Biodiversity and Conservation Biology

Transcription

1 11 Biodiversity and Conservation Biology Chapter Objectives This chapter will help students: Characterize the scope of biodiversity on Earth Contrast the background extinction rate with periods of mass extinction Evaluate the primary causes of biodiversity loss Specify the benefits of biodiversity Assess the science and practice of conservation biology Analyze efforts to conserve threatened and endangered species Compare and contrast conservation efforts above the species level Lecture Outline I. Central Case: Saving the Siberian Tiger A. Up until the past 200 years, tigers roamed widely across the Asian continent, from Turkey to northeast Russia to Indonesia. B. Of the tigers that still survive in small pockets of their former range, those in the subspecies known as the Siberian tiger are the largest cats in the world. C. For thousands of years, the Siberian tiger coexisted with the native people of what is today the Russian Far East, who equated the tiger with royalty and viewed it as a guardian. D. The Russians who moved into and exerted control over the region in the early 20th century had no cultural traditions that expressed respect for the animal, causing the species to decline to as few as 20, perhaps 30, animals. E. International conservation groups began to get involved, working with Russian biologists to try to save the dwindling tiger population. 163

2 F. Today, the population is in a range of 430 to 500 tigers, and 1,500 more survive in zoos around the world. II. Our Planet of Life 1. Biological diversity, or biodiversity, is the sum total of all organisms in an area. a. Biodiversity takes into account the diversity of species, their genes, their populations, and their communities. A. Biodiversity encompasses multiple levels. 1. Species diversity is expressed as the number or variety of species in the world or in a particular region. a. A species is a distinct type of organism, a set of individuals that uniquely share certain characteristics and can breed with one another and produce fertile offspring. b. Speciation, the generation of new species, adds to species diversity, while extinction decreases species diversity. c. Taxonomists, the scientists who classify species, use an organism s physical appearance and genetic makeup to determine its species. d. Biodiversity exists below the species level in the form of subspecies, populations of a species that occur in different geographic areas and differ from one another in some characteristics. 2. Genetic diversity encompasses the differences in DNA composition among individuals within a given species. a. Genetic diversity provides the raw material for adaptation to local conditions. b. In the long term, populations with more genetic diversity may stand better chances of persisting, because their variation provides them more genetic options with which to cope with environmental change. c. Populations with little genetic diversity are vulnerable to environmental change, because they may happen to lack genetic variants that would help them adapt to novel conditions. 3. Ecosystem diversity, community diversity, habitat diversity, and landscape diversity are all ways to view biodiversity. B. Some groups hold more species than others. C. Measuring biodiversity is not easy. 1. Many species are tiny and easily overlooked. 164

3 2. Many organisms are so difficult to identify that ones thought to be identical sometimes turn out, once biologists look more closely, to be multiple species. 3. Some areas of Earth still have been hardly explored. D. Biodiversity is unevenly distributed. 1. The latitudinal gradient influences the species diversity of Earth s biomes. 2. For any given area, species diversity tends to increase with the diversity of habitats, because each habitat supports a somewhat different set of organisms. III. Biodiversity Loss and Species Extinction 1. Extinction occurs when the last member of a species dies and the species ceases to exist; in contrast, the extinction of a certain population from a given area, but not the entire species globally, is called extirpation. A. Extinction occurs naturally. 1. Most extinctions preceding the appearance of humans have occurred one by one, at a rate that paleontologists refer to as the background rate of extinction. B. Earth has experienced five mass extinction episodes. C. Humans are setting the sixth mass extinction in motion. D. Current extinction rates are much higher than normal. 1. To keep track of the current status of endangered species, the World Conservation Union (IUCN) maintains the Red List. E. Biodiversity loss involves more than extinction. F. Several major causes of biodiversity loss stand out: 1. Habitat loss 2. Invasive species 3. Pollution 4. Overharvesting 5. Climate change 6. Human Population IV. Benefits of Biodiversity A. Biodiversity provides ecosystem services free of charge. B. Biodiversity helps maintain ecosystem function. 165

