1. Biologists estimate extinction rates in one of three levels. Local extinction occurs when a species in a specific area is lost but the species is still found in other places. Ecological extinction describes a species that is so small it cannot play out its ecological role where it is found. Biological extinction means that the species is gone from the earth. Scientists use measurement and models to estimate extinction rates: studying past records, identifying species-area relationships, examining lists of threatened species. Extinction rates are increasing because of human activities. Our growing population, degrading and eliminating biological environments and biological hot spots all contribute to growing extinction rates.
2. Biodiversity and species extinction are important because species provide enormous economic and ecological services we need to survive. In 100 years, mankind will destroy species that it would take five million years to rebuild. These species may provide genetic information, medicines, and information about natural processes we need to discover. These wild plants and animals are economic, recreational, and health resources.
3. Many human activities endanger wildlife, such as degradation/loss of habitat; capture of wild animals, which prevents their breeding; overfishing, oil spills, and exposure to pesticides; and extinction from nonnative species, which we introduce.
4. To prevent premature extinction of species, we must reduce threats from nonnative species; end illegal poaching and hunting; provide means for people to survive economically without killing native animals for food; maintain predator species, not destroy them; reduce greenhouse emissions and deforestation throughout the world; develop governmental policies to support biodiversity; and protect wild species in sanctuaries.
9-1 What role do humans play in the premature extinction of species?
CORE CASE STUDY : Passenger pigeons were once one of the most numerous bird species on earth.
Uncontrolled hunting and habitat loss led to their extinction by the year 1900. There have been five mass extinctions on earth, and it appears we are currently entering the sixth. Human activities, it is predicted, will lead to the premature extinction of one-fourth to one-half of plant and animal species.
A. Background extinction is an historic, continuous, low level of extinction.
B. Extinction rate is the percentage or number of species that go extinct each year.
C. Mass extinction is the loss of many species in a short period of time.
D. Local extinction occurs when a species disappears from one of many areas it once inhabited.
E. Ecological extinction: the number of individuals is so low that they cannot fulfill their ecological roles.
F. Biological extinction: a species has disappeared from the earth.
G. Human activities increase the pace of extinction.
1. Current rate is 100—1,000 times the background rate (0.01–.1% per year).
2. Extinction estimates are likely conservative.
a. Rates will likely increase with the growing human population.
b. Rates tend to be much higher in biodiversity hotspots.
c. Habitat fragmentation limits the potential for speciation to occur.
H. Species heading toward biological extinction are either endangered or threatened.
1. Endangered species are so few in number that the species could soon become extinct.
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2. Threatened/vulnerable: still abundant but likely to become endangered in the near future. a. The World Conservation Union has kept Red Lists that are the world standard for listing all threatened species throughout the world.
SCIENCE FOCUS : Estimating rates of extinction is problematic because extinction takes a long time, we are uncertain of how many species there are on earth, and we know little about the species that have been identified. There are several methods for estimating extinction rates, such as studying fossil records and rates of mutation, applying a species-area relationship to habitat destruction, and building mathematical models. Scientists acknowledge the shortcomings of estimates of extinction rates, but are certain that humans have caused an increase in the rate of extinction.
9-2 Why should we care about preventing premature species extinction?
A. Wild species have instrumental value.
1. Use values: Economic goods and services, ecotourism, and genetic information.
a. Medicinal properties are found in many plants and some animals.
b. Genetic information in species helps them adapt and produce new species. This information can be used to develop food and medicines for people. Wild species provide a bank of genetic information.
c. Recreational value is provided by plants and animals.
2. Non-use values: existence value and aesthetic value.
B. Ecological value: each species is a vital component to ecosystem function.
SCIENCE FOCUS : Poachers slaughter about 25,000 elephants per year for their ivory. Since 2007, scientists have used a DNA map of elephant populations to trace the origin of ivory sold on the black market. This helps them to identify regions where poaching is occurring so they can focus efforts on eliminating it.
C. Intrinsic or existence value: species have an inherent right to exist, regardless of their utility to humans.
1. Biophilia: belief that humans have an inherent genetic kinship with the natural world.
a. Many people have a preference for natural scenes over urban environments.
b. Some believe that certain organisms have more of a right to life than others.
