• 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.
  • 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.
  • Some species have characteristics that make them vulnerable to ecological and biological extinction.
  • Percentage of various species types threatened with premature extinction from humanvan activities.


  • Conservation biologists summarize the most important causes of premature extinction as “HIPPO”:
  • Habitat destruction, degradation, and fragmentation
  • Invasive species
  • Population growth
  • Pollution
  • Overharvest
  • Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest.
  • Case Study:
    A Disturbing Message from the Birds
  • Human activities are causing serious declines in the populations of many bird species.


  • Many 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.
  • Many invasive species have been introduced intentionally.
  • Many invasive species have been introduced unintentionally.


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


  • 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.
  • 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.
  • The U.S. Endangered Species Act
  • Biodiversity hotspots in relation to the largest concentrations of rare and potentially endangered species in the U.S.
  • Because of scarcity of inspectors, probably no more than 1/10th of the illegal wildlife trade in the U.S. is discovered.
  • The U.S. has set aside 544 federal refuges for wildlife, but many refuges are suffering from environmental degradation.


  • Involves troposphere
    • Substances involved: greenhouse gases that trap heat (CO2, CH4, N2O)
    • Problem:  burning of FF, deforestation increase trapping of heat and increase Earth’s temp.
    • Consequences: changes in climate, agric. productivity, H2O supplies, and sea level
    • Responses: decrease fossil fuel use and deforestation; prepare for climate change
    • Ozone Depletion
      • Involves stratosphere
      • Substances involved: O3, O2, CFC’s
      • Problem: human activities and CFC’s destroy ozone allowing more UV radiation to reach Earth
      • Consequences:  increase skin cancer, cataracts, damage to crops/phytoplankon
      • Responses: Eliminate/substitute for CFC’s and ODC’s
author avatar
William Anderson (Schoolworkhelper Editorial Team)
William completed his Bachelor of Science and Master of Arts in 2013. He current serves as a lecturer, tutor and freelance writer. In his spare time, he enjoys reading, walking his dog and parasailing. Article last reviewed: 2022 | St. Rosemary Institution © 2010-2024 | Creative Commons 4.0

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