alarmed at the growing rate of destruction of the world's species. How do we measure that rate of disappearance? One simple and obvious way is to record the number of species -- such as the passenger pigeon, the dodo, and the great auk -- that are known to have become extinct in historic times. A related approach is to evaluate how well species that have been placed on threatened and endangered lists have fared. Appendix I [of the book] shows the documented species extinctions since 1600. Although they are considerable, they seem hardly the stuff of catastrophic mass extinction. Is the current loss of biodiversity overestimated? Are we really in the throes of a major mass extinction, the Sixth Extinction? Other approaches to measuring extinction rates yield more alarming results. Many species in museum collections simply can no longer be found in the wild. Many of my colleagues at the American Museum of Natural History have told me of returning to locales where, a few years earlier, they had found new species -- in one case, a new species of spider in Chile -- only to discover that the species' habitat had disappeared. Thus, we can use the very same sort of reasoning that gives us one way of estimating the number of species that exist (complete sampling of species richness in finite areas) to yield an estimate of the rate of species loss. We can measure the rate of habitat destruction. Aerial and satellite photography have revealed that tropical rain forests are being destroyed at a rate of some 12 million hectares a year. Combining known rates of habitat destruction with accurate assessment of numbers of species occurring per hectare in tropical rain forests, and the average size of areas they occupy, yields rough but credible estimates of current rates of species loss. We have already encountered the most famous of these: E.0. Wilson's figure of 27,000 species a year, which boils down to 3 species an hour lost forever. Some biologists think Wilson's figure is too high, but plenty more think he has underestimated the situation. How can we reconcile the rather low rates of extinction revealed from actual documented examples with the vastly more impressive -- and troubling -- estimates based on loss of habitat acreage? Most of the documented examples of extinction in the past few hundred years involve large, easily observed species (such as the quagga, a zebralike horse species); species from islands, where diversity is most easily monitored (the dodo was a giant, flightless pigeon living on the island of Mauritius in the Indian Ocean); and the well-studied north temperate latitudes, where the vast majority of the world's biologists have lived and worked (the passenger pigeon was a North American species). We know about these species simply because we have had the opportunity to study them and observe their loss. There is more to the story than simple convenience of study. The Tropics harbor vastly more species per acre than the higher latitudes, where species are physiologically broadly adapted, and consequently distributed over far greater ranges. Thus, a species with huge populations spread out over a large area can suffer huge reductions in numbers, yet still be nowhere near total annihilation. Tropical species are much more narrowly adapted and narrowly restricted in geographic range so that the same amount of habitat destruction in the Tropics accounts for many times more species extinctions than would occur in the higher latitudes. The conclusion seems clear: Ongoing, unrelenting habitat destruction is driving thousands of species to extinction each year -- species that for the most part we haven't even come to know as yet. Direct destruction of ecosystems is having a mounting effect on ecosystem services, which are vital to our quality of life and our continued ability to elude extinction. APPRECIATING THE BENEFITS OF PLANT BIODIVERSITY By John Tuxill From "State of the World, 1999." Copyright ? 1999, Worldwatch Institute. Publication is available from Worldwatch Institute, 1776 Massachusetts Avenue, N.W., Washington, D.C. 20036. http://www.worldwatch.org At first glance, wild potatoes are not too impressive. Most are thin-stemmed, rather weedy-looking plants that underground bear disappointingly small tubers. But do not be deceived by initial appearances, for these plants are key allies in humankind's ongoing struggle to control late blight, a kind of fungus that thrives on potato plants. It was late blight that, in the 1840s, colonized and devastated the genetically uniform potato fields of Ireland, triggering the infamous famine that claimed more than a million lives. The disease has been controlled this century largely with fungicides, but in the mid-1980s farmers began reporting outbreaks of fungicide-resistant blight. These newly virulent strains have cut global potato harvests in the 1990s by 15 percent, a $3.25 billion [thousand-million] yield loss; in some regions, such as the highlands of Tanzania, losses to blight have approached 100 percent. Fortunately, scientists at the International Potato Center in Lima, Peru, have located genetic resistance to the new blight strains in the gene pools of traditional Andean potato cultivars and their wild relatives, and now see hope for reviving the global potato crop. Wild potatoes are but one manifestation of the benefits humans gain from biological diversity, the richness and complexity of life on Earth. Plant biodiversity, in particular, is arguably the single greatest resource that humankind has garnered from nature during our long cultural development. Presently, scientists have described more than 250,000 species of mosses, ferns, conifers, and flowering plants, and estimate there may be upwards of 50,000 plant species yet to be documented, primarily in the remote, little-studied reaches of tropical forests. Within just the hundred-odd species of cultivated plants that supply most of the world's food, traditional farmers have selected and developed hundreds of thousands of distinct genetic varieties. During this century, professional plant breeders have used this rich gene pool to create the high-yielding crop varieties responsible for much of the enormous productivity of modern farming. Plant diversity also provides oils, latexes, gums, fibers, dyes, essences, and other products that clean, clothe, and refresh us and that have many industrial uses. And whether we are in the 20 percent of humankind who open a bottle of pills when we are feeling ill, or in the 80 percent who consult a local herbalist for a healing remedy, a large chunk of our medicines comes from chemical compounds produced by plants. Yet the more intensively we use plant diversity, the more we threaten its long-term future. The scale of human enterprise on Earth has become so great -- we are now nearly 6 billion strong and consume about 40 percent of the planet's annual biological productivity -- that we are eroding the very ecological foundations of plant biodiversity and losing unique gene pools, species, and even entire communities of species forever. It is as if humankind is painting a picture of the next millennium with a shrinking palette -- the world will still be colored green, but in increasingly uniform and monocultured tones. Of course, our actions have produced benefits: society now grows more food than ever before, and those who can purchase it have a material standard of living unimaginable to earlier generations. But the undeniable price that plant diversity and the ecological health of our planet are paying for these achievements casts a shadow over the future of the development path that countries have pursued this century. To become more than a short-term civilization, we must start by maintaining biological diversity. INTO THE MASS EXTINCTION Extinction is a natural part of evolution, but it is normally a rare and obscure event; the natural or "background" rate of extinction appears to be about 1-10 species a year. By contrast, scientists estimate that extinction rates have accelerated this century to at least 1,000 species per year. These numbers indicate we now live in a time of mass extinction -- a global evolutionary upheaval in the diversity and composition of life on Earth. Paleontologists studying Earth's fossil record have identified five previous mass extinction episodes during life's 1.5 billion years of evolution, with the most recent being about 65 million years ago, at the end of the Cretaceous period, when the dinosaurs disappeared. Earlier mass extinctions hit marine invertebrates and other animal groups hard, but plants weathered these episodes with relatively little trouble. Indeed, flowering plants, which now account for nearly 90 percent of all land plant species, did not begin their diversification until the Cretaceous -- relatively recently, in evolutionary terms. In the current mass extinction, however, plants are suffering unprecedented losses. According to a 1997 global analysis of more than 240,000 plant species coordinated by the World Conservation Union-IUCN, one out of every eight plants surveyed is potentially at risk of extinction. This tally includes species already endangered or clearly vulnerable to extinction, as well as those that are naturally rare (and thus at risk from ecological disruption) or extremely poorly known. More than 90 percent of these at-risk species are endemic to a single country -- that is, found nowhere else in the world. The United States, Australia, and South Africa have the most plant species at risk, but their high standing is partly due to how much better-known their flora is compared with that of other species-rich countries. We have a good idea of how many plants have become endangered as the coastal sage scrub and perennial grasslands of California have been converted into suburban homes and cropland, for example. But we simply do not know how many species have dwindled as the cloud forests of Central America have been replaced by coffee plots and cattle pastures, or as the lowland rainforests of Indonesia and Malaysia have become oil palm and pulpwood plantations. Increasingly, it is not just individual species but entire communities and ecosystems of plants that face extinction. The inter-Andean laurel and oak forests of Colombia, the heath-lands of western Australia, the seasonally dry forest of the Pacific island of New Caledonia -- all have been largely overrun by humankind. In the southeast corner of Florida in the United States, native plant communities, such as subtropical hardwood hammocks and limestone ridge pinelands, have been reduced to tiny patches in a sea of suburban homes, sugarcane fields, and citrus orchards. These irreplaceable remnants are all that is left of what southeast Florida once was -- and they are now held together only with constant human vigilance to beat back a siege of exotic plants, such as Brazilian pepper and Australian casuarina. Biodiversity is also lost when gene pools within species evaporate. The closest wild ancestor of corn is a lanky, sprawling annual grass called teosinte, native to Mexico and Guatemala, where it occurs in eight separate populations. Botanist Garrison Wilkes of the University of Massachusetts regards seven of these populations as rare, vulnerable, or already endangered -- primarily due to the abandonment of traditional agricultural practices and to increased livestock grazing in the field margins and fallow areas favored by teosinte. Overall, teosinte is not yet threatened with extinction. But because the plant hybridizes readily with domesticated corn, every loss of a unique teosinte population reduces genetic diversity that may one day be needed to breed better-adapted corn plants. OF FOOD AND FARMERS Nowhere is the value of biodiversity more evident than in our food supply. Roughly one third of all plant species have edible fruits, tubers, nuts, seeds, leaves, roots, or stems. During the nine tenths of human history when everyone lived as hunter-gatherers, an average culture would have had knowledge of several hundred edible plant species that could provide sustenance. Today, wild foods continue to supplement the diet of millions of rural poor worldwide, particularly during seasonal periods of food scarcity. Tuareg women in Niger, for instance, regularly harvest desert panic-grass and shama millet while migrating with their animal herds between wet and dry-season pastures. In rural northeast Thailand, wild foods gathered from forests and field margins make up half of all food eaten by villagers during the rainy season. In the city of Iquitos in the Peruvian Amazon, fruits of nearly 60 species of wild trees, shrubs, and vines are sold in the city produce markets. Residents in the surrounding countryside are estimated to obtain a tenth of their entire diet from wild-harvested fruits. For the last 5-10 millennia, we have actively cultivated the bulk of our food. Agriculture arose independently in many different regions, as people gradually lived closer together, became less nomadic, and focused their food production on plants that were amenable to repeated sowing and harvesting. In the 1920s, the legendary Russian plant explorer Nikolai Vavilov identified geographic centers of crop diversity, including Mesoamerica, the central Andes, the Mediterranean Basin, the Near East, highland Ethiopia, and eastern China. He also inferred correctly that most centers correspond to where crops were first domesticated. For instance, native Andean farmers not only brought seven different species of