4 C. Biodiversity enhances food security. D. Organisms provide drugs and medicines. E. Biodiversity generates economic benefits through tourism and recreation. F. People value and seek out connections with nature. 1. Edward O. Wilson has popularized the notion of biophilia, asserting that human beings have an instinctive love for nature and feel an emotional bond with other living things. G. Do we have ethical obligations toward other species? V. Conservation Biology: The Search for Solutions A. Conservation biology arose in response to biodiversity loss. 1. Conservation biology is a scientific discipline devoted to understanding the factors, forces, and processes that influence the loss, protection, and restoration of biological diversity. B. Conservation biologists work at multiple levels. C. Endangered species are a focus of conservation efforts. 1. The primary legislation for protecting biodiversity in the United States is the Endangered Species Act (ESA). Passed in 1973, the Endangered Species Act forbids the government and private citizens from taking actions that destroy endangered species or their habitats. D. Conservation efforts include international treaties. 1. The 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) protects endangered species by banning the international transport of their body parts. 2. In 1992, the leaders of many nations agreed to the Convention on Biological Diversity, a treaty outlining the importance of conserving biodiversity, using it sustainably, fairly distributing its benefits, and committing signatory nations to conserving this diversity. E. Captive breeding, reintroduction, and cloning are being used to save species. 1. Zoos and botanical gardens have become centers for the captive breeding of endangered species, so that large numbers of individuals can be raised and then reintroduced into the wild. 2. The newest idea for saving species from extinction is to create individuals through cloning. F. Forensics is being used to protect threatened species. 166

5 1. By analyzing DNA from organisms or their body parts sold at market, researchers can often determine the species or subspecies of organism, and sometimes its geographic origin. The analysis can help detect illegal activity and enforce the laws protecting wildlife. G. Some species act as umbrellas for protecting habitat and communities. H. Parks and protected areas help conserve biodiversity at the ecosystem level. I. Biodiversity hotspots pinpoint regions of high diversity. 1. Biodiversity hotspots are areas that support an especially great diversity of species, particularly species that are endemic to the area, or found nowhere else in the world. J. Innovative economic strategies are being employed. 1. One strategy is the debt-for-nature swap. In such a swap, a conservation organization raises money and offers to pay off a portion of a developing nation s international debt in exchange for a promise by the nation to set aside reserves, fund environmental education, and better manage protected areas. 2. A newer strategy that Conservation International has pioneered is the conservation concession. Developing nations often sell concessions to foreign multinational corporations, allowing them to extract resources from the nation s land. K. We can restore degraded ecosystems. L. Community-based conservation is growing. 1. In community-based conservation, biologists engage local people in efforts to protect land and wildlife. VI. Conclusion A. The erosion of biological diversity could bring on a mass extinction event equivalent to the major ones of the geological past. B. The primary causes of biodiversity loss include habitat alteration, invasive species, pollution, overharvesting, and global climate change. C. Many conservation biologists are rising to the challenge with traditional and innovative strategies to save endangered species and their habitats. Key Terms background rate of extinction biodiversity hotspots biological diversity (biodiversity) biophilia captive breeding 167

