Conservation biology means different things to different people. For the purposes of this course, conservation biology means “all of the topics that I have chosen to include in the course and none of those topics that I haven’t.” Seriously though, there are reasons I chose the topics I chose to include. To understand what they are, it may help to begin with a little history.
I don’t think I have to convince anyone in this room that the world we now live in is far different from the one that was here a few thousand years ago.
1 The reason for that difference is two-fold: the growth of human populations and the enormous resource demands we make on the planet.
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The enormous increase in human population . The world had fewer than 3 billion people in in when I was born.
2 It reached 6 billion people in 1999. As of Sunday, it was a little under 7.3 billion (http://www.census.gov/popclock.html; Figure 1) 3
More importantly, the rate at which the world population has been increasing is faster than exponential (Figure 2 (left)). Even if average per capita resource use remained constant, such a massive increase in population size can’t go on forever.
• That’s the bad news.
The good news is that rates of population growth appear to have slowed.
The best guess from the United Nation’s population program is that world population will reach a little over 9 billion by 2050 (Figure 2
(right)) and about 10 billion by the end of this century. That’s 3 billion more than we have now, 4 but at least it appears that the unsustainable growth in the number of human beings on the planet is slowing down. There’s a lot of uncertainty about exactly how many people there will be at the end of the century. Fred Pearce [6]
1 And it’s not just because 10,000 years ago we would have been having this lecture underneath a mile of ice.
2 No, I wasn’t born in the Dark Ages, just the 1950’s. OK. Maybe that was the dark ages.
3
Two years ago the world population stood at just over 7.1 billion.
4
And as many as the entire planet had when I was born.
c 2001–2015 Kent E. Holsinger

Figure 1: Estimate of the total population of the world at 12:57:55pm EDT, 30 August 2015.
Figure 2: Human population growth over the last million years (left) and projections through
2050 (right). Source: Roberts, L. 2011. 9 Billion?
Science 333:540-543.
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severely criticized the most recent U.N. projections, for example. Still, both the U.N.
population council and its critics agree that there will be a little more than 9 billion people in the world by 2050, and that’s a lot of people. The best estimates for future human population size come from Gerland et al. [3]. As you can see from Figure 3, while the best guess is that there will be nearly 11 billion people on the world in 2100, the 95% prediction interval goes from a low of about 9.5 billion to a high of more than
13 billion.
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The enormous resource demands we make on the planet . Our numbers alone would be enough to ensure a great impact, but we also use many of the planet’s resources. Peter Vitousek, Pam Matson, and Paul Ehrlich [9] estimated 25 years ago that human beings capture over 40% of global net primary productivity, meaning that we are responsible for consuming nearly half of the annual energy input into the world’s ecosystems. A more recent attempt to estimate the same quantity [7] emphasizes how little we know about our cumulative impact. Nonetheless, the authors estimate that humans appropriate at least 10% and possibly as much as 55% of terrestrial net photosynthetic production (TNPP). Their best estimate is that we appropriate about
32% of TNPP.
• But that’s only the impact we have on net primary production. I can’t do it, but it’s conceivable that someone smarter than I am 5 could imagine a scenario in which humans co-opt 75% or 80% of net primary production without a significant impact on other inhabitants of the earth. The reason I can’t imagine such a scenario is that we’re currently co-opting no more than 55% of net primary productivity 6 , and we’ve already had enormous impacts on species and ecosystems around the globe [10].
– 10-15% of the earth’s land surface is occupied by row-crop agriculture or by urbanindustrial areas, and another 6-8% has been converted to pastureland. Total affected: between 15 and 25%, 40-50% of land surface has been transformed or degraded.
– 22% of marine fisheries are overexploited or depleted, another 44% are at their limit of exploitation.
– Humans use about 50% of the runoff water that is fresh and reasoably accessible.
Human activities add at least as much fixed nitrogen to terrestrial ecosystems as all other sources combined.
5 And there are a lot of people smarter than I am.
6 And probably only a third or so.
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Figure 3: Projections of human population growth through the end of the 21st century from [3]. The dark blue shaded area is the 80% prediction interval, and the lighter blue shaded area is the 95% prediction interval.
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Figure 4: Current and projected rates of annual nitrogen fixation due to human activities [1]
– Human activities are now responsible for fixing as much nitrogen as all terrestrial nitrogen fixation by bacteria, and anthropogenic nitrogen fixation is projected to increase by more than 60% between now and 2050 (Figure 4).
