Transcript Chapter 12
Chapter 12 Extinctions Local- species is no longer found in an area it once inhabited Ecological- numbers of species are so few that it can no longer play its ecological roles in biological communities Biological- species is no longer found anywhere on Earth (forever) Endangered VS. Threatened Endangered- so few individual survivors that species could become extinct Threatened- abundant in natural range but declining numbers & likely to become endangered Characteristic Examples Low reproductive rate (K-strategist) Blue whale, giant panda, rhinoceros Specialized niche Blue whale, giant panda, Everglades kite Narrow distribution Many island species, elephant seal, desert pupfish Feeds at high trophic level Bengal tiger, bald eagle, grizzly bear Fixed migratory patterns Blue whale, whooping crane, sea turtles Rare Many island species, African violet, some orchids Commercially valuable Snow leopard, tiger, elephant, rhinoceros, rare plants and birds Large territories California condor, grizzly bear, Florida panther Vulnerable to extinction Extinction Rates 0.1 to 1% per year 1,000 to 10,000 times higher than prior to humans Rates Rate of species loss & the extent of biodiversity loss are likely to increase in next 50-100 years due to human population growth Current & projected extinction rates are much higher than global average in endangered centers of biodiversity Humans are eliminating degrading & simplifying many biologically diverse environments Why? It will take at least 5 million years for speciation to rebuild the biodiversity we are likely to destroy during this century. Intrinsic value- (existence) inherent right to exist & play its ecological role regardless of its usefulness to us Biophilia- love of life Habitat loss Overfishing Pollution Habitat degradation and fragmentation Climate change Commercial hunting and poaching Introducing nonnative species Predator and pest control Sale of exotic pets and decorative plants Secondary Causes •Population growth •Rising resource use •No environmental accounting •Poverty Basic Causes Causes of Reduction of populations Premature Extinctions Habitat disturbance – agriculture, commercial development, water development, outdoor recreation, livestock grazing, pollution Indian tiger, Black rhino, African & Asian/Indian elephant Habitat fragmentation - large, continuous area of habitat is reduced in area & divided into small scattered, isolated spots (Deliberate) Nonnative species- used as biological control; no natural predators, competitors, parasites, or pathogens to help controls numbers; wipe out native species, disrupt ecosystems & cause large economic losses Figure 12-9b Page 235 Sea lamprey (attached to lake trout) Argentina fire ant Brown tree snake Eurasian muffle Common pigeon (Rock dove) Formosan termite Zebra mussel Asian long-horned beetle Asian tiger mosquito Gypsy moth larvae Accidentally introduced Species (Accidental) Nonnative species- arrive as stowaways on aircraft, tankers, cargo ships; no natural predators allow rapid spreading Poaching- killed for valuable parts or sold to collectors; increases chances of premature extinction Mountain gorilla (live), panda pelt, chimpanzee, Imperial Amazon macaw, rhinoceros horn Figure 12-9a Page 235 Purple looselife European starling African honeybee (“Killer bee”) Marine toad Water hyacinth Japanese beetle Deliberately introduced Species Nutria Salt cedar (Tamarisk) Hydrilla European wild boar (Feral pig) Predator & pest control- people exterminate species that compete with them for food & game animals Elephants, prairie dogs, wolves, bobcats, coyotes Exotic & decorative- profitable Exotic birds (macaw), amphibians, reptiles, mammals, tropical fish Climate change & pollution- human activities bring a rapid climate change Polar habitats Pesticides- honey bees, birds, fish Birds Decline in population – 70% 1 in 6 bird species – threatened with extinction Environmental Condition Indicator 1. Live in every climate & biome 2. Respond quickly to environmental changes to habitats 3. Easy to track & count Characteristics of Successful Invader Species Characteristics of Ecosystems Vulnerable to Invader Species • High reproductive rate, short generation time (r-selected species) • Similar climate to habitat of invader • Pioneer species • Absence of predators on invading species • Long lived • High dispersal rate • Release growthinhibiting chemicals into soil • Generalists • High genetic variability • Early successional systems • Low diversity of native species • Absence of fire • Disturbed by human activities Figure 12-12 Page Reducing the Threat 1. Identify characteristics that allow species to become successful invaders & vulnerable ecosystems 2. Inspect imported goods that may contain invaders 3. Identify harmful invader species & pass laws banning transfer 4. Prevention & control CITES Convention on International Trade in Endangered Species Restrictions on species that cannot be traded or sold (over 30,000 species) Difficult to enforce Enforcement varies from country to country Highly profitable trade occurs in countries that did not sign treaty ESA Endangered Species Act Designed to identify & legally protect endangered species in US & abroad Americans cannot sell or buy products made from these animals HCPs Habitat Conservation Plans Landowners, developers, loggers allowed to destroy part of endangered or threatened species population on private land in exchange for taking steps to protect the species Safe Harbor Agreements Landowners voluntarily agree to take specified steps to restore, improve, or maintain habitat for threatened or endangered species located on their land Voluntary Candidate Conservation Agreements Landowners agree to take steps to help conserve a species whose population is declining ***All 3 are designed to be a compromise between private landowners & interest of endangered & threatened species Landowner Compensation Advantages- Disadvantages- cost, hinders passage of new land use, environmental, health, & safety laws ESA Expensive failure Only 37 species have been removed from this list 14 recovered 8 extinctions Others removed due to technical errors or discovery of new populations Wildlife Refuge Serve as a vital wetland sanctuary for migratory waterfowl Some set aside for specific endangered species Bad news- 60% of activities that are harmful to wildlife occur within refuges; invasions by nonnative species; too much hunting/fishing & use of powerboats & offroad vehicles cause damage Gene Bank Preserves genetic info & endangered plant species by storing seeds in refrigerated, low-humidity environment; store wide range of threatened species & genetic diversity Bad news- expensive to operate; destroyed by accidents; prevents evolution Botanical Gardens Arboretums Contain living plants; educates million of visitors Bad news- too little capacity; too little funding Zoos Used to preserve some individuals of critically endangered species with long-term goal of reintroducing the species into protected wild habitats Egg pulling- collecting wild eggs laid by critically endangered bird species & hatch in zoos or research centers Captive breeding- wild individuals are captured for breeding with aim of reintroducing offspring into the wild Bad news- lack of space & money; major role needs to be education Aquarium Exhibits unusual & attractive fish & marine animals; education to public about need for protection; not an effective gene bank Bad news- considered a prison; fosters the false notion that preserving small numbers is useful Reconciliation Ecology Science of inventing, establishing, & maintaining new habitats to conserve species diversity in places where people live, work, play Examples Butterfly habitat- 20+ neighbors provide self-sustaining habitat would attract birds or bat-eating insects Safe harbor agreements- bluebirds- nest boxes