9.9 Endangered Species

Extinction is the permanent loss of a species. It happens naturally, but human activity has made the current extinction rate far higher than the normal background rate. The main human causes are habitat loss, invasive species, pollution, climate change and overexploitation (topic 9.10).

Some species are much more vulnerable than others. Traits that raise extinction risk include:

• Specialist needs: a narrow diet or habitat, like a giant panda's dependence on bamboo (topic 3.1).
• K-selected traits: slow reproduction, few offspring and late maturity, so populations recover slowly after losses, like elephants, whales and condors (topic 3.2).
• Small population size or low genetic diversity, which leaves little room for losses and less ability to adapt.
• Small or isolated range, such as species found on only one island.
• Large body size and high place on the food chain, which mean large territory needs and small populations.
• Being hunted, fished or traded for valuable parts, such as rhino horn or elephant ivory.

The US Endangered Species Act (ESA), passed in 1973, lists species as endangered (in danger of extinction across all or much of their range) or threatened (likely to become endangered soon). It makes it illegal to kill, harm or harass listed species, requires federal agencies to make sure their actions don't jeopardize them, allows critical habitat to be designated, and calls for recovery plans. Success stories include the bald eagle, removed from the list in 2007, and the American alligator, removed in 1987.

CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora), signed in 1973, is an international treaty that controls trade in wild animals and plants and their parts. Species threatened with extinction are listed in its Appendix I, where commercial trade is banned; others are listed where trade is allowed only with permits. CITES fights poaching driven by international markets, such as the trade in ivory and rhino horn.

• Protecting and restoring habitat, which addresses the leading cause of endangerment.
• Captive breeding and reintroduction: the California condor fell to just 27 birds in 1987, when all were captured for breeding; releases have since rebuilt a wild population of several hundred.
• Reintroducing species to former ranges, like gray wolves returned to Yellowstone in 1995.
• Anti-poaching patrols, fishing and hunting limits, and reducing demand for wildlife products.
• Seed banks and gene banks that preserve genetic diversity.