6 community-based conservation conservation biology Convention on Biological Diversity Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) ecological restoration ecosystem services Endangered Species Act (ESA) endemic extinction extirpation genetic diversity habitat fragmentation mass extinction Red List species species diversity Teaching Tips 1. Download the NatureServe 2002 report States of the Union: Ranking America s Biodiversity ( NatureServe ranks the 50 states and the District of Columbia based on diversity of species, levels of rarity and risk, endemism, and number of extinct species. Provide students with information about your state. Then ask them these questions: How does it rank? Is the state high or low in biodiversity? High or low in endemism? High or low in extinction rates? How does it compare to surrounding states? 2. Assign students to research a species that is listed with the current IUCN Red List of Threatened Species ( Information is accessible via the Red List database through a search by category, region, and/or country. Where does the species live? What threatens the species? What is the status of the species? What is being done to protect the species? Species on the Red List are placed in a category based on their status : Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Lower Risk, Near Threatened, and Data Deficient. A description of each category can be found on Ask students what they think the categories mean and then provide them with the official definition. 3. Download an overview of the Endangered Species Act published by the U.S. Fish and Wildlife Service ( This overview gives basic information about the ESA, including how species become listed, a timeline of major events, how the law is enforced, and how habitat conservation plans are implemented. Ask students to compare the Endangered Species Act with the Red List. 4. Assign students to conduct Internet research for updates on the Siberian tiger population. For example, they might uncover that in February 2003, a photograph was taken of a wild Siberian tiger in northeastern China, suggesting that the population is returning to areas it formerly populated ( 168

7 5. A consensogram is a tool that can be used in two ways: for surfacing student misconceptions and also for sharing opinions about a controversial topic. The instructor makes a large bar chart, either on a sheet of paper or on the board. A question is posted above the chart, and possible answers are displayed along the x axis. As students enter the room, have them come to the bar chart, read the question, place a small sticky piece of paper (or fill in a square on the bar chart) atop the bar for their answer choice, and sit down. When has all students have made their choices, there will be a bar graph, or histogram, showing the number of students who chose each answer. If the question is commonly misunderstood, such as, Where does the material for the increase in biomass of a growing plant come from? (Possible answers: sunlight, water, soil, carbon dioxide in the air, oxygen in the air), then this is an excellent departure point for a lecture on plant growth and photosynthesis. If the question asks for opinions about a topic, such as the preferred method for attempting to preserve a particular endangered species (or not), then it can serve as a good beginning for a class discussion as well. Additional Resources Websites 1. Conservation International ( Conservation International s website describes its conservation regions, strategies, and programs. 2. Convention on Biological Diversity, United Nations Environment Programme ( This UN website provides information about the Convention on Biological Diversity, an international treaty to conserve the world s biodiversity. The full text of the treaty and international case studies can be accessed. 3. Invasivespecies.gov, National Agricultural Library for the National Invasive Species Council ( This online resource gives information about federal efforts concerning invasive species. The website also describes the impacts of invasive species and presents species profiles. 4. National Biological Information Infrastructure (NBII), U.S. Geological Survey ( This website provides access to images, data, and information about the nation s biodiversity. 5. Publications of the IUCN The World Conservation Union ( 169

8 This website, and its publications, discuss and provide information about the efforts of the SSC to protect species worldwide. 6. The Nature Conservancy ( This listing provides information about The Nature Conservancy s programs and success stories around the world. 7. Island Press ( Extensive resources for text and AV resources on the science of restoration ecology. 8. Society for Ecological Restoration International is a professional organization for individuals involved in landscape-scale restoration. This international organization shares information and resources with the global community on projects ranging from wetland restoration in southern Iraq to restoring fragile arctic tundra post oil rig platform removal. ( Audiovisual Materials 1. Before It s Too Late, 1993, Storyteller Productions video, distributed by The Video Project ( This video investigates the efforts of scientists worldwide to save endangered species and preserve global biodiversity. 2. Natural Connections (Classroom Version), 2000, Howard Rosen Productions video, distributed by Bullfrog Films ( This video is divided into five programs: Introduction to Biodiversity; The Significance of Salmon; Keystone Species; Forests, Biodiversity and You; and Biodiversity vs. Extinction. 3. Wild Places, Scientific American Frontiers, PBS Home Video ( This episode of Scientific American Frontiers looks at the current extinction crisis and innovative conservation strategies implemented around the world. 4. Conserving Earth s Biodiversity, E. O. Wilson and Dan Perlman, distributed by Island Press ( This CD-ROM program features video clips of E.O. Wilson, interactive exercises, case studies, and maps to introduce the topic of biodiversity and its current crisis. Weighing the Issues: Facts to Consider Bioprospecting in Costa Rica Facts to consider: Much of this question requires a personal response. Some responses may indicate that this agreement is at least a starting point a partial 170