wild potatoes into cultivation, they also domesticated common beans, lima beans, passion fruit, quinoa and amaranths (both grains), and a host of little-known tuber and leaf crops such as oca, ulluco, and tarwi -more than 25 species of food plants in all. Over the millennia, farmers have developed a wealth of distinctive varieties within crops by selecting and replanting seeds and cuttings from uniquely favorable individual plants -- perhaps one that matured slightly sooner than others, was unusually resistant to pests, or possessed a distinctive color or taste. Subsistence farmers have always been acutely attentive to such varietal diversity because it helps them cope with variability in their environment, and for most major crops, farmers have developed thousands of folk varieties, or "landraces." India alone, for instance, probably had at least 30,000 rice landraces earlier this century. On-farm crop selection remains vital in developing countries, where farmers continue to save 80-90 percent of their own seed supplies. In industrial nations, by contrast, the seed supply process has become increasingly centralized during this century, as professional plant breeders have taken up the job of crop improvement and as corporations have assumed responsibility for supplying seeds. The power and promise of scientifically based plant breeding was confirmed by the 1930s, when the first commercial hybrid corn was marketed by the Pioneer Hi-Bred Company. Hybrids are favored by seed supply companies because they tend to be especially high-yielding (the bottom line for commercial farming) and because "second-generation" hybrid seeds do not retain the traits of their parents. This means that farmers must purchase hybrid seed anew from the supplier rather than saving their own stock. Some farmers have also been legally disenfranchised from seed-saving; under European Union law, it is now illegal for farmers to save and replant seed from plant varieties that have been patented by breeders. Although farmers can now purchase and plant seeds genetically engineered with the latest molecular techniques, the productivity of our food supply still depends on the plant diversity maintained by wildlands and traditional agricultural practices. Wild relatives of crops continue to be used by breeders as sources of disease resistance, vigor, and other traits that produce billions of dollars in benefits to global agriculture. Imagine giving up sugarcane, strawberries, tomatoes, and wine grapes; none of these crops could be grown commercially without the genetic contribution of their respective wild relatives. With the rescue mission of their wild kin now under way, we can also place potatoes on this list. Traditional crop varieties are equally indispensable for global food security. Subsistence farmers around the world continue to grow primarily either landraces or locally adapted versions of professionally bred seed. Such small-scale agriculture produces 15-20 percent of the world's food supply, is predominantly performed by women, and provides the daily sustenance of roughly 1.4 billion rural poor. Moreover, landraces have contributed the genetic infrastructure of the intensively bred crop varieties that feed the rest of us. More than one third of the U. S. wheat crop owes its productivity to landrace genes from Asia and other regions, a contribution worth at least $500 million annually. As we enter the next millennium, agricultural biodiversity faces an uncertain future. The availability of wild foods and populations of many wild relatives of crops is declining as wildlands are converted to human-dominated habitats and as hedgerows, fallow fields, and other secondary habitats decline within traditional agricultural landscapes. In the United States, two thirds of all rare and endangered plants are close relatives of cultivated species. If these species go extinct, a pool of potentially crucial future benefits for global agriculture will also vanish. There is also grave concern for the old crop landraces. By volume, the world's farmers now grow more sorghum, spinach, apples, and other crops than ever before, but they grow fewer varieties of each crop. Crop diversity in industrial nations has undergone a massive turnover this century; the proportion of varieties grown in the United States before 1904 but no longer present in either commercial agriculture or any major seed storage facility ranges from 81 percent for tomatoes to over 90 percent for peas and cabbages. Figures are less comprehensive for developing countries, but China is estimated to have gone from growing 10,000 wheat varieties in 1949 to only 1,000 by the 1970s, while just 20 percent of the corn varieties cultivated in Mexico in the 1930s can still be found there -- an alarming decline for the cradle of corn. Crop varieties are lost for many reasons. Sometimes an extended drought destroys harvests and farmers must consume their planting seed stocks just to survive. Long- term climate change can also be a problem. In Senegal, two decades of below-normal rainfall created a growing season too short for traditional rice varieties to produce good yields. When fast-maturing rice cultivars became available through development aid programs, women farmers rapidly adopted them because of the greater harvest security they offered. In the majority of cases, however, farmers voluntarily abandon traditional seeds when they adopt new varieties, change agricultural practices, or move out of farming altogether. In industrial countries, crop diversity has declined in concert with the steady commercialization and consolidation of agriculture this century: fewer family farmers, and fewer seed companies offering fewer varieties for sale, mean fewer crop varieties planted in fields or saved after harvest. The seed supply industry is now dominated by multinational corporations; increasingly, the same companies that sell fertilizers and pesticides to farmers now also promote seeds bred to use those products. In most developing countries, diversity losses were minimal until the 1960s, when the famed international agricultural development program known as the Green Revolution introduced new high-yielding varieties of wheat, rice, corn, and other major crops. Developed to boost food self-sufficiency in famine-prone countries, the Green Revolution varieties were widely distributed, often with government subsidies to encourage their adoption, and displaced landraces from many prime farmland areas. In areas where agriculture is highly mechanized and commercialized, crops now exhibit what the U.N. Food and Agriculture Organization (FAO) politely calls an "impressively uniform" genetic base. A survey of nine major crops in the Netherlands found that the three most popular varieties for each crop covered 81-99 percent of the respective areas planted. Such patterns have also emerged on much of the developing world's prime farmland. One single wheat variety blanketed 67 percent of Bangladesh's wheat acreage in 1983 and 30 percent of India's the following year. The ecological risks we take in adopting such genetic uniformity are enormous, and keeping them at bay requires an extensive infrastructure of agricultural scientists and extension workers -- as well as all too frequent applications of pesticides and other potent agrochemicals. A particularly heavy burden falls on professional plant breeders, who are now engaged in a relay race to develop ever more robust crop varieties before those already in monoculture succumb to evolving pests and diseases, or to changing environmental conditions. Breeders started this race earlier this century with a tremendous genetic endowment at their disposal, courtesy of nature and generations of subsistence farmers. Despite major losses, this wellspring is still far from empty -- estimates are that plant breeders have used only a small fraction of the varietal diversity present in crop gene banks (facilities that store seeds under cold, dry conditions that can maintain seed viability for decades). At the same time, we can never be sure that what is already stored will cover all our future needs. When grassy stunt virus began attacking high-yielding Asian rices in the 1970s, breeders located genetic resistance to the disease in only a single collection of one population of a wild rice species in Uttar Pradesh, India -- and that population has never been found again since. Conserving and reinvigorating biodiversity in agricultural landscapes remains essential for achieving global food security. OF MEDICINES AND MATERIAL GOODS In a doctor's office in Germany, a man diagnosed with hypertension is prescribed reserpine, a drug from the Asian snakeroot plant. In a small town in India, a woman complaining of stomach pains visits an ayurvedic healer, and receives a soothing and effective herbal tea as part of her treatment. In a California suburb, a headache sufferer unseals a bottle of aspirin, a compound originally isolated from European willow trees and meadow herbs. People everywhere rely on plants for staying healthy and extending the quality and length of their lives. One quarter of the prescription drugs marketed in North America and Europe contain active ingredients derived from plants. Plant-based drugs are part of standard medical procedures for treating heart conditions, childhood leukemia, lymphatic cancer, glaucoma, and many other serious illnesses. Worldwide, the overthe-counter value of these drugs is estimated at more than $40 billion annually. Major pharmaceutical companies and institutions such as the U.S. National Cancer Institute implement plant screening programs as a primary means of identifying new drugs. The World Health Organization estimates that 3.5 billion people in developing countries rely on plant-based medicine for their primary health care. Ayurvedic and other traditional healers in South Asia use at least 1,800 different plant species in treatments and are regularly consulted by some 800 million people. In China, where medicinal plant use goes back at least four millennia, healers employ more than 5,000 plant species. At least 89 plant-derived commercial drugs used in industrial countries were originally discovered by folk healers, many of whom are women. Traditional medicine is particularly important for poor and rural residents, who typically are not well served by formal health care systems. Recent evidence suggests that when economic woes and structural adjustment programs restrict governments' abilities to provide health care, urban and even middle-class residents of developing countries also turn to more affordable traditional medicinal experts. Traditional herbal therapies are growing rapidly in popularity in industrial countries as well. FAO estimates that between 4,000 and 6,000 species of medicinal plants are traded internationally, with China accounting for about 30 percent of all such exports. In 1992, the booming U.S. retail market for herbal medicines reached nearly $1.5 billion, and the European market is even larger. Despite their demonstrable value, medicinal plants are declining in many areas. Human alteration of forests and other habitats all too often eliminates sites rich in wild medicinal plants. This creates an immediate problem for folk healers when they can no longer find the plants they need for performing certain cures -- a problem commonly lamented by indigenous herbalists in eastern Panama, among others. Moreover, strong consumer demand and inadequate oversight of harvesting levels and practices mean that wild-gathered medicinal plants are commonly overexploited. In Cameroon, for example, the bark of the African cherry is highly esteemed by traditional healers, but most of the country's harvest is exported to Western Europe, where African cherry is a principal treatment for prostate disorders. In recent years Cameroon has been the leading supplier of African cherry bark to international markets, but clearance of the tree's montane forest habitat, combined with the inability of the government forestry department to manage the harvest, has led to widespread, wanton destruction of cherry stands. In addition to the immediate losses, every dismantling of a unique habitat represents a loss of future drugs and medicines, particularly in species-rich habitats like tropical forests. Fewer than 1 percent of all plant species have been screened by chemists to see what bioactive compounds they may contain. The nearly 50 drugs already derived from tropical rainforest plants are estimated to represent only 12 percent of the medically useful compounds waiting to be discovered in rainforests. Most tragically of all, many rural societies are rapidly losing their cultural knowledge about medicinal plants. In communities undergoing accelerated westernization, fewer young people are interested in learning about traditional healing plants and how to use them. From Samoa to Suriname, most herbalists and healers are elderly, and few have apprentices studying to take their place. Ironically, as this decline has accelerated, there has been a resurgent interest in ethnobotany -- the study of how people classify, conceptualize, and use plants -- and other fields of study related to traditional medicinal plant use. Professional ethnobotanists surveying medicinal plants used by different cultures are racing against time to document traditional knowledge before it vanishes with its last elderly practitioners. For the one quarter of humanity who live at or near subsistence levels, plant diversity