Transcript chapter11
Chapter 11 Sustaining Biodiversity: The Species Approach Chapter Overview Questions How do biologists estimate extinction rates, and how do human activities affect these rates? Why should we care about protecting wild species? Which human activities endanger wildlife? How can we help prevent premature extinction of species? What is reconciliation ecology, and how can it help prevent premature extinction of species? Animation: Humans Affect Biodiversity PLAY ANIMATION SPECIES EXTINCTION Species can become extinct: Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world. Ecologically: Occurs when so few members of a species are left they no longer play its ecological role. Globally (biologically): Species is no longer found on the earth. Endangered and Threatened Species: Ecological Smoke Alarms Endangered species: so few individual survivors that it could soon become extinct. Threatened species: still abundant in its natural range but is likely to become endangered in the near future. Figure 11-3 SPECIES EXTINCTION Some species have characteristics that make them vulnerable to ecological and biological extinction. Figure 11-4 SPECIES EXTINCTION Scientists use measurements and models to estimate extinction rates. The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world’s threatened species. There are now 41,415 species on the IUCN Red List (2008 data) and 16,306 of them are threatened with extinction, up from 16,118 last year. IUCN web page Figure 11-5 SPECIES EXTINCTION Percentage of various species types threatened with premature extinction from human activities. Figure 11-5 SPECIES EXTINCTION Scientists use models to estimate the risk of particular species becoming extinct or endangered. Figure 11-6 Why Should We Care About Biodiversity? Aesthetic pleasure Ecological: (environmental monitor, ecological balance – keystone species) Educational Historical or cultural Natural Services: (air and water purification, soil fertility, waste disposal,) Recreational Medicine Agriculture: (biological pest control, food source, commercial product – wood) Moral or ethics HABITAT LOSS, DEGRADATION, AND FRAGMENTATION Conservation biologists summarize the most important causes of premature extinction as “HIPPO”: Habitat destruction, degradation, and fragmentation Invasive species Population growth Pollution Overharvest Animation: Habitat Loss and Fragmentation PLAY ANIMATION HABITAT LOSS, DEGRADATION, AND FRAGMENTATION The greatest threat to a species is the loss, degradation, and fragmentation of where it lives. Figure 11-7 HABITAT LOSS, DEGRADATION, AND FRAGMENTATION Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest. Figure 11-8 Case Study: A Disturbing Message from the Birds The majority of the world’s bird species are found in South America. Threatened with habitat loss and invasive species. Figure 11-10 INVASIVE SPECIES Many Arundo removal in the Santa Clara River Watershed nonnative species provide us with food, medicine, and other benefits but a a few can wipe out native species, disrupt ecosystems, and cause large economic losses. Click for Aurndo report Figure 11-A Negative Impacts of Arundo • Reduction in the shading of surface water, resulting in increased water temperatures and decreased dissolved-oxygen content, which has a negative impact on native wildlife • Reduction in groundwater availability through rapid transpiration • Alterations in channel morphology by retaining sediments and constricting flows • Increased bank erosion due to the diversion of water around established stands • Displacement of riparian habitat through monopolization of soil moisture • Displacement of riparian habitat due to establishment dense monocultures of arundo • Reduction in the food supply (particularly insects) of riparian-dependent wildlife • Reduction of wildlife utilization of an infested area • Increased probability of wildfire occurrences, intensity, and area from increased fire fuel loads INVASIVE SPECIES Many invasive species have been introduced intentionally. Figure 11-11 INVASIVE SPECIES Many invasive species have been introduced unintentionally. Figure 11-11 Quagga and Zebra Mussels in California Quagga fact sheet INVASIVE SPECIES The Argentina fire ant was introduced to Mobile, Alabama in 1932 from South America. Most probably from ships. No natural predators. Figure 11-12 INVASIVE SPECIES Prevention is the best way to reduce threats from invasive species, because once they arrive it is almost impossible to slow their spread. Figure 11-13 Characteristics of Successful Invader Species • High reproductive rate, short generation time (r-selected species) • Pioneer species • Long lived Characteristics of Ecosystems Vulnerable to Invader Species • Climate similar to habitat of invader • Absence of predators on invading species • Early successional systems • High dispersal rate • Release growth-inhibiting chemicals into soil • Low diversity of native species • Absence of fire • Generalists • High genetic variability • Disturbed by human activities Fig. 11-13, p. 236 POPULATION GROWTH, POLLUTION, AND CLIMATE CHANGE Population growth, affluenza, and pollution have promoted the premature extinction of some species. Projected climate change threatens a number of species with premature extinction. Pollution Each Example of biomagnification of DDT in an aquatic food chain. year pesticides: Kill about 1/5th of the U.S. honeybee colonies. 