9 model, showing that there are constructive alternatives to bioprospecting that benefit companies in developed nations but not the countries of origin. The agreement does allow for a small royalty to INBio and the Costa Rican government if a product is developed based on the original agreement; however, these royalties transpire only if a product goes to market. Though both sides did get some benefit in this agreement, many might argue that it would be more equitable if greater benefits to the contracting company also led to greater benefits to the developing country. A case study about the issue can be found in the Trade and Environment Database (TED) of The American University ( Biophilia and Nature-Deficit Disorder Facts to consider: Most of this question requires a personal response. To answer the last part of the question, students may discuss how a survey might help determine whether most people in a community have an affinity for other living things, asking questions about recreation, values, and charitable preferences. So, too, might a tally of how many households have pets, how well pet-supply businesses are doing, activity levels in local parks, or participation in outdoor recreational activities. Using a more interactive, applied approach, a day in front of a local grocery store promoting animal adoptions with a local animal shelter might yield interesting, even quantifiable, results. Single-Species Conservation Facts to consider: Answers will vary depending on background and experience. One advantage of single-species conservation is in highlighting public awareness. A single species provides a visible symbol for supporters to showcase in making pleas for contributions. It is easier to show the plight of an organism with statistics and photos rather than that of an ecosystem, especially if the organism in question is charismatic megafauna, such as a lion, tiger, or bear. Facilities for restoring populations can be built anywhere, and with advances in veterinary medicine and expertise in exotic animal husbandry, most organisms respond quite well to captive breeding programs. Finally, it is simpler to collect data to show the progress of population restoration in captivity and in the wild. There are, however, some disadvantages to single-species conservation. If a species is removed from the wild because the initial population is too small, reintroduction of the organism to the wild poses very serious problems both to the organism and to the ecosystem. With California condors, for example, the chicks were mostly raised by hand, and so workers had to train condors how to behave like condors and to avoid humans, sometimes using extreme methods. From a genetic standpoint, the species is weakened because of the small size of the gene pool. If the species is to be reintroduced into the wild, other obstacles can arise. If the habitat is not appropriate to the organism or not protected from direct or indirect human-induced damage, all of the time, effort, and funding put into saving the species will be lost 171

10 as the organism dies out. A single species is reliant on the abiotic conditions and biotic communities with which it evolved, and so any alteration of these conditions will select against the species being reintroduced. The conservation of charismatic megafauna has exacerbated this as the only organisms deemed worth saving are typically large mammals or birds, not the less charismatic vertebrates, invertebrates, or plants. Finally, preserving and conserving habitats protects species that have yet to be discovered, described, and studied, and may be more economically feasible in the long term. The Science behind the Stories: Thinking Like a Scientist Amphibian Diversity and Decline Observation: The rate of discovery of new amphibian species is tremendous. Question: Does Sri Lanka have more than the 40 species of frogs already known to live on the island? Study: In the 1990s, Madhava Meegaskumbura and his team spent eight years collecting frogs from 300 study sites and compared a variety of their physical, behavioral, and genetic traits to the same traits of previously identified Sri Lankan frog species. Results: More than 100 new species of amphibians were found. Observation: At the same time that the Meegaskumbura team showed the scientific community that there were still many amphibian species yet to be discovered, populations of many other amphibians were decreasing at alarming rates, some with no apparent cause for the decline. Researchers main concern was that amphibians were being affected by a combination of harmful environmental conditions. Question: What may have caused such drastic decreases in amphibian populations? Hypothesis: Because all amphibians breathe and absorb water through their skin at some stage of their life, they are sensitive and vulnerable to individual or a combination of external environmental stressors. Experiment: Rick Relyea and Nathan Mills conducted an experiment that exposed young frogs tadpoles to two environmental stressors: predators and pesticides. These researchers had three groups of tadpoles: tadpoles exposed only to pesticides, tadpoles exposed only to predators, and tadpoles exposed to both pesticides and predators. Joseph Kiesecker conducted a similar experiment, exposing frogs to pathogens and pesticides. Results: The experiments yielded similar results. Combinations of environmental stresses have the greatest influence on the death rate of the frogs tested. In Relyea 172