offers more than just food security and health care -- it also provides a roof over their heads, cooks their food, provides eating utensils, and on average meets about 90 percent of their material needs. Consider palms: temperate zone dwellers may think of palm trees primarily as providing an occasional coconut or the backdrop to an idyllic island vacation, but tropical peoples have a different perspective. The babassu palm from the eastern Amazon Basin has more than 35 different uses -- construction material, oil and fiber source, game attractant, even as an insect repellent. Commercial extraction of babassu products is a part or fulltime economic activity for more than 2 million rural Brazilians. Indigenous peoples throughout tropical America have been referred to as "palm cultures." The posts, floors, walls, and beams of their houses are made from the wood of palm trunks, while the roofs are thatched with palm leaves. They use baskets and sacks woven from palm leaves to store household items, including food -- which may itself be palm fruits, palm hearts (the young growing shoot of the plant), or wild game hunted with weapons made from palm stems and leaves. At night, family members will likely drift off to sleep in hammocks woven from palm fibers. When people die, they may be buried in a coffin carved from a palm trunk. Palms are exceptionally versatile, but they are only part of the spectrum of useful plants in biodiverse environments. In northwest Ecuador, indigenous cultures that practice shifting agriculture use more than 900 plant species to meet their material, medicinal, and food needs; halfway around the world, Dusun and Iban communities in the rainforests of central Borneo use a similar total of plants in their daily lives. People who are more integrated into regional and national economies tend to use fewer plants, but still commonly depend on plant diversity for household uses and to generate cash income. In India, at least 5.7 million people make a living harvesting non-timber forest products, a trade that accounts for nearly half the revenues earned by Indian state forests. Those of us who live in manicured suburbs or urban concrete jungles may meet more of our material needs with metals and plastics, but plant diversity still enriches our lives. Artisans who craft musical instruments or furniture, for instance, value the unique acoustic qualities and appearances of the different tropical and temperate hardwoods that they work with -- aspects of biodiversity that ultimately benefit anyone who listens to classical music or purchases handcrafted furniture. Among the nonfood plants traded internationally on commercial levels are at least 200 species of timber trees, 42 plants producing essential oils, 66 species yielding latexes or gums, and 13 species used as dyes and colorants. As with medicinals, the value that plant resources have for handicraft production, industrial use, or household needs has often not prevented their local or regional decline. One of the most valuable non-timber forest products is rattan, a flexible cane obtained from a number of species of vine-like palms that can grow up to 185 meters long. Asian rattan palms support an international furniture-making industry worth $3.5-6.5 billion annually. Unfortunately, rattan stocks are declining throughout much of tropical Asia because of the loss of native rainforest and over-harvesting. In the past few years, some Asian furniture makers have even begun importing rattan supplies from Nigeria and other central African countries. On a global level, declines of wild plants related to industrial crops such as cotton or plantation-grown timber could one day limit our ability to cultivate those commodities by shrinking the gene pools needed for breeding new crops. More locally, declines of materially useful species mean life gets harder and tougher in the short term. When a tree species favored for firewood is over-harvested, women must walk longer to collect their family's fuel supply, make due with an inferior species that does not burn as well, or spend scarce money purchasing fuel from vendors. When a fiber plant collected for sale to handicraft producers becomes scarce, it is harder for collectors to earn an income that could help pay school fees for their children. Whether we are rich or poor, biodiversity enhances the quality of our lives -- and many people already feel its loss. BIO-UNIFORMITY RISING The cumulative effects of human activities on Earth are evident not just in declines in particular species, but in the increasingly tattered state of entire ecosystems and landscapes -- and when large-scale ecological processes begin to break down, conservation and management become all the more complicated. Take the problem of habitat fragmentation, when undisturbed wildlands are reduced to patchwork, islandlike remnants of their former selves. Natural islands in oceans or large lakes tend to be impoverished in species; their smaller area means they usually do not develop the ecological complexity and diversity characteristic of more extensive mainland areas. Moreover, when an island population of a species is eradicated, it is harder for adjacent mainland populations to recolonize and replace it. As a result, when development -- large-scale agriculture, settlements, roads -- sprawls across landscapes, remaining habitat fragments usually behave like the islands they have become: they lose species. In western Ecuador, the R�Palenque Science Center protects a square-kilometer remnant of the lowland rainforest that covered the region a mere three decades ago; now the center is an island amid cattle pasture and oil palm plantations. Twenty-four species of orchids, bromeliads, and other plants at R�Palenque have already succumbed to the "island effect" and can no longer be found there. One vanished species, an understory shrub, has never been recorded anywhere else and is presumed extinct. Even with these drawbacks, small areas of native habitat can have enormous conservation value when they are all that is left of a unique plant community or rare habitat. But waiting to protect them until only patches remain carries an unmistakable tradeoff: smaller holdings require more intensive management than larger ones. In smaller reserves, managers often must simulate natural disturbances (such as prescribed burns to maintain fire-adapted vegetation); provide pollination, seed dispersal, and pest control services in place of vanished animals; reintroduce desirable native species when they disappear from a site (perhaps due to a series of poor breeding seasons); and perform other duties the original ecosystem once did free of charge. Governments and societies that are unwilling or unable to shoulder these management costs will soon find that the biodiversity they intended to protect with nature reserves has vanished from within them. Invasive species that crowd out native flora and fauna are one of the biggest headaches for managing biodiversity in disturbed landscapes. In certain susceptible habitats, such as oceanic islands and subtropical heathlands, controlling invasives may be the single biggest management challenge. South Africa has one of the largest invasive species problems of any nation, and has a great deal at stake: the fynbos heathlands and montane forest of the country's Cape region hold more plant species -8,600, most of them endemic -- in a smaller area than anywhere else on Earth. Fortunately, South Africans are increasingly aware of the threat that exotics pose, and in 1996 the government initiated a program to fight invasives with handsaw and hoe. Some 40,000 people are employed to cut and clear Australian eucalypts, Central American pines, and other unwanted guests in natural areas. It is a measure of the scale and severity of the invasive problem that this effort is South Africa's single largest public works program. Large-scale ecological alterations also have great potential to combine their effects in unpredictable and damaging ways. For instance, much of the world is now saturated in nitrogen compounds (an essential element required by all plants for growth and development) because of our overuse of nitrogen-based synthetic fertilizers and fossil fuels. Studies of North American prairies found that the plants that responded best to excess nitrogen tended to be weedy invasives, not the diverse native prairie flora. Likewise, plant and animal species already pressed for survival in fragmented landscapes may also have to contend with altered rainfall patterns, temperature ranges, seasonal timing, and other effects of global climate change. Already, scientists are detecting what could be the first fingerprints of an altered global atmosphere on plant communities. Data from tropical forest research plots worldwide indicate that the rate at which rainforest trees die and replace each other, called the turnover rate, has increased steadily since the 1950s. This suggests that the forests under study are becoming "younger," increasingly dominated by faster-growing, shorter-lived trees and woody vines -- exactly the kinds of plants expected to thrive in a carbon dioxide-rich world with more extreme weather events. Without major reductions in global carbon emissions, forest turnover rates will likely rise further, and over time could push to extinction many slower-growing tropical hardwood tree species that cannot compete in a carbon-enriched environment. Global trends are shaping a botanical world that is most striking in its greater uniformity. The richly textured mix of native plant communities that evolved over thousands of years is increasingly frayed, replaced by extensive areas under intensive cultivation or heavy grazing, lands devoted to settlements or industrial activities, and secondary habitats -- partially disturbed areas dominated by shorter-lived, "weedy," often nonnative species. A 1994 mapping study by the organization Conservation International estimated that nearly three quarters of our planet's habitable land surface (that which is not bare rock, drifting sand, or ice) already is either partially or heavily disturbed. Moreover, within human-dominated landscapes, relatively diverse patchworks of small-scale cultivation, fallow fields, seasonal grazing areas, and managed native vegetation are being replaced by large, uniform fields or by extensive denuded and degraded areas. The mixtures of species in different regions are becoming more similar as well. Lists of endangered plants are dominated by endemic species -- those native to a relatively restricted area such as a country or state, an isolated mountain range, or a specific soil type. When endemic plants vanish, the remaining species pool becomes more uniform. Finally, the spectrum of distinct populations and varieties within plant species is shrinking, a problem most advanced in our endowment of domesticated plants. Countries that emerged in a world filled with biodiversity now must gain and maintain prosperity amid increasing bio-uniformity. We are conducting an unprecedented experiment with the security and stability of our food supply, our health care systems, and the ecological infrastructure upon which both rest. To obtain the results we desire, we must conserve and protect the plant biodiversity that remains with us, and manage our use of natural systems in ways that restore biodiversity to landscapes worldwide. STORED FOR SAFEKEEPING Broad recognition of the need to safeguard plant resources is largely a twentieth century phenomenon. The first warnings about the global erosion of plant diversity were voiced in the 1920s by scientists such as Harry Harlan of the United States and Nikolai Vavilov, who realized the threat posed by farmers' abandonment of landraces in favor of newer varieties that were spreading widely in an increasingly interconnected world. The dominant approach to conserving plant varieties and species has involved removing them from their native habitat or agricultural setting and protecting them at specialized institutions such as botanical gardens, nurseries, and gene banks. Most offsite collections of wild species and ornamental plants are in the custody of the world's 1,600 botanical gardens. Combined, they tend representatives of tens of thousands of plant species -- nearly 25 percent of the world's flowering plants and ferns, by one estimate. Most botanical gardens active today were established by European colonial powers to introduce economically important and ornamental plants throughout the far-flung reaches of empires, and to promote the study of potentially useful plants. Nowadays many botanical gardens have reoriented their mission toward species preservation, particularly in their research and education programs. Since the late 1980s, botanical gardens have coordinated efforts through an international conservation network, which helps ensure that the rarest plants receive priority for propagation and, ultimately, reintroduction. Gene banks have focused almost exclusively on storing seeds of crop varieties and their immediate wild relatives. (The principal exception is the Royal Botanic Garden's Millennium Seed Bank in England, which holds more than 4,000 wild species and is expanding toward a collection of one quarter of the world's flora.) Gene banks arose from plant breeders' need to have readily accessible stocks of breeding material. Their conservation role came to the forefront in the 1970s, following large losses linked to genetic uniformity in the southern U.S. corn