Transcript Chapter 11
Chapter 11 Sustaining Biodiversity: The Species Approach Core Case Study: The Passenger Pigeon - Gone Forever Once the most numerous bird on earth. In 1858, Passenger Pigeon hunting became a big business. By 1900 they became extinct from overharvest and habitat loss. Figure 11-1 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. Global Extinction Some animals have become prematurely extinct because of human activities. Figure 11-2 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 Fig. 11-3, p. 224 SPECIES EXTINCTION Some species have characteristics that make them vulnerable to ecological and biological extinction. Figure 11-4 SPECIES EXTINCTION Percentage of various species types threatened with premature extinction from human activities. Figure 11-5 IMPORTANCE OF WILD SPECIES We should not cause the premature extinction of species because of the economic and ecological services they provide. Some believe that each wild species has an inherent right to exist. Some people distinguish between the survival rights among various types of species (plants vs. animals). 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 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 The Greatest Threat to the Biosphere! But one of the greatest threats to biodiversity comes from the introduction of non-native species INVASIVE SPECIES Invasive (implies that it’s introduction has been a problem) Introduced Alien Exotic Nonindigenous Non-native (often applied to species that are more benign) Figure 11-A INVASIVE SPECIES Many Kudzu vine was introduced in the southeastern U.S. to control erosion. It has taken over native species habitats. 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. Figure 11-A Kudzu Kudzu Kudzu was introduced from Asia multiple times. Initially as an ornamental for trellises Then as a potential fodder for livestock And then finally as a cover for roadsides (during the 1950’ and 1960’s as the US Eisenhower Interstate system was being built). Kudzu is a vine and has a deep taproot (several meters). The vine grows like crazy and will cover large expanses of bare soil (and everything else) within one growing season (it can grow several inches per day). Unfortunately the ground cover does nothing to prevent soil erosion- the vegetation rests on the ground but it doesn’t stabilize the soil. It only has one tap root. Roadsides covered with grass are more stable because the grasses have fibrous roots (a mesh of a root system rather than a single taproot). Because of its inability to stop soil erosion it was abandoned as a road cover. It was ignored for about a decade, but by the 1970’s kudzu grew out of control. Today it is extremely hard to manage. Because it has a deep taproot, if you mow it or cut it it comes right back. Certain herbicides will control it but you have to mix very concentrated solutions, which kills the native vegetation and pollutes the watershed. Herbicides are not feasible over the large range. Goats do a pretty good job at keeping it at bay. Repeated weeding by people will also significantly reduce kudzu populations but this is labor intensive and not practical over large areas. In its native Asia, Kudzu is used in many different ways, to make bred, wine, paper, baskets, etc. Now in the Southeast, there are kudzu festivals that attempt to convince the public to use the kudzu. The hypothesis is that if people find kudzu useful (to be used as food, to make wine, or to use the vines for baskets) they will start collecting it more, and this will help reduce kudzu expansion. Kudzu INVASIVE SPECIES Many invasive species have been introduced intentionally. Figure 11-11 INVASIVE SPECIES Many invasive species have been introduced unintentionally. Figure 11-11 Brown Tree Snake, Guam There is a lot of concern about this snake being introduced into Hawaii or introduced within the warmer environments of the US (e.g. Florida or Louisiana). San Salvador Island Australian Pine on San Salvador Island 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 San Salvador Island Australian Pine on San Salvador Island Characteristics of Invasive Species 1) 2) 3) 4) 5) 6) Introduced into similar environment Reproduce easily and quickly No/few natural predators More efficient than natives at competing for resources Abundance of prey Invaders are well-adapted to human activity. Aquatic Invasive Plants Purple Loosestrife = escaped ornamental that is spreading at a rate of 115,000 hectares per year. Aquatic Invasive Plants Alligator weed = similar to the purple loosestrife, alligator weed is spreading throughout Southeastern wetlands – forming monospecific stands that block out light and out-compete the native aquatics. Aquatic Invasive Plants Water Hyacinth = naturalized from the Orinoco, introduced within many aquatic environments in warmer climates. The introduction of Water Hyacinth in Lake Victoria is especially problematic. It is chocking the lake and killing off many of the fish. Application of Herbicides to control water hyacinth http://dbw.ca.gov/images/hyancith.jpg Aquatic Invasive Animals Zebra Muscle = introduced into the Great Lakes (GL) and St. Lawrence from ship ballast water. The second reading has a good review of the economic impact of zebra muscles. Aquatic Invasive Animals Lampreys = migrated into the GL during the construction of the Welland Canal (1921), source = http://www.greatlakes.net/envt/flora-fauna/invasive/lamprey.html. The lamprey prey on native fish. Aquatic Invasive Animals Nutria or nutria rat = Originally brought in from South America for their fur, but they escaped into the salt marshes of the Gulf Coast and Maryland. The nutria eat the salt marsh grasses and are significantly increasing loss of coastal wetlands. 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 Case Study: Rising Demand for Bushmeat in Africa Bushmeat hunting has caused the local extinction of many animals in West Africa. Can spread disease such as HIV/AIDS and ebola virus. Figure 11-17 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 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. 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 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).