2. Biophobia: Fear of certain forms of wildlife.
SCIENCE FOCUS : There are about 950 species of bats. They reproduce slowly and live in large colonies, which makes them vulnerable to extinction. Bats are important for controlling insect populations, pollinating crops, and distributing fruit and seeds. Currently one-fourth of bat species are listed as endangered or threatened.
9-3 How do humans accelerate species extinction?
There are several causes of depletion and premature extinction of wild plants and animals. The acronym
HIPPCO describes these causes.
A. The loss, degradation, and fragmentation of habitat are the greatest threat to a species.
1. Deforestation in tropical forests is the greatest species eliminator followed by loss of wetlands and plowing of grasslands.
2. Island species are especially vulnerable to extinction. Many are endemic.
3. Habitat islands are isolated and surrounded by other habitats.
4. Habitat fragmentation occurs when large contiguous habitats are divided into isolated patches. a. Certain species are more vulnerable to habitat fragmentation. These tend to be those that are rare, require a large range, or have low reproductive capacity.
SCIENCE FOCUS : Tropical forests are generally very diverse. As these forests are fragmented, there is growing concern over the loss of biodiversity. Research illustrates that within 100 meters of the edge of the fragment, up to 36 percent of the biomass of old-growth trees is lost in 10 – 17 years. This information can help scientists estimate how large a fragment must be to prevent the loss of biodiversity.
CASE STUDY
: About 70% of the world’s bird species are declining in number
, and about 12 % is threatened with extinction. The primary cause of decline is habitat loss and fragmentation. Birds are seen as indicator species, signaling environmental change in their habitats. Birds play a number of important economic and ecological roles. Their loss could trigger a cascade of extinctions.
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SCIENCE FOCUS : Three species of vulture in India and South Asia were driven nearly to extinction in a few years beginning in the 1990s. The cause was poisoning from a pharmaceutical given to the cows they often fed on. The ecological ramifications of this population decline led to an increase in rabies amongst humans. The loss of vultures led to a greater food supply for wild dogs, and an increase in the number of dogs carrying rabies. Conservation biologists believe that the fates of wildlife and humans are often interconnected.
B. After habitat loss, introduced species are the biggest cause of extinction.
1. The alien species can be introduced accidentally or deliberately.
2. Some of these species threaten and endanger native species. a. They have no natural predators, competitors, or pathogens in their new habitat. b. They can trigger ecological disruptions. c. There are an estimated 7,100 invasive species that have caused ecological or economic harm in the
U.S.
CASE STUDY : The Kudzu Vine was deliberately introduced in the 1930s to control erosion, but got out of hand. It is prolific and difficult to control, engulfing hillsides, gardens, and trees, among other things.
3.
Invasive species are often introduced accidentally.
a. Argentine ants aggressively attack native ant populations.
4. The best control is to prevent the nonnative species from being introduced.
C. Population growth, overconsumption, pollution, and climate change.
1. Overpopulation and excessive consumption of resources eliminate habitat.
2. Pollution from chemicals like pesticides can have unintended effects on species.
3. Human activities induce rapid climate changes, increasing extinction rates.
CASE STUDY : The populations of many vital pollinators are currently in decline. Honeybees, in particular, are important pollinators of commercially grown crops. Since the 1980s there has been a decline in bee populations, and in the last few years the situation has become more severe. Colony Collapse
Disorder describes the sharp declines in some species of bees and could lead to agricultural collapse in the regions where the pollinators are lost.
CASE STUDY : Polar bears are distributed in 19 populations across the polar arctic. They are dependent on the ice that expands every winter for their feeding behaviors. As the climate warms, their summer fasting period becomes longer. Also, ice shrinkage is forcing them to swim longer distances in search of food.
According to the IUCN, polar bears may decline by 35% by mid-century, and may be confined only to zoos by the end of the century. The IUCN now list s polar bears as a threatened species.
