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.
- 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.
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
- 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.
INVASIVE 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.
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.
- 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.
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.
- 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.
- 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.
GLOBAL WARMING
- 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