crop in 1970 and the Soviet winter wheat crop of 1971-72. In 1974, governments and the United Nations established the International Board for Plant Genetic Resources (now known as the International Plant Genetic Resources Institute, or IPGRI), which cobbled together a global network of gene banks. The network includes university breeding programs, government seed storage units, and the Consultative Group on International Agricultural Research (CGIAR), a worldwide network of 16 agricultural research centers originally established to bring the Green Revolution to developing countries, and funded primarily by the World Bank and international aid agencies. The number of unique seed samples or "accessions" in gene banks now exceeds 6 million. The largest chunk of these, more than 500,000 accessions, are in the gene banks of CGIAR centers such as the International Rice Research Institute in the Philippines and the International Wheat and Maize Improvement Center (CIMMYT) in Mexico. At least 90 percent of all gene bank accessions are of food and commodity plants, especially the world's most intensively bred and economically valuable crops. By the late 1980s, IPGRI regarded a number of these crops, such as wheat and corn, as essentially completely collected; that is, nearly all of the known landraces and varieties of the crop are already represented in gene banks. Others have questioned this assessment, however, arguing that the lack of quantitative studies of crop gene pools makes it difficult to ascertain whether even the best-studied crops have been adequately sampled. There are additional reasons for interpreting gene bank totals conservatively. The total annual cost of maintaining all accessions currently in gene banks is about $300 million, and many facilities, hard-pressed for operating funds, cannot maintain seeds under optimal physical conditions. Seeds that are improperly dried or kept at room temperature rather than in cold storage may begin to lose viability within a few years. At this point, they must be "grown out" -- germinated, planted, raised to maturity, and then reharvested, which is a time-consuming and labor-intensive activity when repeated for thousands of accessions per year. These problems suggest that an unknown fraction of accessions is probably of questionable viability. Only 13 percent of gene-banked seeds are in well-run facilities with long-term storage capability -- and even the crown jewels of the system, such as the U. S. National Seed Storage Laboratory, have at times had problems maintaining seed viability rates. For extensively gene-banked crops (primarily major grains and legumes) where large collections are duplicated in different facilities, the odds of losing the diversity already on deposit are reduced. But for sparsely collected crops whose accessions are stored at just one or two sites, the possibility of genetic erosion remains disquietingly high. Despite such drawbacks, offsite facilities remain indispensable for conservation. In some cases, botanical gardens and gene banks have rescued species whose wild populations are now gone. They can also help return diversity to its proper home through reintroduction programs. Although the uplands of East Africa are not the center of domestication for common beans, the farmers of the region adopted them as their own several centuries ago, and have developed the world's richest mix of local bean varieties. When Rwanda was overwhelmed by civil conflict in 1994, the height of the genocidal violence occurred during the February-to-June growing season, greatly reducing harvests and raising the prospect of widespread famine. Amid the relief contributions that flowed into the country once the situation had stabilized were stocks of at least 170 bean varieties that had been previously collected in Rwanda and stored in gene banks worldwide. These supplies helped ensure that Rwandan farmers had stocks of high-quality, locally adapted beans for planting in the subsequent growing season. Still, even the most enthusiastic boosters of botanical gardens and gene banks recognize that such facilities, even when impeccably maintained, provide only one piece in the conservation puzzle. Offsite storage takes species out of their natural ecological settings. Wild tomato seeds can be sealed in a glass jar and frozen for safekeeping, but left out of the cold are the plant's pollinators, its dispersers, and all the other organisms and relationships that have shaped the plant's unique evolution. Gene banks and botanical gardens only save a narrow -- albeit valuable -- slice of plant diversity. When stored seeds are grown out over several generations offsite, in time they can even lose their native adaptations and evolve to fit instead the conditions of their captivity. KEEPING DIVERSITY IN PLACE In the end, plant diversity can be securely maintained only by protecting the native habitats and ecosystems where plants have evolved. Countries have safeguarded wildlands primarily through establishing national parks, forest reserves, and other formally protected areas. During this century, governments have steadily increased protected area networks, and they now encompass nearly 12 million square kilometers, or about 8 percent of the Earth's land surface. Many protected areas guard irreplaceable botanical resources, such as Malaysia's Mount Kinabalu National Park, which safeguards the unique vegetation of southeast Asia's highest peak. A few reserves have been established specifically to protect useful plants, such as the Sierra de Manantlan biosphere reserve in Mexico, which encompasses the only known populations of perennial wild corn. Yet current protected area networks also have major limitations. Many highly diverse plant communities, such as tropical deciduous forests, are greatly under-protected. In addition, many protected areas officially decreed on paper are minimally implemented by chronically underfunded and understaffed natural resource agencies. But perhaps the most fundamental limitation of national parks, wilderness areas, and similarly strict designations arises when they conflict with the cultural and economic importance that plants hold for local communities. A great deal of the natural wealth that conservationists have sought to protect is actually on lands and under waters long managed by local people. Indigenous societies worldwide have traditionally protected prominent landscape features like mountains or forests, designating them as sacred sites and ceremonial centers. In parts of West Africa, sacred groves hold some of the last remaining populations of important medicinal plants. On Samoa and other Pacific islands, communities manage forests to produce wild foods and medicines, raw materials for canoes and household goods, and other benefits. Not surprisingly, actions such as evicting long-term residents from newly designated forest reserves, or denying them access to previously harvested plant stands, have generated a great deal of ill will toward protected areas worldwide. Fortunately, workable alternatives are emerging in a number of cases where long-term residents have been made equal partners in managing protected lands. In the Indian state of West Bengal, 320,000 hectares of semideciduous sal forest is managed jointly by villagers and the state forestry department, with villagers taking primary responsibility for patrolling nearby forest stands. Since joint management began in 1972, the status of the sal forests has improved, and regenerating stands now provide villagers with medicines, firewood, and wild-gathered foodstuffs. Medicinals also feature prominently in a 4,000-hectare rainforest reserve in Belize, which is government-owned but managed by the Belize Association of Traditional Healers. Such collaboration between locals and professional resource managers is also crucial to reversing the overexploitation of valuable wild plants. Very few commercially marketed wild species are harvested sustainably, in ways or at levels that do not degrade the plant resource. Despite the lack of progress, however, the foundations of sustainability are becoming increasingly clear. Secure and enforceable tenure is essential -- either in the form of rights to harvest a plant or tenure over the land it grows on. Harvesters also need enough economic security to be able to afford the tradeoffs involved in not harvesting everything at once. Access to fair and open markets is important, as is having technology appropriate for the harvesting task. Information about the ecology and productivity of a plant can make a big difference. Consumers willing to pay a premium for well-harvested products also help -- like those generated through certification programs for "environmentally friendly" products. Few wild harvests meet all these criteria, but a growing number of initiatives are coming close. In Mexico, ancient cone-bearing plants called cycads have been heavily exploited for their ornamental value, both for sale domestically and for horticultural export to the United States, Japan, and Europe. Most cycads are wild-harvested by uprooting or cutting, but a botanical garden in the state of Veracruz is working with local villagers to reduce pressures on several overexploited species. In one community, Monte Oscuro, residents set aside a communal plot of dry forest to protect a relict population of cycads in exchange for help with building a community plant nursery. Seeds are collected from the wild plants, then germinated and tended in the nursery by villagers who have received training in basic cycad propagation. Some of the young cycads are returned to the forest to offset any potential downturn in the wild population from the seed harvest. The rest are sold and the profits deposited in a community fund. Presently the largest hurdle is finding good markets for the young plants the communities are producing; cycads are slow-growing, and horticultural buyers prefer larger plants. Better monitoring and enforcement of the international ornamental plant trade would help, for Mexican cycad species are listed with the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) of 1973, which provides a powerful legal tool for controlling international trade in threatened plants and animals. CITES is generally regarded as one of the more effective international environmental treaties. It prohibits trade in the most highly endangered species (listed in the Treaty's Appendix I), and keeps watch on vulnerable species (listed in Appendix II) by requiring that countries issue a limited number of permits for the species' export and import between signatory countries. Although CITES provides powerful tools for enforcing sustainable harvests, it is still up to the countries involved to use them. Combining local and international strengths also is crucial for sustaining the genetic diversity of our food supply. What is needed most is agricultural development that strengthens rather than simplifies plant diversity to meet the needs and goals of farmers -- especially subsistence farmers in developing countries who still maintain diverse agricultural landscapes. Meeting this challenge requires understanding the particular cultural, economic, and technological reasons why farmers maintain elements of traditional farming, such as unique crop variety mixtures. For instance, native Hopi communities in the southwest United States maintain indigenous corn and lima bean varieties because the germinating seeds are indispensable for religious ceremonies. Mende farmers in Sierra Leone continue to grow native red-hulled African rice for the same reason. Andean peasant farmers still grow pink and purple potatoes, big-seed corn, quinoa, and other traditional crops because that is what they themselves prefer to eat; the commercial varieties they grow are strictly to sell for cash income. One option to help farmers maintain crop diversity could involve supporting farmers' informal networks of seed exchange and procurement, so as to improve their access to diverse seed sources. In some rural communities in Zimbabwe, villagers contribute seeds annually to a community seed stock. At the start of the planting season, the seeds are redistributed to all community members, a step that gives villagers access to the full range of varietal diversity present in the immediate vicinity and ensures that no one goes without seeds for planting. Grassroots organizations in Ethiopia, Peru, Tonga, and many other countries have sponsored community seed banks, regional agricultural fairs, seed collection tours, demonstration gardens, and similar projects to promote informal seed exchange between farmers, increase their access to crop diversity, and help them replenish seed stocks after poor harvests. Another approach to maintaining varietal diversity involves reorienting formal plant breeding toward the local needs of farmers. Typically plant breeders create uniform, widely adaptable "purebred" varietal lines, and only toward the end of the process are the lines evaluated with farmers. Participatory plant breeding methods involve farmers at all stages. In the most advanced programs, breeders and farming communities work together over several crop generations to evaluate, select, combine, and improve a wide range of varieties, both those available locally and those from other regions. In this way, participatory plant breeding can improve the suite of locally preferred varieties without resorting to varietal uniformity; this approach maintains -- or potentially