D. Poaching—illegal killing of protected species.
1. Some protected species are killed for their valuable parts or are sold live to collectors.
2. Earns smugglers $10 billion peryear.
3. Low-risk, because smugglers are rarely caught and punished.
4. The internet is the main tool in this trade, and education is the key to combating it.
E. Global legal and illegal trade in wild species for pets is a very profitable business.
1. More than 60 bird species, mostly parrots, are endangered or threatened because of the wild bird trade.
2. Amphibians, reptiles, mammals, and tropical fish are also being depleted because of pet trade.
3. Ex-poachers in Thailand are now making more money taking eco-tourists into the forest than they did by poaching hornbills. They also protect these birds from poachers.
4. Collecting exotic pets and plants (such as orchids and cacti) kill large numbers of them and endanger these species and others that depend on them.
F. Bushmeat supplies indigenous people with food and has been harvested sustainably, but as demand has gone up illegal hunting has skyrocketed.
1. There has been an eightfold increase in Africa’s population, increasing demand.
2. Logging roads allowed ranchers, miners, and settlers into areas once too remote/inaccessible.
3. These hunting practices have resulted in negative ecological impacts and have driven at least one species to extinction.
9-4 How can we protect wild species from premature extinction?
A. Treaties help protect endangered and threatened species, but enforcement is difficult and punishment inadequate.
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B. The 1975 Convention on International Trade in Endangered Species (CITES) protects 900 species from being commercially traded and restricts international trade for 29,000 species that may become threatened.
1. Enforcement is difficult and varies from country to country.
2. Many countries are not signatories and still trade in animals.
3. The Convention on Biological Diversity (CBD) binds governments to reverse the global decline in biological biodiversity. The United States has not ratified this treaty. There are no severe penalties or other enforcement mechanisms in place.
CASE STUDY : The Endangered Species Act of 1973 (ESA) identifies and legally protects endangered species in the U.S. and abroad.
1. Identification of endangered, threatened ocean species is made by the National Marine Fisheries
Service, and the U.S. Fish and Wildlife Service is responsible for identifying and listing all other endangered and threatened species. a. Biological facts form the basis of inclusion on the endangered list. b. Habitats of endangered species must be protected.
2. Efforts have been made to repeal/weaken the Endangered Species Act by: a. Some developers, timber companies, and other private landowners avoid government regulations and loss of economic value by managing land to reduce its use by endangered species. b. Habitat conservation plans (HCPs) are designed to reach a compromise between interests of private landowners and endangered/threatened species. c. The HCP allows destruction of some critical habitat or killing of a population if the developer or landowner takes steps to protect that species using a series of steps such as protecting critical nesting sites, setting aside part of the habitat as protected land, maintaining travel corridors, or moving the species to another suitable habitat.
3. Conservation biologists believe that the ESA should be strengthened and modified to correct deficiencies.
C. The sanctuary approach is being used to protect wild species.
1. 547 federal refuges protect wildlife but the habitats are deteriorating due to invasive species, pollutants, and little operational or maintenance funding.
2. More than three-fourths of the refuges are concentrated along major bird migration corridors.
3. About one-fifth of U.S. endangered and threatened species have habitats in the refuge system.
SCIENCE FOCUS : The Endangered Species Act is often criticized because only 37 species have been removed from it. Biologists claim that the ESA has not been a failure because species are only listed when they face serious danger of extinction, it takes years for a species to become endangered and a long time for them to recover as well, conditions for more than half the species are stable or improving, and the ESA operates on a small budget. Some recommended changes include a larger budget, more rapid development of recovery plans, and a provision calling for the immediate establishment of a core area of survival habitat.
D. Gene banks, botanical gardens, and farms can be used to raise threatened species and help protect species from extinction; but funding is inadequate.
E. The world’s 1600 Botanical Gardens and Arboreta contain almost one-third of the world’s known plant species, but only 3% of the world’s rare and threatened species.
F. Raising some threatened or endangered species on farms can take some of the pressure off them and perhaps offer some for commercial sale.
G. Zoos and aquariums can help protect some endangered animal species as well, but they are both notoriously underfunded.
1. Egg pulling collects wild eggs laid by endangered bird species and hatches them in zoos/research centers.
2. Captive breeding takes wild individuals into captivity for breeding with the commitment to reintroduce the offspring back into the wild.
3. Artificial insemination, use of surrogate mothers, use of incubators, and cross-fostering by a similar species are other ways to increase populations of rare species.