All in all, 83% of the earth’s land surface has been directly influenced by human activities (Figure 5), and our impact is pervasive in densely populated areas like the northeastern
United States (Figure 6). Peter Kareiva and colleagues point out that “we have domesticated landscapes and ecosystems in ways that enhance our food supplies, reduce exposure to predators and natural dangers, and promote commerce” [5, p. 1866]
The Millenium Ecosystem Assessment [1] summarizes the four key findings of their study this way:
• Over the past 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fiber, and fuel. This has resulted in a substantial and largely irreversible loss in the diversity of life on Earth.
• The changes that have been made to ecosystems have contributed to substantial net gains in human well-being and economic development, but these gains have been
5

Figure 5: The human footprint index reflects human population density, land transformation, access, and electrical power infrastructure [8] achieved at growing costs in the form of the degradation of many ecosystem services, increased risks of nonlinear changes, and the exacerbation of poverty for some groups of people. These problems, unless addressed, will substantially diminish the benefits that future generations obtain from ecosystems.
• The degradation of ecosystem services could grow significantly worse during the first half of this century and is a barrier to achieving the Millennium Development Goals.
• The challenge of reversing the degradation of ecosystems while meeting increasing demands for their services can be partially met under some scenarios that the MA has considered, but these involve significant changes in policies, institutions, and practices that are not currently under way. Many options exist to conserve or enhance specific ecosystem services in ways that reduce negative trade-offs or that provide positive synergies with other ecosystem services.
The changes have been so enormous that almost 15 years ago Paul Crutzen proposed that we refer to the modern age as the Anthropocene [2], recognizing that humanity’s impact on earth’s systems will leave a geological imprint.
The International
Commission for Stratigraphy includes a Working Group on the Anthropocene within
6

Figure 6: The human footprint index clearly shows metropolitan areas in the northeastern
United States. In addition to Boston and New York, which are labeled, it’s easy to pick out
Providence, RI, Hartford, CT, Springfield, MA, Worcester, MA, and Portland, ME. If you know the freeways in the area, it’s not hard to pick out I-95, I-91, I-90, and others. (See http://sedac.ciesin.columbia.edu/wildareas/maps.jsp for more maps of the human footprint index.)
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its Subcommission on Quaternary Stratigraphy.
It’s purpose is “to examine the status, hierarchical level and definition of the Anthropocene as a potential new formal division of the Geological Time Scale” (from the “Outline of working group activities” at http://www.quaternary.stratigraphy.org.uk/workinggroups/ , accessed 26 August
2011).
The Economist even put the Anthropocene on its cover in May 2011 (Figure 7) to accompany a leader
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( http://www.economist.com/node/18741749 ) and a special feature
( http://www.economist.com/node/18744401 ).
In the United States, it is possible to recognize three different responses to these problems.
Groom et al. [4] refer to these responses as “ethics” because each is intended to provide guidance about how we should act and the choices we should make with regard to our interaction with nature. We’ll return to these ideas and discuss them more in the final few weeks of the semester when we talk about valuing biodiversity.
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The Romantic-Transcendental Conservation Ethic
From the mid-nineteenth century into the early 20th century century Ralph Waldo
Emerson, Henry David Thoreau, and John Muir waxed eloquent about the wonders of nature in a mystical, almost religious language. Their writings convinced many
Americans of the need to save wild places, regardless of whether those places provide any direct economic benefit. The Sierra Club, which was among the earliest of the formal conservation organizations, grew out of Muir’s efforts to protect Yosemite and other parts of the Sierra Nevada.
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The Resource Conservation Ethic
In the late nineteenth century Gifford Pinchot, Teddy Roosevelt, and others recognized that it was in our own best interest to protect at least some portions of the natural world. Their motivation for doing so, however, was that we derived important “natural resources” from the earth. Unlike the romantic-transcendentalist conservationists, who hoped to protect natural areas for their own sake, Pinchot and the utilitarians hoped to protect natural areas for what they could do for us.
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The Evolutionary-Ecological Land Ethic
The most eloquent exposition of this approach is, of course, in Aldo Leopold’s A Sand
County Almanac . It is, in many ways, a synthesis of the preceding two. It lacks,
7 The Economist calls the editorials that lead off each edition “leaders.”
8

Figure 7: The cover of the 26 May 2011 edition of The Economist .
