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Transcript
Amphibian decline case study 1963, many breeding bright orange toads (Bufo periglenes) 1989, only a single male was observed Today, the toads have gone extinct Amphibians in trouble Frog populations that had once been abundant were now decreasing or entirely gone In 2005, evidence that 43% of amphibian species experienced decreases in population size 1/3rd are threatened with extinction Number of threatened species Why worry about amphibian declines? Many species have declined in pristine, well-protected habitats Particularly sensitive to the state of the environment because of their moist skin Chemicals pass into their body Larvae are aquatic, adults are terrestrial No single cause for amphibian decline is apparent Types of habitat destruction Destruction Pollution Disruption Fragmentation Rainforest in Madagascar 90% habitat loss 16 of 31 primate species threatened or extinct Extinction is related to area Habitat degradation Reduction in the quality of available habitat Pollution Bald eagle Disruption Fragmentation Neotropical migrants Disruption Four visits by visitors to bat cave per month caused 86% - 95% declines in population size Human activities can have ramifications throughout the food chain In Alaska, otter numbers have fallen 90% since the 1970s due to overharvesting of whales Deforestation and fragmentation in WI Fragmentation research Edge effects Ecological/biotic influences which occur within areas of “natural habitat” in close proximity to modified habitats Includes changes in microclimate, predation, invasion of exotics (particularly weedy species), and human disturbance Neotropical migrants Songbird decline Migrant songbirds have declined Nest in northern forests in summer but spend winter in South or Central America or the Caribbean Islands Caused by habitat fragmentation and loss in summer and wintering areas Overexploitation 37% of all endangered, vulnerable and rare species of vertebrates are threatened by overexploitation Fur-bearing animals (giant otter, most species of cats) Elephants (for ivory) All species of rhinoceros (for aphrodisiacs) Whaling “The Passenger Pigeon needs no protection. Wonderfully prolific, having the vast forests of the north as its breeding grounds, traveling hundreds of miles in search of food, it is here today, and else-where tomorrow, and no ordinary destruction can lessen them or be missed from the myriads that are yearly produced.” Committee report on the game bill to the State Legislature of Ohio, 1857 Bushmeat Invasive species Plants, animals and other organisms that establish themselves in new ecosystems and are able to reproduce, spread and persist to the detriment of the native environment Invasive species Invasive species threaten 19% of all endangered and vulnerable species Greatest impact on islands Impacts through predation, competition, and/or habitat modification Economic impacts of invasive species Cause economic damage - $140 Billion per year in United States Decreased yield and quality in agriculture, forestry and fishing Disrupts waterways and limits opportunities for boating and recreation Cost of prevention and control How do they get here? Humans have greatly increased colonization rates Intentional introduction - intended for use in agriculture, horticulture, medicine, or erosion control Accidental - stowaways in ballast on ships and as contaminants in imported materials Mongoose Released in Hawaii to control rats Rats are nocturnal and Mongooses are diurnal Both are now problems Asian tiger mosquitoes Arrived on container ships carrying used tires Spread West Nile Virus Hawaiian birds Effects may not be direct Argentine ant has spread through much of the southern US, reducing populations of native ant species Negative effect on coast horned lizard which feeds on native ants Native ants spread seeds, introduced ones do not Small populations Some species have been reduced to small numbers Small numbers of species are prone to extinction due to Demographic factors Genetic factors The interaction of these two factors Demographic factors Random event Skewed sex ratios Allee affect Factors Responsible Lack of genetic variability is a second dilemma small populations face Genetic drift Populations lacking variation composed of sickly, unfit or sterile individuals More genetically variable individuals have greater fitness Illinois prairie chicken Inbreeding depression in alleviated by managers adding new chickens to population Restoration ecology Restoration ecology seeks to repair or reconstruct ecosystems damaged by humans or natural forces Tools of restoration Horticultural or animal control methods Removal of invasive species Seed broadcasting Fire Let nature heal itself Captive breeding Breeding programs in zoos and botanical gardens are one method of saving threatened species Most mammals in North American zoos are now produced from captivebreeding programs Many zoos now participate in reintroduction programs Peregrine falcon Conservation of ecosystems Focus on preserving pristine state in national parks and reserves Amount of land preserved is limited Not many areas completely protected Also focus on surrounding areas with some level of human disturbance Management of ecosystems Operate them in a way compatible with local land use No economic activity in core pristine area Remainder of land used for nondestructive harvesting of resources Some hunting Corridors of dispersal Size and design of nature preserves For some species with small territories, several small isolated refuges can support viable populations But cannot support species requiring large amounts of space or edge sensitive species Corridors of natural habitat to allow movement of species from one area to another can help maintain genetic exchange in fragmented areas Corridors Link pristine areas Increase population sizes Allow recolonization due to catastrophe Protection to species that move over great distances during the course of a year Conservation of ecosystems