4. The ultimate goal is to reintroduce these species into the wild.
5. Reintroductions of endangered species to the wild fail because: a. There is not suitable habitat. b. Individuals bred in captivity are not able to survive in the wild. c. There is renewed overhunting/capture of the returned species.
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CASE STUDY : The California Condor was nearly extinct, with only 22 birds in the wild. The remaining birds were captured and bred in captivity. As of 2007, there were 135 birds in the wild. A major threat remains from lead used in ammunition. When the birds eat carcasses, lead poisoning can make them very weak.
H. Precautionary Principle: When substantial preliminary evidence indicates that an activity can harm human health or the environment, we should take precautionary measures to reduce or prevent such harm.
Large Lecture Courses:
Allow your students to explore the concept of edge effects. Either project a map of a conservation area in your region, or diagram a hypothetical one on the board. Be sure to include major contributors of edge effects, such as roads, developments, agricultural lands, etc. Invite the students to suggest ways these external factors may limit the effective size of the reserve. Focus on issues such as noise. Then question the students about what effects these might have in the reserve, especially for avian diversity. Focus on pets along the urban edge, pollutants from residential and agricultural uses, etc.
Smaller Lecture Courses:
Break the students into small groups. Allow them 5–10 minutes to brainstorm amongst themselves the ways in which biodiversity impacts their lives. Visit each group while they are working and encourage them to think about large processes, such as nutrient cycling and a properly functioning hydrologic cycle. Compile the lists on the board and initiate a discussion about the value of biodiversity. In light of these considerations, do humans have an obligation to protect and conserve biodiversity?
1. Describe the economic, medical, scientific, ecological, and aesthetic, recreational, and ethical significance of wild species. Define biophilia. Summarize your position toward protection of different species.
2. Describe the general process of extinction. Compare past extinctions to present extinctions. Start with E. O.
Wilson's estimates for habitat destruction and loss of biodiversity. Calculate a range of estimations of biodiversity loss based on high and low assumptions.
3. Distinguish among local extinction, ecological extinction, and biological extinction.
Distinguish between threatened and endangered species. List nine characteristics that make species extinction prone.
4. List three root causes of extinction of wildlife. List eight human activities that directly increase the wildlife extinction rate. Summarize the condition of the world's fisheries and the causes of those conditions.
5. Explain how bioinformatics is being used to help protect wild species.
6. State and briefly describe the most far-reaching international treaty to protect wildlife. List four strategies that have been used recently to weaken the Endangered Species Act. List three recommendations for strengthening the Endangered Species Act. State three guidelines that conservation biologists would use to determine
"priority species."
7. Assess the advantages and disadvantages of using wildlife refuges, gene banks, botanical gardens, and zoos to protect wildlife.
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8. Describe how wildlife populations can be managed by manipulating the successional stage of the habitat and by sport hunting. Evaluate whose interests are generally the most influential in determining wildlife management priorities.
9. Describe freshwater and marine fishery management and how it can be improved. Analyze the lessons to be learned from the decline of the whaling industry.
endangered species (p. 186)
HIPPCO (p. 193)
threatened ( vulnerable ) species (p. 186)
1. Significance of wildlife: medicines derived from plants and animals; commercial products from wildlife; aesthetic and recreational significance of wildlife; ecological significance of wildlife.
2. Endangered and threatened wildlife: tropical deforestation and species extinction; the international trade in endangered species and exotic pets; lead poisoning in waterfowl and the American bald eagle; Florida's alien species problem; the California condor; the Florida manatee; the blue whale; bats; rhinos; elephants.
3. Protecting wildlife: bioinformatics; gene banks; zoos and captive breeding programs; habitat management; artificial reef-building materials and methods.
4. Individuals: scientific estimation of wildlife populations and successional stages.
5. Groups: Ducks Unlimited; the National Wildlife Federation; the Audubon Society; Greenpeace; Earth First!
6. National: America's National Wildlife Refuge System.
7. Global: the World Wildlife Fund.
1. Should animals be used for medical research? As sources of organs for surgical implants in humans? As sources of food, fur, fat, oils, and other commercially valuable products?