even enhances -- the genetic diversity present in farmers' fields. Participatory plant breeding has been pioneered primarily by grassroots development organizations and innovative national plant breeding programs in developing countries; it has not been taken up by commercial seed producers, perhaps because its benefits tend to be diffuse and not easily appropriated for commercial gain. The CGIAR centers are exploring participatory approaches, but also remain heavily involved in standard breeding programs. For instance, the corn and wheat center CIMMYT recently collaborated with university breeders and seed companies to develop better-yielding corn varieties targeted for highland Mexico -- areas where corn landraces continue to be grown by small-scale farmers under diverse environmental conditions. In doing so, CIMMYT chose to focus on hybrid corn varieties. If well tailored to the environmental and economic constraints facing highland Mexican farmers, the new hybrids could boost crop yields -- but farmers will be unable to save their seeds and adapt them further to local conditions. The seed companies involved will surely benefit, but past experience suggests that local plant biodiversity may pay the price. As this last example shows, the most fundamental changes to be made in protecting crop genetic diversity -- and plant biodiversity in general -- involve changing policies. Governments are often biased toward promoting intensive agriculture dependent on high inputs and genetically uniform crops. Farmers in most southern African countries, for instance, are only eligible for government agricultural credit programs if they agree to plant modern improved varieties. International development aid and structural adjustment policies commonly promote nontraditional export crops, which can trigger habitat conversion (erasing wild plant diversity) and replace indigenous crop mixtures. Until fundamental policy changes are taken to heart by governments, international lenders, and related institutions, the path to sustaining plant biodiversity -- wild or domesticated -- will remain difficult. SHARING THE BENEFITS Governments can begin to chart a new course by resolving the most prominent policy issue affecting plant diversity today: how to distribute biodiversity's economic benefits fairly and equitably. Establishing a system of intellectual property rights to plant resources has proved contentious because of a simple pattern -- plant diversity (both wild and cultivated) is held mostly by developing countries, but the economic benefits it generates are disproportionately captured by industrial nations. For most of this century, plant diversity has been treated as the "common heritage" of humankind, freely available to anyone who can use it, with proprietary ownership only granted via patent law to individuals who demonstrate trade secrets or uniquely improve a crop variety or other plant. Since the early 1980s, however, there has been widening agreement that indigenous people and traditional farmers deserve compensation for their long-standing generation, management, and knowledge of biodiversity. Grassroots advocates argue that indigenous people deserve "traditional resource rights" to the plants they cultivate and know how to use, rights that would have the same international legal standing as that afforded to patent rights. Recognition of such rights requires, at a minimum, negotiating equitable benefit-sharing agreements at the community level whenever plants or indigenous knowledge about them is collected by researchers. An additional way to acknowledge the world's debt to rural communities who safeguard plant biodiversity would be to establish an international fund supporting continued local management of plant resources. Such a step appears the most practical means of compensation for the large amount of plant biodiversity that is already in the public domain (such as the millions of seed accessions in gene banks or plants widely used as herbal medicines), since establishing exactly who deserves compensation for commercial innovations from these plant resources is a Herculean task. To date, formal agreements for sharing the benefits of plant diversity have been negotiated most extensively in the search for new pharmaceuticals from plants in biodiversity-rich developing countries. The first such "bioprospecting" agreement was announced in 1991 between Merck Pharmaceuticals and Costa Rica's nongovernmental National Institute of Biodiversity (InBio), in which Merck paid InBio $1.1 million for access to plant and insect samples, and promised to share an undisclosed percentage of royalties from any commercial products that resulted. There are now at least a dozen bioprospecting agreements in place worldwide, involving national governments, indigenous communities, conservation groups, startup companies, and established corporate giants. Most legitimate agreements have followed the Merck-InBio model, with a modest upfront payment and a promise to return between one quarter of 1 percent and 3 percent (depending on the project) of any future royalties to the biodiversity holders. Bioprospecting proponents argue that with the huge cost ($200-350 million) of bringing a new drug to market, companies cannot afford to share a higher percentage of royalties. Critics, however, suspect many bilateral bioprospecting agreements are not negotiated on an even footing; when a biotechnology firm approached the U.S. government about prospecting for unique microbes inhabiting the geysers and hot springs of Yellowstone National Park, for instance, the Park Service negotiated a royalty share of 10 percent. Moreover, not all bioprospecting agreements automatically uphold traditional resource rights; many have been negotiated on a national rather than community level, involving governments who many indigenous people think do not adequately represent -- indeed, sometimes actively undermine -- their interests. In contrast with bioprospecting, resolving who owns the world's crop genetic resources is being negotiated multilaterally, in factious diplomatic arenas. In 1989, FAO adopted a Farmers' Rights proposal that would compensate farmers for their contribution to biodiversity via an international trust fund to support the conservation of plant genetic resources. The 1992 Convention on Biological Diversity also called for incorporating Farmers' Rights, subsequent to further international negotiations. There has been no official endorsement of this concept, however, from the industrial nations who would provide the compensation, and the fund has remained unimplemented? For all of human history, we have depended on plants and the rest of biodiversity for our soul and subsistence. Now the roles are reversed, and biodiversity's fate depends squarely on how we shape our own future. From reducing overexploitation of wild plants to establishing traditional resource rights for biodiversity stewards, many options are available for developing cultural links that support plant diversity rather than diminish it. Such steps are not just about meeting international treaty obligations or establishing new protected areas, but rather are part of a larger process of shaping literate civil societies that are in balance with the natural world. To maintain biodiversity's benefits, what matters most is how well we meet the challenges of living sustainably with our deeds as well as our words. BIBLIOGRAPHY BOOKS Baskin, Yvonne THE WORK OF NATURE: HOW THE DIVERSITY OF LIFE SUSTAINS US Island Press, 1998. Davidson, Osha Gray THE ENCHANTED BRAID: COMING TO TERMS WITH NATURE ON THE CORAL REEF John Wiley & Sons, 1998. Eldredge, Niles LIFE IN THE BALANCE: HUMANITY AND THE BIODIVERSITY CRISIS Princeton, 1998. Raven, Peter H. and Tania Williams, editors NATURE AND HUMAN SOCIETY: THE QUEST FOR A SUSTAINABLE WORLD National Academy of Sciences/National Research Council, 2000. Reaka-Kudla, Marjorie L.; and others, editors BIODIVERSITY II Joseph Henry Press, 1997. Stein, Bruce A.; and others, editors PRECIOUS HERITAGE: THE STATUS OF BIODIVERSITY IN THE UNITED STATES Oxford University Press, 2000 Thorne-Miller, Boyce THE LIVING OCEAN: UNDERSTANDING AND PROTECTING MARINE BIODIVERSITY Island Press, 1999. Wilson, Edward O. THE DIVERSITY OF LIFE W.W. Norton, 1999. ARTICLES Chapin III, F. Stuart; and others "Consequences of Changing Biodiversity" (Nature, Vol. 405, No. 6783, May 11, 2000, pp. 234-242) Cincotta, Richard P.; and Engelman, Robert "Biodiversity and Population Growth" (Issues in Science and Technology, Vol. 16, No. 3, Spring 2000, pp. 80-81) Norris, Scott "A Year for Biodiversity: International Biodiversity Observation Year (IBOY 20012002)" (BioScience, Vol. 50, No. 2, February 2000, pp. 103-107) Tuxill, John "The Biodiversity That People Made--And Are Now Losing" (World Watch, Vol. 13, No. 3, May/June 2000, pp. 24-35) Wilson, Edward O. "A Global Biodiversity Map" (Science, Vol. 289, No. 5488, September 29, 2000, p. 2279) Wilson, Edward O. "Vanishing Before Our Eyes" (Time, Vol. 155, No. 17, Spring 2000, pp. 28-34) Wolfensohn, James D.; Seligmann, Peter A.; and El-Ashry, Mohamed T. "Winning the War on Biodiversity Conservation" (New Perspectives Quarterly, Vol. 17, No. 4, Fall 2000, pp. 38-39) WEB SITES American Museum of Natural History: Biodiversity http://www.amnh.org/science/biodiversity/ Association for Biodiversity Information http://www.abi.org Biodiversity Information Network http://www.bdt.org.br/bin21/ Conservation International http://www.conservation.org Convention on Biological Diversity http://www.biodiv.org Council on Environmental Quality http://www.whitehouse.gov/CEQ Environmental Protection Agency, Ecosystems http://www.epa.gov/ebtpages/ecoterreforests.html Environmental Protection Agency, Office of Water, Oceans http://www.epa.gov/owow/oceans Environmental Protection Agency, Office of Water, Wetlands http://www.epa.gov/owow/wetlands Forest Conservation Portal http://www.forests.org International Coral Reef Initiative http://www.icriforum.org Program for the Conservation of Arctic Flora and Fauna http://www.grida.no/prog/polar/caff/index.htm The Ramsar Convention on Wetlands http://www.ramsar.org U.S. Fish and Wildlife Service http://www.fws.gov U.S. Fish and Wildlife Service Arctic National Wildlife Refuge http://www.r7.fws.gov/nwr/arctic/arctic.html The Virtual Library of Ecology and Biodiversity http://www.conbio.rice.edu/vl/ World Resources Institute: Biological Resources http://www.wri.org/wri/biodiv/ CD ROM Conserving Earth?s Biodiversity. Edward O. Wilson and Dan L. Perlman. Island Press. CORAL REEFS: FERTILE GARDENS OF THE SEA Coral reefs are one of the wonders of nature, because of their enchanting beauty and unusual biology. In addition, many consider them to be second only to tropical rain forests as incubators and protectors of biodiversity. The reefs, which grow in shallow, warm waters, consist largely of the skeletons of small, sedentary animals called polyps, which are relatives of jellyfish and sea anemones. The remains of dead polyps - in the form of calcium carbonate constitute the main body of the reef. Living polyps form a kind of skin over the surface of the coral reef. As they move through their life cycle, coral polyps secrete a hard skeleton or shell of calcium carbonate, into which they contract to protect themselves. When they die, their calcium carbonate remains add to the structure of the reef. For this reason, coral reefs enlarge themselves and become complex structures over the years. Coral polyps begin their lives as larvae floating free. As mature adults, they are sessile animals, that is, they are fixed to one place. They range in size from the diameter of a teacup saucer to a pinhead. Corals feed by reaching out from their perches with tentacles to sting plankton. Their most unusual biological property, however, is a symbiotic relationship they form with a species of algae named of zooxanthellae. The algae infiltrate the bodies of the coral polyps, and use photosynthesis to produce nutrients they share with the polyp. Zooxanthellae can provide up to 90 percent of the nutrition the coral needs to survive. By living in a polyp, the algae receive some protection and are moved closer upwards through the ocean towards the light as the coral structure grows - making it easier for them to perform their photosynthesis. It is the algae that give coral reefs their hues, dramatically reflected by many of the fish and plants and other animals that dwell in and around them. The color pigment given to the polyp by the algae may even work as a kind of sunblock, protecting the polyp from solar radiation. Coral polyps form various kinds of reef structures that have been given names like "brain," "star," and "elkhorn." A non-reef-building coral, "octocoral," can look like trees and shrubs and forms "sea fans" and "sea whips." Coral reefs have been around for about 200 million years, and have survived eons of storm-induced damage and sea animal predation. Unfortunately, their survival in this century is less certain. The year 2000 report from the Global Coral Reef Monitoring Network says that approximately 25 percent of coral reefs worldwide have been effectively lost and another 40 percent "may be lost" by 2010 unless urgent action is taken. Warming oceans, pollution from human activities, damage from careless tourists and fishermen -- even increased ultraviolet radiation from the sun due to the depletion of ozone in the upper atmosphere -- have been blamed for extensive illness and