11 and Mills s study, tadpoles exposed to low levels of pesticide and the presence of predators had a 25% lower survival rate than if only the pesticide was present. In Kiesecker s study, frogs were more susceptible to parasitic infections if also exposed to pesticides in water. While these studies do not define a specific cause for amphibian population decline, the research does point to combinations of environmental conditions having the most influence over amphibian survivorship. Using Forensics to Uncover Illegal Whaling Observation: Conservation biologists long suspected that much of the whale meat on the market was actually caught illegally for the purpose of selling for food, and that fleets from nations such as Japan were killing more whales than international law allowed. Question: Is all whale meat sold in Japan caught legally? Hypothesis: Illegal samples would be found on grocery store shelves in Japan, labeled generically as whale meat. Experiment: Baker and Palumbi bought samples of whale meat all labeled simply as kujira, the generic Japanese term for whale meat from a number of markets in Japan. They sequenced DNA from these samples. Results: It was concluded that they had sampled meat from 9 minke whales, 4 fin whales, 1 humpback whale, and 2 dolphins. One fin whale came from the Atlantic whereas the other 3 were from the Pacific, and 8 of the 9 minke whales came from the Southern Hemisphere. Because several of these species and/or subspecies were off-limits to hunting, the data suggested that some of the meat had been hunted, processed, or traded illegally. Observation: Two years later, Baker, Palumbi, and Cipriano presented results from markets in South Korea and Japan. Again their genetic sleuthing revealed a diversity of whale species, and they stated that their data were difficult to reconcile with records of legal catches (scientific whaling by Japan and fishing bycatch by South Korea) reported by these nations to the IWC. Among the whales they detected were two specimens of what seemed to be a subspecies or species of whale new to science. Question: Was illegal fishing continuing, and was this illegal catch still being sold on grocery shelves? Hypothesis: Illegal harvest of meat was continuing in South Korea and Japan. Experiment: In 2000, the team analyzed 655 samples from Japanese and South Korean markets. Results: Evidence was found of 12 species or subspecies of whales, along with orcas, porpoises, and dolphins and even sheep and horses! Seven of the whale species were internationally protected, and together these constituted 10% of the whale meat for sale in Japanese markets. In 2007, Baker led a team that combined genetic forensics with ecological methods to estimate numbers of individual whales 173

12 whose meat was passing through Korean markets. They inferred that meat from 827 minke whales had passed through South Korea s market in five years. The nation had reported catching only 458 minke whales as fishing bycatch, leading the researchers to conclude that the remainder had been taken illegally. Answers to End-of-Chapter Questions Testing Your Comprehension 1. Biodiversity has no single definition. At the species level, it refers to both the number of different species present in an area and to the evenness or relative abundance of those species. At the genetic level, it refers to the genetic variety within a single species. At the ecosystem level, it refers to the number and variety of ecosystems in an area. The concept may be applied at the community, habitat, and landscape levels as well. 2. Habitat alteration, invasive species, pollution, overexploitation, and climate change are all causes of biodiversity loss. Examples, in the order of the factors just mentioned, are hydroelectric dams altering stream habitat, zebra mussels in the Great Lakes, air pollution killing forest trees, Siberian tigers being hunted to near extinction, and climate change affecting the cloudforest fauna in Monteverde. 3. The zebra mussel (a small, striped mollusk), has spread rapidly through eastern North American waterways, fouling ship motors, pumps, docks, and so on. Feral pigs in Hawaii alter the habitat for mosquitoes, increasing the invasive mosquito species Culex quinquefasciatus, which spreads avian malaria and avian pox diseases among the native bird populations. Humans are an invasive species, too. We ve transported many agricultural species, as well as many weeds, some of which have naturalized in their new habitats, thus altering the local ecological balance. 4. Processes provided by ecosystems, such as air and water purification, are called ecosystem services. Other than those just mentioned, ecosystems also: provide food, fuel, and fiber; detoxify and decompose waste; and stabilize and moderate Earth s climate. 5. Biodiversity increases food security by providing the genetic diversity for species to adapt to a wide range of growth conditions, and by providing potential new species for cultivation. Salt-tolerant plants that produce animal feed, vegetable oil, and wood may increase the food supply and prosperity of the world s poor living in areas with saline soils, for instance. Many pharmaceuticals are derived from wild species, and many more are awaiting discovery. Australia has an active research program to survey its unique biota for useful pharmaceuticals, and has found the compounds hycoscine, salsodine, and prostaglandin E2, among others. 174

