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Human Disturbances to Ecosystems Sustaining Biodiversity

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  • Human Disturbancesto EcosystemsSustaining Biodiversity

  • The Passenger Pigeon: Gone ForeverOnce the most numerous bird on earth.In 1858, Passenger Pigeon hunting became a big business.By 1900 they became extinct from over-harvest and habitat loss.

  • I. Endangered and Threatened Species: Ecological Smoke Alarms

    A. Endangered species: so few individual survivors that it could soon become extinct.B. Threatened species: still abundant in its natural range but is likely to become endangered in the near future.

  • II. Species ExtinctionA. Species can become extinct:

    1. Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world.

    2. Ecologically: Occurs when so few members of a species are left they no longer play its ecological role.

    3. Globally (biologically): Species is no longer found on the earth.

  • 3. Globally (biologically): continued.

    Some species have become permanently extinct because of human activities.

  • II. Species ExtinctionSome species have characteristics that make them vulnerable to ecological and biological extinction.

  • II. Species Extinction1. The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the worlds threatened species. 2. The IUCN takes the following into account:Population Size & Reduction of it

    # of Mature Individuals

    Geographic Range of Population

    Quality of Habitat

    Probability of Extinction

    B. Scientists use measurements and models to estimate extinction rates.

  • The border of Haiti and the Dominican Republic

  • II. Species ExtinctionC. Causes: Conservation biologists summarize the most important causes of premature extinction as HIPPO: 1. Habitat destruction, degradation, and fragmentation 2. Invasive Species 3. Population growth 4. Pollution 5. Overharvest

  • H. Habitat lossBiggest threat to biodiversityWhen area to live is gone, organisms die

    Why would the habitats go away?

    Ex. deforestation

  • Habitat FragmentationSeparation of wilderness areas from other wilderness areasFragmented areas are like islands; the smaller the fragment, the less biodiversity it will support

  • Figure 55.5 Fragmentation of a forest ecosystem

  • Habitat destruction, degradation, and fragmentationReduction in ranges of four wildlife species, mostly due to habitat loss and overharvest.

  • Biotic and Abiotic Issues of FragmentationBiotic:-some organisms need large areas to gather foodEx. LionsEx. Zebra

    -no migratory routes to re-establish populations lost due to natural disasters

    Abiotic:-climate can change

    -can cause EDGE EFFECT(different conditions along the boundaries of an ecosystem)

  • I. Introduction of Exotic (invasive) SpeciesNew orgs introduced into an ecosystem; do not have any natural predators and is little competition with other orgs, so native species are at riskExotics may take over niches of native species and eventually replace the native species completely

  • Invasive SpeciesMany nonnative species provide us with food, medicine, and other benefits but a few can wipe out native species, disrupt ecosystems, and cause large economic losses.Kudzu vine was introduced in the southeastern U.S. to control erosion. It has taken over native species habitats.

  • Invasive SpeciesMany invasive species have been introduced intentionally.

  • Invasive SpeciesPrevention is the best way to reduce threats from invasive species, because once they arrive it is almost impossible to slow their spread.

  • PopulationHuman populations put pressure on speciesDirect use, habitat conversion, pollutionLarge numbers of humans use resources wild species needEven if each person uses small amounts of resourcesA small group of people can overuse resourcesPeople with highly consumptive resources have a disproportionate effect on the environmentDifferent levels of consumption and numbers of people drive tensions between countries

  • Figure 55.0 Deforestation of tropical forests

  • P. PollutionDamage to habitat by pollutionThree types of pollution: AirWaterLand

  • O. OverexploitationSome 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.

  • OverexploitationRhinoceros are often killed for their horns and sold illegally on the black market for decorative and medicinal purposes.

  • Overexploitation Case Study: Rising Demand for Bushmeat in AfricaBushmeat hunting has caused the local extinction of many animals in West Africa.

    Can spread disease such as HIV/AIDS and ebola virus.

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