2. Are extremist tactics by Greenpeace necessary or justifiable?
3. Should sport hunting be used as a wildlife management tool?
4. Should limits be placed on genetic engineering for economic, aesthetic, ecosystem services, or other purposes?
5. The Endangered Species Act: success or failure?
6. Should we privatize fishing rights in the United States?
7. Should we lift the international ban on whaling?
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1. Are there zoos, aquariums, botanical gardens, or arboretums in your locale operating programs designed to increase the populations of endangered species? If so, invite a spokesperson to explain one or more of these programs to your class.
2. Ask your students to bring to class and share paintings, sketches, poetry, songs, and other artistic creations depicting the beauty and wonders of wildlife.
3. Have a game warden address your class about management of populations of fish and animals that are hunted for sport.
4. Compile a list of the fish and wildlife species in your locale that have been officially designated as threatened or endangered. As a class project, find out what specific actions are being taken to assist these species.
5. As a class, examine and evaluate the goals of the World Conservation Strategy. Develop objectives that could help implement the goals that are agreed upon by the class.
6. If there are rangelands in your locale, try to schedule a class visit to examples of well- and poorly-managed grazing lands. Compare the quantity and quality of vegetation present.
7. If possible, visit projects restoring prairie lands to a more natural state. Investigate how local citizens are participating in these programs and how they are progressing.
1. Do you believe that humans have a duty to subdue wild nature to provide food and other basic needs for people and to provide jobs and income through increased economic growth?
2. Do you believe that every living species has a right to exist, or at least struggle to exist, simply because it exists?
3. Do you believe that we have an obligation to leave Earth for future generations of humans and other species in as good a shape as we found it, if not better? Did past generations do this for you?
Cane Toads: An Unnatural History (Documentary, 1988)
A documentary detailing the spread of Hawaiian sugar-cane toads through Australia in a botched effort to introduce them as counter pests.
Frontline: World, Mexico: The Business of Saving Trees (Documentary, 2008, Online )
A look at how the carbon credit system has been use to create jobs in Mexico. http://www.pbs.org/frontlineworld/rough/2008/03/mexico_the_busi.html
Nova—Evolution: Extinction!
Main website: http://www.pbs.org/wgbh/evolution/extinction/
Teachers Guide: http://www.pbs.org/wgbh/nova/teachers/programs/0000_evoextin.html
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IUCN Red List http://www.iucnredlist.org/
Red list of threatened species from around the globe.
Encyclopedia of Life http://www.eol.org/
An online reference for all species named and documented on earth.
The following are examples of the material that should be contained in possible student answers to the end of chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and detailed responses to the questions depending on an individual instructor’s stated expectations.
1.
List three ways you could apply Concept 9-3 to make your life more environmentally sustainable.
Students might initiate a more sustainable lifestyle by supporting sustainable development initiatives that limit habitat degradation, avoiding overexploitation of species by not supporting the illicit trade in protected species, and limiting their carbon footprint as well as their contribution to other environmental pollutants.
2.
What are three aspects of your lifestyle that directly or indirectly contribute to the premature extinction of some bird species? What are three things that you think should be done to reduce the premature extinction of birds?
Answers for the first part will vary. Unfortunately, as habitat destruction worldwide, especially in tropical areas, is tied to common commodities in the United States, such as beef and soybeans, consumption of the products amounts to an inadvertent effect on bird species. Several things could be done to reduce this loss of biodiversity, including limiting habitat loss on a global scale, introducing new legislation to deal with the pet trade, and introducing new legislation and international treaties to deal with the fishing industry, which inadvertently leads to the demise of many seabird species.
3.
Discuss your gut-level reaction to the following statement: “Eventually, all species become extinct. Thus, it does not really matter that the passenger pigeon (Core Case Study, p. 222) is extinct, and that the whooping crane and the world’s remaining tiger species are endangered mostly because of human activities.” Be honest about your reaction, and give arguments for your position.
The possibility exists that at some point in the future species that currently exist on the earth may become extinct. This is part of the evolutionary process and we have much evidence for this from fossil records.
However, a main concern today is that humans are accelerating some species toward extinction, or have already brought about their extinction at rates that far exceed the rate that occurs within the natural process.