13 6. Biodiversity provides valuable ecosystem services free of charge. It helps maintain ecosystem function, provides natural classrooms, enhances food security, provides economic benefits through tourism and recreation, and provides traditional medicine and high-tech pharmaceuticals. 7. The U.S. Endangered Species Act (ESA) has resulted in the rebounding populations of the peregrine falcon, brown pelican, and bald eagle, all of which have been removed from the endangered species list. Fully 40% of species with declining populations have been stabilized. The ESA has been criticized for valuing endangered species above the livelihood of humans, and because of fears that it will unreasonably restrict the use of private land. 8. Captive breeding can offer controlled conditions such as protected habitats, lack of natural predators, and a steady supply of food. This could benefit many populations. For example, in 1982, the population of the California condor, North America s largest bird, had dwindled to only 22 animals in the wild, but rebounded in 2010 to 176 in captivity and 180 in the wild after the help of a captive breeding program. At this point, maintaining a species by cloning is not a viable alternative, as without ample habitat and protection in the wild, having cloned animals in a zoo does little good. 9. An umbrella species requires large areas of habitat. If sufficient habitat is protected to preserve that umbrella species, many other species with smaller habitat requirements will also benefit. A keystone species is one that plays a crucial role in the trophic web of an ecosystem. Since keystone species are often top predators that require a large area of habitat, they can be both keystone and umbrella species. 10. In a debt-for-nature swap, a conservation organization raises money and offers to pay off a portion of a developing nation s international debt in exchange for a promise by the nation to set aside reserves, fund environmental education, and better manage protected areas. In a conservation concession, developing nations often sell concessions to foreign multinational corporations, allowing them to extract resources from the nation s land. Calculating Ecological Footprints Hectares of forest used for Total forest hectares used housing You Your class Answers will vary Answers will vary Your state Answers will vary Answers will vary United States 120,000, ,000,

14 1. The majority of the remainder of forest product use is wood pulp for the production of paper and packaging materials. 2. If a forest is harvested at greater than its sustainable rate, the result will be a decrease in the standing stock of forest materials. This will eventually result in deforestation. For communities in the area, this will likely mean a loss of jobs in the local timber industry and a loss of jobs in other sectors that depend on the forest, including ecotourism. Erosion and pollution may increase, and quality of life and land and housing values may decrease. 3. If the plots are large enough to fragment the forest, then species that depend on intact forest habitat will decline or disappear. If the plots are small, then species that thrive in gaps in the forest may increase, and local species richness may even increase. (b) Clear-cutting will completely change the array of organisms present in an area, killing or driving out all forest-dependent species, and providing habitat for a considerably smaller array of species that can thrive in clear-cuts. (c) Simplification of a forest into a plantation monoculture of equalaged trees greatly reduces the diversity of niches available, and thereby reduces the species diversity of the forest community considerably. Spatial scale makes a difference in all of these instances, for example, for part (a). Moreover, the greater the scale over which forest loss or habitat occurs, the more likely species are to be lost from entire regions. 176