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1) The Extinction Crisis:

The human species, one of millions of life forms on this planet, is threatening the very existence of many other species. Biological diversity, or biodiversity, is the variety of life forms that interact tosupport and sustain the balance of nature.

2) Why it Matters:

Should it matter to humans that other life forms are disappearing? Many people think so. Human populations depend on plants and animals for much of their food, medicines, clothing, and shelter.

3) Threatened and Endangered Species:

Under the Endangered Species Act in the United States, a species or subspecies is regarded as "endangered" when it is in danger of extinction throughout all or a significant part of its normal range.

4) The Causes: Habitat Loss:

The most common cause of endangerment is habitat loss. Plants and animals need space to live and energy provided by food, just as humans do. As human population and consumption increase, wildlife habitat is converted to houses and highways. Forests are cut down for building materials, fuel, and paper.

5) The Causes: Overexploitation:

Humans also deplete wildlife populations by capturing or killing individuals for their own use. Animals are killed for food, fur, feathers, oil, medicines, crafts, and a host of other uses. They are also shot to stop them from killing livestock, or simply for sport.

6) The Causes - Introduced Species:

Humans often move species around, introducing species that are not native to an ecosystem and disrupting the delicate balance that evolved among species in that ecosystem. Species can be moved both accidentally and intentionally. The introduced species may compete with native species for food or nest sites, or they may prey on native species.

7) The Causes - Polution:

One of the ways habitat is degraded is by pollution. Creatures that depend on either freshwater or saltwater for all or part of their life cycles, like fish, frogs, marine mammals, and many invertebrates, are especially vulnerable to pollution.

8) The Causes - Other Factors:

We know less about other factors that probably contribute to the decline of biological diversity. We know little about how changes in our atmosphere, such as global warming or ozone depletion, is affecting other life forms.

9) Conservation Biology:

The new discipline of conservation biology has developed to respond to the increased threats to biological diversity. Its main goals are to determine human impacts on other species and to develop practical solutions to reduce the extinction rate.

10) Conservation Actions:

There are many ways conservation biologists are addressing the extinction crisis. These include 1) Establishing protected areas where wildlife habitat is preserved or restored 2) Developing new ways to farm, log, and graze livestock, that preserve habitat values; and many more...

11) Questions for Thought:

Society does not have the resources to save every species from human-caused extinction. How should we decide where to put our energy and resources in conserving species? Should we concentrate on the species people like best, the "charismatic megafauna?" What other criteria might we use?