We may be bringing about the extinction of species that otherwise, left to their own devices, may not become extinct in the short term. Who knows how long the passenger pigeon would have existed in the natural world if it had not been subject to human-induced effects that brought about its demise? The horseshoe crab has essentially remained unchanged for over 200 million years, long before humans inhabited the earth, but since around 1990 the number of horseshoe crabs has declined worldwide by around 50% due to the effect of humans, for example, using them for bait in certain fishing industries.
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4.
Do you accept the ethical position that each species has the inherent right to survive without human interference, regardless of whether it serves any useful purpose for humans? Explain. Would you extend this right to the Anopheles mosquito, which transmits malaria, to infectious bacteria, and to individual tigers that have killed people? Explain.
Yes, every species that does exist has a right to exist without human interference. Humans have let themselves become apart from nature and feel that they have the right to become the masters over it. As such, we look at species only as being beneficial or detrimental to humans. This right to exist should be extended to any creature, whether it be a disease-causing vector such as the mosquito, a virus or bacterium, or an animal that sometimes attacks and kills humans that have ventured into, or encroached upon, its natural habitat. There are only a few sample vials of smallpox left in the world. An ethical debate exists as to whether these vials should be destroyed. They have a right to exist like any other organism on earth. We have eradicated the disease but who are we to decide to consciously bring about an organisms total eradication?
5.
Wildlife ecologist and environmental philosopher Aldo Leopold wrote, “To keep every cog and wheel is the first precaution of intelligent tinkering.” Explain how this statement relates to the material in this chapter. Explain how protecting wild species and their habitats is an important way to protect the health and well-being of people.
Aldo Leopold was speaking of the interrelatedness of species and the functionality of an intact ecosystem.
Loss of biodiversity can have unforeseen effects, which may ultimately break down the functionality of ecosystems. Humans, as a species, are dependent upon the proper functioning of ecosystems. Should species loss disrupt important processes such as nutrient or water cycling, the implications for humanity could be drastic. Additionally, we have little knowledge of the genetic diversity of species or their medicinal properties, and these aspects could prove very important to humanity in the future.
6.
What would you do if: (a) your yard and house were invaded by fire ants, (b) you found bats flying around your yard at night, and (c) deer invaded your yard and ate your shrubs, flowers, and vegetables?
(a) Stay away from the fire ants! Maybe use pheromone traps or introduce their natural predator. Find out how they got into the area and prevent entry from reoccurring.
(b) Make bat houses and put them up around the area to encourage more bats to take up residence.
(c) Plant crab-apple trees to lure the deer away from the flowers and shrubs.
7.
Which of the following statements best describes your feelings toward wildlife: (a) As long as it stays in its space, wildlife is okay. (b) As long as I do not need its space, wildlife is okay. (c) I have the right to use wildlife habitat to meet my own needs. (d) When you have seen one redwood tree, elephant, or some other form of wildlife, you have seen them all, so lock up a few of each species in a zoo or wildlife park and do not worry about protecting the rest. (e) Wildlife should be protected. Reflect on what your answer reveals about your environmental worldview (p. 22).
(e) Wildlife should be protected. My view lies somewhere between the stewardship worldview and the environmental wisdom worldview. We can manage forests sustainably and produce products that have been made using best management practices, but we should not allow wild species to suffer any harmful effects of our actions.
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8.
Environmental groups in a heavily forested state want to restrict logging in some areas to save the habitat of an endangered squirrel. Timber company officials argue that the survival of one type of squirrel is not as important as the wellbeing of the many families who will be affected if the restriction causes the company to lay off hundreds of workers. If you had the power to decide this issue, what would you do and why? Can you come up with a compromise?
We need to focus on saving whole ecosystems and not just focus on one particular species. We need to educate everyone about all of the species that live in the wooded area and maybe use the location for ecological education. The area could be assessed to determine where the population of squirrels is the smallest and maybe allow some selective cutting in that region only.
9.
Congratulations! You are in charge of preventing the premature extinction of the world’s existing species from human activities. What would you do to accomplish this goal?
First, take measures to reduce population growth, as this is the root cause of many environmental problems.
Second, strictly enforce wildlife protection laws locally, nationally, and globally. Third, educate the public about the benefits of protecting species.
10.
List two questions that you would like to have answered as a result of reading this chapter.
Student answers will vary and provide a good starting point for class discussion.
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