death in the coral population. Corals are uniquely vulnerable because they are near coastlines and near the surface of the ocean. There are fewer healthy coral colonies on the planet than even a few decades ago, according to marine scientists. One of the most frequently studied pathologies is known as "coral bleaching." When stressed by overly warm water, or other causes, coral polyps tend to expel their zooxanthellae, losing their pigment in the process and exposing the white calcium carbonate structure underneath. When this process continues long enough, the reefs become sickly, or die. In a report presented to the U.S. Coral Reef Task Force in 1999, the U.S. State Department warned: "In 1998 coral reefs around the world appear to have suffered the most extensive and severe bleaching and subsequent mortality in modern record. In the same year, tropical sea surface temperatures were the highest in modern record, topping off a 50-year trend for some tropical oceans. These events cannot be accounted for by localized stressors or natural variability alone?. The geographic extent, increasing frequency, and regional severity of mass bleaching events are likely a consequence of a steadily rising baseline of marine temperatures, driven by anthropogenic global warming." Admittedly, corals have natural predators and diseases. But while these and human damage from recreation or fishing are major threats to coral, most observers agree that an altered environment plays a crucial role. In addition to stresses due to changes in ocean temperature, reefs are increasingly exposed to sewage, agricultural runoff, and associated algae blooms near coastal shorelines, themselves the results of human pressure on coastal ecosystems. Sediment that clouds water is bad for coral, and increasing amounts are flowing into the ocean. Unsustainable and damaging fishing practices, including the use of cyanide and explosives to kill fish, trawling, and other forms of drag-netting, are also destroying reefs. Coral bleaching was known over a century ago, but seems to have begun in earnest in the 1980s, and is attacking reefs in most parts of the world. In the early 1980's, 70 percent of the coral along the Pacific Central American coast bleached. It is estimated that 70 percent of coral in the Indian Ocean have died. The U.S. Coral Reef Alliance has estimated that 80 percent of coral near the Seychelles, and 90 percent near Indonesia have died. Corals offshore the Maldives, Bahrain, Sri Lanka, Singapore and Tanzania are deteriorated, and Caribbean coral is coming under pressure. Extensive coral reef structures near Jamaica, in the Caribbean, have lost their polyps and are now limestone skeletons covered with algae. Even when they survive, it is not easy for coral reefs to regenerate themselves. Estimates of reef growth range from one to 16 feet every thousand years. Healthy coral reefs foster species diversity. Funguses, sponges, mollusks, oysters, clams, crabs, shrimps, sea urchins, turtles, and many fish seek food and shelter amid reefs. The architecture of corals provides reef fish protection from carnivorous species such as sharks and barracudas. Sea cucumbers, worms, and mollusks burrow into the reef-generated sand to hide from their enemies. According to the Worldwatch Institute publication, "State of the World 2000," reefs include only 0.3 percent of the ocean area, but "one out of every four ocean species thus far identified is a reef-dweller, including at least 65 percent of marine fish species." Historically, coral reefs have been important to fishermen; increasingly, they stimulate local economies by drawing tourism. They protect coastlines from erosion, and over the eons have helped create brilliant beaches as their calcium carbonate leached on to the shore. According to the U.S. Fish and Wildlife Service, "Reef systems are storehouses of immense biological wealth" that provide "sources of food, pharmaceuticals, jobs, and revenues?. Reef habitats provide humans with services worth about $375 billion [thousand million] each year, despite the fact that they cover less than one percent of the earth's surface." The U.S. State Department estimates that "reefs provide one-quarter of the fish catch in developing countries and employment for millions of fishers." Corals are also sensitive indicators of the health of the aquatic environment. They flourish in a fairly narrow range of temperatures, salinity, and water purity. The die-off of corals going on in many oceans does not bode well for the health of the oceans themselves; and healthy oceans are essential if life on the planet is to be sustained in its current form. Attempts to restore coral reefs and manage their biological richness better include efforts being carried out to inventory and protect the structures themselves. Watershed management, including protection and conservation of wetlands with their mud flats, mangrove forests, and sea grasses, can help the estuarine system, including corals, to remain clean and healthy. Coral reefs have come to the attention of the public only recently, perhaps because fewer people visit a coral reef than a forest or prairie. Governments and privatesector organizations have taken note of the deterioration of the world's reefs, and are trying to find solutions. In 1994, the U. S. government helped found the International Coral Reef Initiative, a partnership designed to address threats to coral reefs. In 1996, the U.S. Coral Reef Initiative was launched to support these efforts and aid them domestically. And in 1998, the president issued an executive order directing U.S. government agencies to protect coral reefs. This executive order also established the United States Coral Reef Task Force, co-chaired by the Secretary of the Interior and the Secretary of Commerce, including other federal departments. Its duties include the promotion of reef mapping, scientific research, restoration, and collaboration with other nations. As it begins to operate, the task force has focused in on illegal trade in corals and associated sea life as one important cause of reef destruction. Even aquaculture of species such as shrimp can harm reef environments, in part by undermining biodiversity to produce large amounts of a single species. Efforts are under way in the U.S. Congress to support the task force and improve mapping and conservation of reef systems under U.S. jurisdiction. One way to help restore reef environments is simply to protect them from undue exploitation. Writing in Issues in Science and Technology, marine biologist Tundi Agardy observed, "Scientific studies on the effect of no-take reserves in East Africa, Australia, Jamaica, the Lesser Antilles, New Zealand, the Philippines, and elsewhere all suggest that small, strictly protected no-take areas result in increased fish production." In addition: "Preliminary evidence from a 1997 fishing ban in 23 small coral reef reserves by the Florida Keys Marine Sanctuary, indicates that several important species, including spiny lobsters and groupers, are already beginning to rebound." Australia's Great Barrier Reef Marine Park is often cited as one example of enlightened coral reef management. Nations as diverse as Guinea Bissau, Spain, and Croatia have established marine and watershed reserves. In many instances, national governments initiate the conservation measures; in others, local communities initiate conservation efforts, with the assistance of the government. Like all ecosystems, reefs have sections and areas more crucial to biodiversity than others. Determining which these are can be an important part of conservation. "Zoned" networks of vital areas of reef can be easier to protect than an entire system. When the most biologically vital parts of the reef are put off-limits, other areas can be made available for commercial use and tourism. The Florida Keys National Marine Sanctuary management plan, for example, establishes protective zones, as well as recreational and commercial zones -- and sets aside areas for scientific research. University of Maryland zoologist Marjorie L. Reaka-Kudla has estimated the number of species living on coral reefs at 950,000, of which about 10 percent have been studied and described. Mankind is just beginning to perceive the value of coral reefs, with their known supplies of food and as-yet-unexplored biota that could lead to the development of new medicines. The U.S. State Department estimates "half the potential pharmaceuticals being explored are from the oceans, many from coral reef ecosystems." In Reef Research, Dr. Patrick Colin, a marine "bioprospector," clearly described the hopes that had led him to spend the 1990s collecting marine samples in the Pacific for the U.S. National Cancer Institute (NCI). "Over the past 20 some years the NCI has been screening terrestrial plants and marine organisms worldwide for bioactivity against cancer and AIDS, and has come up with a number of hot prospects, a number of which are in clinical trials?. We try to collect from all environments possible, from shoreline areas with mangroves, beaches or rocks to deep offshore reef environments?. We do not collect any hard (stony) corals, threatened, endangered or locally protected species. We are mostly interested in soft-bodied sessile invertebrates which rely on their chemistry, rather than stinging cells, spines, jaws or teeth for their survival." Clearly, conservation of coral, and oceans in general, is linked to human survival and will continue to be an urgent issue in the 21st century. FORESTS: OUR PLANET'S ENDANGERED EDENS Forests are prime reservoirs of biodiversity, as well as the ancient cradle of the human race. Anthropologists believe that species ancestral to ours lived amid the trees, later emerging to grassland savannas to explore and hunt. Still cradles of life, forests also perform all kinds of practical services that benefit modern humans. They produce oxygen we breathe and suck up air pollution. In the United States, 80 percent of fresh water originates in forested areas. Forests purify water and refill underground aquifers; in addition, they absorb rain, and slow down floods and water runoff. Forests and woodlands over the world have changed over the millennia due to changes in climate and geology. In the modern world, forests are classified into various groups, including temperate-zone and tropical forests. Not all rain forests are in the tropics -- some are in cooler climates. And there are other kinds, such as riparian forests, that separate interior areas from coastlines. Each part of the forest supports life. The soil is full of uncounted numbers of microbes, insects, and fungi, essential to recycling organic matter, and thus to the survival of all life on earth. Larger animals live on the forest floor, and the shrub and tree canopy layers are vital to birds. There are about 1.5 million known species in the world, and the true number of species may be ten times more than that. Many of these spend their lives growing, burrowing, wriggling, or plodding along in forests -or flying through trees. The extent of forested lands has made it possible for birds and animals to range freely in search of food and appropriate climate; the resulting horizontal and vertical complexity of the forest and its density of life creates biodiversity. Tropical forests generate the richest biodiversity, as the energy generated by the equatorial sun encourages life to proliferate amid abundant nutrients. Unfortunately, these forests are quite fragile, and over the past half-century have succumbed in large numbers to human clearing and logging. Global forests themselves, as well as their diverse reserves of plants and animals, are threatened as never before. It has been estimated that by the late 1980s three quarters of old-growth forests on the planet had been destroyed, including about half of tropical and temperate rain forests; and human population expansion continues to lead to the clearing of new lands. According to the U.S. State Department, "one of every six known bird species, one of every 11 mammals, and one of every 15 reptiles" makes the Amazon rainforest its home. Unfortunately, as David B. Sandalow, assistant secretary of state for oceans and international environmental and scientific affairs, recently noted: "Tropical forests are disappearing at an alarming rate. Saws and bulldozers are leveling roughly 200 hectares per minute. A soccer field is close to two hectares, so we are losing about 120 soccer fields of tropical forest per minute, more than 7,000 soccer fields per hour, more than 170,000 soccer fields per day." Around the globe, forests that are not totally destroyed are being fragmented by roads and human development, a change that threatens the health and survival of the indigenous plants and animals. Biologists believe that destroying 90 percent of a wooded habitat reduces local species by about half. Harvard University biologist Edward O. Wilson has noted that "the poorest people with the fastest-growing populations live next to the richest deposits of biological diversity" and that a single "farmer clearing rain forest to feed his family?will cut more kinds of trees than are native to all of Europe." As the configuration of forests changes, other factors come into play as well. For instance, some forest dwellers require "edge" habitat, areas of woods near glades or grassland, to thrive, while others require the forest interior. Highly fragmented woodland areas diminish the proportion of interior to edge