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mostly, the quasi-religious overtones of Thoreau and Muir, and it lacks the strictly utilitarian approach of Pinchot. Fundamentally, the land ethic recognizes that we do derive benefits from nature, but the connectedness of ecological systems means that it is difficult, if not impossible, to identify only some components as useful.
The first rule of an intelligent tinkerer is to keep all of the pieces. Aldo
Leopold, The Round River
We’ll return to a more complete discussion of ethical issues in the last lectures of this course. For now I just want to point out that the first and third of these ethics are widely accepted within conservation circles, but only the second has been persuasive to those not already committed to conservation. As a result conservation efforts, especially those prior to about 1960, were predominantly either concerned with:
• Land conservation — setting aside parcels of land for protection and public enjoyment or for scientific research, e.g., the
Nature Conservancy
.
• Wildlife conservation — management of game animal populations to provide opportunities for hunting, fishing, and observation, e.g., the
Audubon Societies and the
National Wildlife Federation .
Interestingly, conservation efforts, at least until the early 1960’s, were almost entirely concerned with biological conservation, by which I mean they were focused on protecting plants and animals, the wild areas they need to survive, or both. In the 1950s and especially in the 1960s, these concerns broadened into more general concerns about pollution and population (Rachel Carson, Silent Spring ; Paul Ehrlich, The Population Bomb ). Still, academic biologists in departments of botany, zoology, or biology 8 were little involved in providing advice to resource managers charged with protecting endangered species or with managing parks and nature reserves. Resource managers were trained largely in departments of forestry, natural resources, and wildlife management — departments whose faculty often had little contact with colleagues doing basic research in ecology, evolutionary biology, and systematics.
9 ments began describing the need for a field of conservation biology that would take the basic principles of ecology, evolutionary biology, and systematics and apply them to the problem
8 There weren’t any ecology and evolutionary biology departments until the mid 1960s, so far as I am aware.
9 Aldo Leopold was appointed Professor of Game Management at the University of Wisconsin in 1933, the same year he published Game Management .
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that many of those in traditional biological fields regard as the founding document of the field.
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In the 35 years since Soul´ Society for Conservation Biology has been founded, programs in conservation biology have sprouted (often in departments of forestry and natural resources) around the country, and traditional biologists have shown increasing interest in the questions conservation biologists pose. The focus of the field has also broadened. Two broad strains can be recognized within it:
• Conserving endangered species — Demographic and genetic consequences of small population size, population viability analysis, biology of small popualtions, manipulative techniques that enhance survival probability and design of nature reserves for particular species.
• Conserving functional and structural aspects of important ecosystems — Diversity and stability of ecological communities, habitat fragmentation, landscape ecology, island biogeography, and restoration ecology
More recently, we’ve come to realize that the idea that there’s a “nature” out there separate from human influence is wrong. Increasingly, conservation biologists pay attention to the human context in which their work takes place. There are degrees of human influence, or domestication as Kareiva et al. [5] call it. The course roughly follows these themes.
• First 40% of course deals with the biology of small populations
• Middle 40% of the course deals with reserve design and with ecosystem and habitat conservation
These are often complementary but need not be
– Few species on Federal list of endangered species in Connecticut, but we have the largest tidal undisturbed tidal marsh habitats in the Northeast
– Clarkia tembloriensis subsp.
calientensis — Only three or four known populations, each with 100 or fewer individuals. The habitat? Completely unremarkable sand hills near Bakersfield, California that are otherwise uninteresting biologically.
10 It’s worth noting, however, that the journal Biological Conservation began publishing in 1968. Moreover, many biologists working in resource-oriented departments have regarded what they do as conservation biology since at least the 1930s. Aldo Leopold was a wildlife biologist.
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• Final 20% of the course deals with patterns and values associated with biodiversity
There are many topics relevant to the broader question of how humans relate to their environment that we won’t deal with at all:
• Pollution — air, water, groundwater, disposal of radioactive waste, pesticides, electromagnetic fields
• Resources — energy, forest products, petroleum products, climate change 11
• Population
• Politics — how to get policy recommendations implemented, how political constraints affect policy recommendations, although we will deal a little bit with the economics of biodiversity conservation 12
Ecologists, evolutionary biologists, and systematists often suspend judgement rather than reaching definitive conclusions.
• Is inbreeding depression due primarily to the expression of recessive deleterious alleles or to loss of heterozygosity?
• To what extent does competition structure ecological communities?