67 million birds. 6 -14 million fish. Threaten 1/5th of the U.S.’s endangered and threatened species. Figure 11-15 OVEREXPLOITATION Some protected species are killed for their valuable parts or are sold live to collectors. Killing predators and pests that bother us or cause economic losses threatens some species with premature extinction. Legal and illegal trade in wildlife species used as pets or for decorative purposes threatens some species with extinction. OVEREXPLOITATION Rhinoceros are often killed for their horns and sold illegally on the black market for decorative and medicinal purposes. Figure 11-16 PROTECTING WILD SPECIES: LEGAL AND ECONOMIC APPROACHES International treaties have helped reduce the international trade of endangered and threatened species, but enforcement is difficult. One of the most powerful is the 1975 Convention on International Trade of Endangered Species (CITES). • Signed by 169 countries, lists 900 species that cannot be commercially traded. Case Study: The U.S. Endangered Species Act One of the world’s most far-reaching and controversial environmental laws is the 1973 U.S. Endangered Species Act (ESA). ESA forbids federal agencies (besides defense department) to carry out / fund projects that would jeopardize an endangered species. ESA makes it illegal for Americans to engage in commerce associated with or hunt / kill / collect endangered or threatened species. Case Study: The U.S. Endangered Species Act Biodiversity hotspots in relation to the largest concentrations of rare and potentially endangered species in the U.S. Figure 11-18 Top Six Hot Spots 1 Hawaii 2 San Francisco Bay area 3 Southern Appalachians 4 Death Valley 5 Southern California 6 Florida Panhandle Concentration of rare species Low Moderate High Fig. 11-18, p. 241 Endangered Species Because of scarcity of inspectors, probably no more than 1/10th of the illegal wildlife trade in the U.S. is discovered. Figure 11-19 Endangered Species Congress has amended the ESA to help landowners protect species on their land. Some believe that the ESA should be weakened or repealed while others believe it should be strengthened and modified to focus on protecting ecosystems. Many scientists believe that we should focus on protecting and sustaining biodiversity and ecosystem function as the best way to protect species. How Would You Vote? Should the Endangered Species Act be modified to protect and sustain the nation's overall biodiversity? a. No. Protecting entire habitats will only further interfere with the rights of landowners. b. Yes. Protecting endangered habitats is more efficient and effective than saving individual species. PROTECTING WILD SPECIES: THE SANCTUARY APPROACH The U.S. has set aside 544 federal refuges for wildlife, but many refuges are suffering from environmental degradation. Pelican Island was the nation’s first wildlife refuge. Figure 11-20 PROTECTING WILD SPECIES: THE SANCTUARY APPROACH Gene banks, botanical gardens and using farms to raise threatened species can help prevent extinction, but these options lack funding and storage space. Zoos and aquariums can help protect endangered animal species by preserving some individuals with the long-term goal of reintroduction, but suffer from lack of space and money. RECONCILIATION ECOLOGY Reconciliation ecology involves finding ways to share places we dominate with other species. Replacing monoculture grasses with native species. Maintaining habitats for insect eating bats can keep down unwanted insects. Reduction and elimination of pesticides to protect non-target organisms (such as vital insect pollinators). Using Reconciliation Ecology to Protect Bluebirds Putting up bluebird boxes with holes too small for (nonnative) competitors in areas where trees have been cut down have helped reestablish populations. Figure 11-B What Can You Do? Protecting Species • Do not buy furs, ivory products, and other materials made from endangered or threatened animal species. • Do not buy wood and paper products produced by cutting remaining oldgrowth forests in the tropics. • Do not buy birds, snakes, turtles, tropical fish, and other animals that are taken from the wild. • Do not buy orchids, cacti, and other plants that are taken from the wild. • Spread the word. Talk to your friends and relatives about this problem and what they can do about it. Fig. 11-21, p. 246