habitat and alter the balance of species. Greater exposure of once-sheltered trees to "edges" may cause them to dry out and become prey to invaders. Global climate change is liable to pose new challenges to the survival of forest ecosystems; habitat fragmentation could hinder the ability of species to adapt. Once a forest habitat has been weakened, it is more susceptible to disease and to alien species invasion. For instance, following World War II, most songbirds on the Pacific island of Guam were wiped out by a single species of snake, not native to the island. In the United States, some native birds have declined due to the thinning out of forests, which has made it easier for cowbirds to penetrate into woods and parasitize their nests. Many factors affect species decline. When a local population, or a subspecies, becomes diminished, its members breed with one another, amplifying genetic weaknesses and quite possibly precipitating a final decline to extinction. Effective forest conservation requires a commitment to look beyond the short term and to retain large forest areas for the bounty they can provide future generations. The greater the biodiversity of an environment, the greater its ability to withstand environmental stress and produce new and useful forms of life. Properly managed, forest animals and plants may produce more valuable medicine, food, and construction material over the years and decades than can be procured by clearcutting forests and destroying them in their current form. One frequently cited example of the rewards of maintaining biodiversity for future generations is the recent discovery of the Madagascar rosy periwinkle, which was found to produce chemicals that can cure Hodgkin's disease and childhood leukemia. About 3 percent of the world's flowering plants, so far, have been examined for anticancer chemicals similar to those of the periwinkle. In the United States, 25 percent of pharmaceutical prescriptions are derived from plant extracts and another 13 percent are from microorganisms. The venerable neem tree of South Asia has been thought for centuries to have all kinds of health-giving effects; yet, scientists are just beginning to study it systematically. Little-known plants and animals can be potent sources of pharmaceuticals because they have evolved a range of chemical strategies over the millennia to defend themselves from predators, survive, and thrive. Forests are stores of food. About a dozen fruits - apples, peaches, strawberries, bananas, etc. - dominate world consumption. There are probably about 3,000 more kinds of fruits in the tropics, of which 200 are widely eaten. Tens of thousands of other grains, vegetables, and forms of plant food are out there waiting to cure starvation and create greater variety on the dinner table, if they are allowed to survive. The winged bean of New Guinea, for instance, is full of protein, is entirely edible, and can be fried, roasted, ground into flour, or served as a hot beverage. And it grows to a length of 4 meters in a few weeks. The Amazonian babassu palm, still found in a natural state, offers the world's highest yield of vegetable oil from its fruit. It can also feed livestock, produce thatching materials, and be burned for charcoal. Iguana meat is prized by many in the Southern Hemisphere. Scientists estimate forest-ranched iguanas can yield ten times the amount of meat as cattle on the same acreage of cleared land. Other less well-known, yet tasty, animals could produce much food without destroying their forest cover. Much loss of forest cover, including loss of ancient forests, is due to harvesting for paper, at the rate of hundreds of millions of metric tons per year. There are less environmentally destructive ways to produce paper, including recycling, or the use of crops such as kenaf. Once an acre of forest is cut down and the trees sold for timber, its value of the land is often diminished. Some studies have shown that harvesting fruits, chocolate, substances such as latex, and vegetables can create more sustainable yield for a tropical farmer than a one-time timber harvest. One approach currently being used around the world is to identify biodiversity "hot spots" and to concentrate on saving those areas first. In a tropical forest, areas with the most diverse species of trees also tend to harbor the most diverse groups of shrubs, plants, birds, insects, amphibians, fish, and other creatures. Hotspots are not all in forests: they can vary in terms of geography and habitat and in the kinds of organisms they shelter. However, they are useful in delineating and protecting biodiversity. In 1997, one conservation group estimated that the 17 most vibrant hot spots in the world occupied 1.3 percent of the planet's land, yet protected 25 percent of terrestrial vertebrate species and 40 percent of plants. Clearly, well-maintained hot spots can begin to salvage the biological richness and potential of many nations, while mitigating the destruction of remaining wild areas. The Internet may become a tool in the service of forest conservation, posting and correlating the best data on deforestation and making it available worldwide. Global Forest Watch, an arm of the World Resources Institute, is attempting to create an international data and mapping network to track the pace of the destruction. Similar efforts may be made by other groups. The world is beginning to wake up to the need to save forests. Governments are increasingly committed to forest conservation. In 1992 at the Rio Earth Summit, nations adopted the Forest Principles, the first-ever global consensus on the importance of forest conservation. In 1995, the United Nations established the Intergovernmental Panel on Forests. David Sandalow adds, "Illegal logging may be the single greatest threat to tropical forests," and commends some nations for having "made major commitments to address the problems." The United States is implementing its own Tropical Forest Conservation Act. In March, 2000, the United States committed itself to a debt-for-nature swap with Bangladesh, to help conserve Bangladeshi tropical forests. Shortly thereafter, the U.S. government added 262,400 hectares of giant sequoia trees in California to its extensive network of national parks and nature reserves. Corporations are beginning to see the value of sustainable use of forests. Home Depot, a major U.S. retailer, has announced it will stop selling wood products from environmentally sensitive areas. The American Forest and Paper Association has committed itself to a focus on sustainable forest management. In 1997, the government of Bolivia, the Nature Conservancy, a U.S.-based not-forprofit organization, and American Electric Power provided funds and worked together to expand and protect an ecologically rich national park. The same year, a publicprivate partnership worked together to protect 4 million acres of rainforest in Suriname. In general, such partnerships involving many stakeholders, targeted to local conditions, seem to work the best. Agronomists are striving to continue to improve agricultural productivity, in order to make it less necessary to cut down forests for cropland. Around the world, 500 million people are thought to depend on forests for their livelihood - an incentive to preserve the health of forests and to protect them as a sustainable resource for future generations. WETLANDS: CRADLE OF SPECIES DIVERSITY Wetlands -- marshy areas of land where the soil is saturated with water -- are crucial incubators of species diversity, as important as tropical rain forests and coral reefs. They exist on all continents, save Antarctica, and include salty coastal flats, such as estuaries, and inland systems. Scientists classify wetlands into bogs, swamps, marshes, and other types, depending on geography, soil, and plant life. Wetlands help filter pollutants and soil runoff from upstream sources, which helps keep rivers, bays, and oceans downstream clean. In this way, healthy wetlands help mitigate the negative effects that human and farm waste, and some byproducts of industrial pollution, have on our Nation's water. Wetlands help control inland flooding and forestall wave erosion along shorelines; they diminish drought damage. Coastal wetlands protect spawning and feeding grounds for valuable fish and shellfish. Mink, otter, and other mammal species thrive in North American wetlands, as do myriad plants and insects, amphibians, and reptiles. They are vital nesting grounds for birds. According to the U.S. Environmental Protection Agency (EPA), wetlands are essential to the survival of about a third of the endangered animal and plant species in the United States, and about half of these species make use of wetlands at some point in their life. Unfortunately, especially in this century, the utility of wetlands has been poorly understood. They have been regarded as useless, or worse -- seen solely as breeding grounds for mosquitoes, other insects, or as sources of odors. Vast numbers of wetlands have been drained or destroyed to accommodate agriculture, dams, and human habitation. It's estimated that over half of the wetlands in the continental United States have been lost since the 18th century; and wetlands elsewhere have fared no better. With the destruction of wetlands has come destruction of biodiversity, both in the wetland areas themselves and downstream. For instance, nitrogen fertilizer runoff from farms has overwhelmed the capacity of some wetlands to filter pollutants, creating "dead zones" in areas such as the Gulf of Mexico, where algae blooms fueled by this and other nutrients have run riot and displaced a once thrivingly diverse ocean ecology. Wetlands in a sense are a biodiversity laboratory. For one, the diversity of conditions in wetlands set the environmental parameters that allow for, even encourage, the evolution of novel survival strategies. According to the EPA, for example, many bog species have "special adaptations to low nutrient levels, waterlogged conditions, acidic waters, and extreme temperatures." Vernal pools, ponds in winter and mud flats in summer, often include rare species that weather the drought as seeds, eggs, and cysts, and then grow into mature form when the ground is watery again. Mangrove swamps are full of shrubs and trees that have adapted to salty water. Wetlands are important to natural cycles involving water, nitrogen, and sulfur. Their plants and rich soil may provide one buffer against global climate change, by storing carbon instead of releasing it into the atmosphere as carbon dioxide. In dollar terms, the services wetlands provide are invaluable. According to the EPA, the Congaree Bottomland Hardwood Swamp in South Carolina performs water purification functions equivalent to a five million dollar wastewater treatment plant. Wetlands act like giant sponges, storing, then slowly releasing ground water, melted snow, and floodwater. Because urban buildings and pavements release water runoff quickly, wetlands downstream from urban areas perform valuable flood control services. In some cases, wetlands have been destroyed to create artificial flood control. Hardwood wetlands along the Mississippi river once stored 60 days' worth of floodwater. Now, due to filling or draining, they store 12 days' worth. Attitudes are changing. In the 1970's, the U.S. Army Corps of Engineers determined that draining 8,500 acres of wetlands near Boston would result in $17 million of flood damage per year - as a result, those wetlands were never drained. Even the finest wetlands, however, will ultimately be degraded or destroyed if too much pollution, silt, and non-native species are sent their way from upstream. Many familiar animals -- ducks, falcons, bears, deer -- make use of wetlands. Some species of migratory fowl are completely dependent on wetlands. Most commercial fish breed and nurture their young in coastal marshes and estuaries. Such familiar species as striped bass, shrimp, oysters, clams, and crabs can't survive without wetlands. Consequently, wetlands are essential sources of food for burgeoning human populations. Other wetland harvests include blueberries, cranberries, wild rice, and timber, not to mention plants that are sources of medicine. On the Southeastern shore of the United States, almost all commercial fishing depends on healthy estuary wetlands. In 1991, commercial fish and shellfish taken from the state of Louisiana's coastal marshes contributed $244 million to that state's economy. Fur-bearing animals -- muskrat, beaver, and mink -- add millions more. Wetlands are popular with hunters, fishermen, and tourists: nearby towns enjoy economic benefits as a result. In the United States, the Wetlands provision (1987) of the Clean Water Act established a "no net loss" policy for managing wetlands. In theory, this means that filled-in wetland areas should be offset with restored wetland acreage. In practice, this portion of the law has been slow to be implemented due to the differing interests of communities, environmentalists, and property owners. In addition, the government has offered tax deductions to people who donate or sell wetlands for conservation purposes, and has taken other measures to try to preserve them. Watershed conservation programs that include federal, state, local, and indigenous tribal governments have proved to be useful in managing streams, rivers, and wetlands. It's difficult to conserve and restore wetlands; the short-term interests of landowners and farmers frequently clash with