• What are phylogenetic constraints and to what extent do they determine the form of animals and plants?
We may have strong opinions about these, but we (usually) recognize that intelligent people can disagree with us. Our most common statement is “Much more work is needed to sort out this problem.” We seek the challenge of solving problems that are difficult, interesting, and controversial. We sometimes enjoy the debate almost as much as the discovery.
11 We will discuss how climate change affects conservation planning, but we won’t talk about cap and trade or target levels of CO
2 in the atmosphere.
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We will obviously deal with politics to a limited extent. It’s unavoidable when talking about conservation issues. Our focus, however, will be on the biological issues associated with conservation, not the political ones.
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• Ecology, evolutionary biology, and systematics — Identify problems of interest, then selects methods of investigation and the taxa in which to investigate them.
• Conservation biology — Problems are chosen for us, must select methods of response
(management) and identify what we need to know to select those methods.
Conservation biology is a crisis-oriented science.
• There’s a lot we as scientists would like to know about the demography of spotted owls.
We may feel uncomfortable making a recommendation because we know how much we don’t know, and we don’t want to make a suggestion only to be proven wrong.
• A decision must be made now about how much forest is necessary to prevent it’s extinction.
– We are always tempted to say: “We just don’t know enough now. We need to study the problem further.”
– It sometimes feels as if we are being asked to provide an answer when the data just don’t justify it, but
– Recommending that 10 years of additional demographic data on the northern spotted owl is necessary before any decision can be made is equivalent to deciding now that 10 years of current practices will not doom it to extinction. Deciding to recommend further study is a decision. It is a decision that if there is a problem, we can still correct it later.
– Type I versus Type II error. As basic biologists the “cost” associated with rejecting a null hypothesis that is true is greater than that associated with failing to accept an alternative hypothesis that is true. As conservation biologists, the
“cost” associated with failing to accept an alternative hypothesis, that there is a population decline for example, may be much greater.
– We cannot avoid decisions or giving advice. We can only make the best decision or give the best advice with the data that are currently available .
• The vast number of species facing extinction precludes us from gaining a detailed knowledge of more than a few of them.
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• Our understanding of natural ecosystems is so limited and the interactions among their components so complex that we can’t hope to fully understand them before we start to manage them.
• We’ll talk more explicitly about methods for dealing with these uncertaintites later in the course, but they will underlie much of our discussion throughout the semester.
I’m going to argue in this course that biologists have the most to offer to conservation programs when they are:
• Providing rough and ready guidlines for decisions made with little data.
• Identifying what data will be most useful for future decisions.
• Developing adaptive strategies that start out with the small amount of information already available and build on it in a way to increase the chances of success.
[1] Millenium Ecosystem Assessment.
Ecosystems and Human Well-being: Synthesis . Island
Press, Washington, DC, 2005.
[2] Paul J Crutzen. Geology of mankind.
Nature , 415(6867):23, January 2002.
Spoorenberg, Leontine Alkema, Bailey K Fosdick, Jennifer Chunn, Nevena Lalic,
Guiomar Bay, Thomas Buettner, Gerhard K Heilig, and John Wilmoth. World population stabilization unlikely this century.
Science , 346(6206):234–237, 2014.
[4] M Groom, G K Meffe, and C R Carroll.
Principles of Conservation Biology . Sinauer
Associates, Sunderland, MA, 3rd edition, 2005.
[5] Peter Kareiva, Sean Watts, Robert McDonald, and Tim Boucher. Domesticated Nature:
Shaping Landscapes and Ecosystems for Human Welfare.
Science , 316(5833):1866–1869,
2007.
[6] Fred Pearce. Dubious assumptions prime population bomb.
Nature , 473(7346):125, May
2011.
[7] S Rojstaczer, S M Sterling, and N J Moore. Human Appropriation of Photosynthesis
Products.
Science , 294(5551):2549–2552, 2001.
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[8] E W Sanderson, M Jaiteh, M A Levy, K H Redford, A V Wannebo, and G Woolmer.
The Human Footprint and the Last of the Wild.
BioScience , 52(10):891–904, 2002.
[9] P M Vitousek, Paul R Ehrlich, A H Ehrlich, and P A Matson. Human appropriation of the products of photosynthesis.
BioScience , 36:368–373, 1986.
[10] P M Vitousek, H A Mooney, J Lubchenco, and J M Melillo. Human domination of earth’s ecosystems.
Science , 277:494–499, 1997.
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