the long-term benefits of a sustainable natural ecosystem. In the United States, there is particular concern about wetland areas of the Mississippi River, the Missouri River, and the Everglades swamp in Florida. Large parts of these riverine systems have been re-engineered, dammed, and channeled. Previous to this century, 150 species of fish are thought to have cavorted in the lower Mississippi River; now there are 90. Four-fifths of the 8.8 million hectares of wetland forest near the river were cleared. The Lower Mississippi River Conservation Committee is hoping to restore 50 percent of filled-in secondary channels, restore 32,000 hectares of drained wetlands, and reforest 52,000 hectares of wooded wetlands, as a start. In 1986, the U.S. Congress created the Missouri River Fish and Wildlife Mitigation Project. Over the years, the U.S. Army Corps of Engineers has used funds for this project to buy land from residents and use it to restore natural floodplain habitat. Governments at all levels are becoming involved in wetlands restoration. The city of Cleveland, Ohio, is planning to spend millions to restore wetlands in the region to compensate for an airport expansion that will destroy a watery area. According to the Associated Press, in Bath, Michigan, "a run-down, garbage-strewn park has been restored as a wetland, home to native Michigan wildlife?." In the New Orleans area, efforts are under way to restore wetlands, using aerial photographs from the 1930s and '40s to figure out where the wetlands were before they were destroyed. As part of a major effort to restore the Florida Everglades, Florida government officials and scientists are planning to construct five artificial wetlands on 17,200 hectares of land. In July, 2000, according to the Washington Post, "the Senate Environment and Public Works Committee reported out?a bill authorizing the first 10 of 68 planned projects meant not quite to restore the Everglades?that will never happen, but to revive and allow them to flourish once again." Plans are under way to acquire and restore about 10,000 hectares of wetlands in the Kankakee River Basin of northwest Indiana. The Grand Kankakee Marsh used to extend over 200,000 hectares. About 4 billion (thousand million) dollars has been spent cleaning up Boston Harbor, and more is being done. Scientists are trying to come up with new answers, figuring out, for instance, how farmers could use computers to determine how to farm with the least amount of wetland-disrupting fertilizer. Efforts in many parts of the world also play a vital role in preserving natural wetlands. The Australasian Wader Studies Group in conjunction with Wetlands International has completed five years of surveying and shorebird counting activities in China during the migration season, a step towards developing information about the importance of inland wetlands in China to bird species. Tasek Bera, the largest natural freshwater body in Malaysia, has been designated a Wetland of International Importance under the Ramsar Convention, raising the profile of an important cradle of many species. Often, the best advocates for wetlands are groups of concerned citizens and scientists willing to do exploration and to inventory declining species, and educators able to train local groups of people to better manage wetlands. Governments are becoming more sensitive to the need to protect wetland areas. A variety of approaches to wetland conservation, undertaken in many parts of the world, are effective in reversing or forestalling damage and in preserving biodiversity. In the end, however, natural systems are so complex that they are difficult to restore, once highly polluted and degraded. In her book "The Work of Nature," ecologist Yvonne Baskin writes, "Certainly, restoration efforts to return previously damaged lands to ecological service should be encouraged?. There are millions [of] hectares of rangelands, forests, and marsh on every continent that might be returned to health and productivity if complex environments could be rebuilt as skillfully as they are being dismantled." She points out, though, that "it would be far less costly to preserve robust natural systems rather than count on being able to piece them back together after they've been torn apart." NORTHLANDS: FRAGILE ECOSYSTEMS Biodiversity is at its most luxuriant in tropical areas. Yet, the far northern regions of the globe, while not host to as many species as warm latitudes, nourish and protect an abundant web of living things. Arctic lands demonstrate the ability of life to thrive in the most extreme conditions, by means of ingenious adaptations to climate, light, and nutrition. The Arctic is another elegant example of a self-sustaining, complex -and endangered -- planetary ecosystem. Many species of plants and animals live in polar regions -- from minute algae and lichen on bare rocks and ice to spectacular polar bears and falcons. In addition, the Arctic regions provide food and shelter for many migrating bird species from other parts of the world for important parts of their life cycles. Some Arctic and sub-Arctic areas are rich in oil and minerals. Extracting these natural resources without proper concern for the ecology, conservationists fear, could pose more of a threat to current forms of Arctic life than the cold, snow, and ice. In addition, there is evidence that global warming may be affecting the Arctic climate, with unknown consequences for its fragile biological riches. The southern part of the Arctic, which lies between the far North and the temperate parts of the planet, is called the sub-Arctic and contains a boreal woodland (named after the Greek god of the north wind, Boreas). Stretching from northwest to eastern Canada, and on to northern Europe and Siberia, it contains larches, spruce, and other conifers. Where the circumpolar timberline comes to an end as it stretches north, the tundra begins -- tundra being a Finnish word for an open plain. Tundra is open and often saturated with water. While devoid of forests, it is covered with other vegetation. Many tree species that grow in boreal regions continue northwards into the tundra, and there, take the adaptive form of dwarf varieties or shrubs. Underneath the tundra lies permafrost -- a layer of soil that is permanently frozen at all times of year. This keeps moisture from draining out of tundra, so in the summer months, there are plenty of liquid-borne nutrients for life to thrive. To people living in temperate latitudes, the permafrost regions of the world may be best known for preserving the remains of large extinct animals, mammoths, and mastodons. Yet, their living communities fascinate biologists. Usually, tundra is covered by snow, but in the warm months, an estimated 250 species of moss, lichens, grasses, shrubs, herbs, and sedges resprout. As these plants come to life in the spring, geese, terns, and many other species of birds fly north to nest in dry tundra, thereby making efficient use of the planet's nutrients and open space. The tundra plants take advantage of their short growing season to proliferate, and for a period of time dot their barren environment with bright flowers. Herbivores such as caribou, musk ox, and reindeer feed on plant life; and carnivores, such as wolves, survive by hunting and killing the herbivores. Other tundra denizens include hares, bears, foxes, lemmings, and the ptarmigan, a kind of grouse whose feathered feet protect it from the cold ground. There is also the polar bear, which is considered primarily aquatic, along with seals and walruses. Beluga whales and narwhals swim off the tundra coastline; whitefish, trout, stickleback, char, pike, and salmon thrive in fresh water. Sub-Arctic fauna is even more biodiverse than Arctic fauna. Some tundra animals such as caribou, reindeer, and the majority of Arctic bird species head south in the fall, leaving the tundra ground to renew itself for the next season. Birds, in particular, migrate extremely long distances, even to South America or regions near the Antarctic. By heading to the North during the summer, migrant animals take advantage of summer light and the high yield of nutrition from plant matter in the short but productive growing season. Tundra plants survive by adapting to extreme conditions. In the Arctic summer, they tend to grow close to the ground in mats, in order to derive warmth from the soil, and to keep moist rather than exposing themselves to drying winds. In the winter, they are protected by the snow that covers them as they lie dormant. Any animal that inhabits tundra regions during the winter has to be similarly well protected. The musk ox, for example, grows two layers of fur. The willow ptarmigan has waterrepellant outer feathers over a layer of inner feathers. It has also learned to dive into snow banks to save itself from extreme cold. The "woolly bear," a kind of caterpillar, freezes solid in the winter, yet thaws out and comes alive in spring due to a kind of anti-freeze in its metabolism that prevents cell damage. Such ingenious adaptations might well one day lead to new understandings of human biology, and new ways to help humans survive. There is substantial evidence that the Arctic Ocean is warming, based on temperature recordings and observations of melting glaciers. Other environmental issues affecting the Arctic are damage to the tundra from machinery, interference with wildlife migration by construction such as oil pipelines and roads, oil spills, and the fundamental fact that under such extreme conditions nature is slow to repair itself. Arctic ecosystems are particularly threatened by a group of chemicals known as persistent organic pollutants (POPs). POPs are very stable pesticides, industrial chemicals, and byproducts that can be transported over long distances from sources in temperate regions to the Arctic, where they are more likely to deposit because of colder temperatures. POPs are particularly dangerous because they can accumulate to toxic levels in humans and animals. Some of these chemicals are known or are suspected to cause cancer, perturb development, and reduce fertility in Arctic wildlife. A new global treaty on POPs is expected to reduce their future impact. Conservation of Arctic regions is a major issue among ecologists, perhaps in part because the Arctic is one of the last untrammeled and unexploited regions of the world. The Svalbard Archipelago, administered by Norway, is another protected region. The Norwegian government, in a recent report, has determined that "in the event of a conflict between environmental targets and other interests, environmental considerations are to prevail" and calls for "the maintenance of the virtually untouched nature of the environment with respect to continuous areas of wilderness, flora [and] fauna." It also expresses caution about plans to construct a road on the fertile island of Spitsbergen, noting it could "have major landscape and aesthetic consequences" and that "the sparse vegetation and the permafrost make the terrain extremely vulnerable to physical damage." The Arctic Council, whose members are Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden, and the United States, as well as groups representing indigenous peoples, is attempting to study Northlands environment and work out parameters for habitat protection and conservation on an international scale, while there is still time to protect the Arctic from massive exploitation. It manages a "Program for the Conservation of Arctic Flora and Fauna" called CAFF, and a number of similar programs. The Nature Conservancy, a not-for-profit organization in the United States, has made an effort to identify biodiversity "hot spots" and conserve them, including some in the North. Kachemak Bay, Alaska, according to the conservancy, contains "a healthy estuary" producing "four to ten times more organic matter than a corn field of the same size." Inventoried species there include sea lions, wintering bald eagles, harbor seals, orca and humpback whales, and about 230 other species of wintering birds, as well as "moose, brown and black bears, wolverines, wolves, otters, and lynx, numerous species of crabs, clams and mussels" and "numerous fish species including all five Pacific salmon, halibut, rock fish and herring." The Pribilof Islands in the Bering Sea lie near where "currents?bring nutrient-rich waters to the surface" and foster "extraordinary biological wealth," according to the Nature Conservancy. The Pribilofs help protect "seven great whales?listed as endangered" and provide breeding grounds for over two million seabirds a year. The islands also host a population of fur seals that "travel as far as 7,000 miles to return to their breeding grounds on the Pribilofs." The Bering Sea is home to over 400 species of fish. Conservation groups are encouraging the U.S. and Russian governments to cooperate in studying the Bering Sea ecosystem and to manage it in a sustainable fashion. As one moves from the richness of tropical forests northward, biodiversity becomes less luxuriant, but does not become less of an issue. Even in the most barren and frigid Arctic deserts, life is found in the form of microscopic diatoms that cling to ice, and, south of the tree line, it is profuse. Northern seas abound with plankton and marine life. Forms of life compete to wrest nutrition out of the soggy tundra. An ecosystem never exists as a separate entity. The Arctic is intrinsically linked with other global habitats, in ways that are only partly understood.