Dear EarthTalk: How are the world's reptile species faring in terms of population numbers and endangered status? What's being done, if anything, to help them? -- Vicky Desmond, Troy, N.Y.

The world's reptiles -- turtles, snakes, lizards, alligators and crocodiles -- are indeed in trouble. The International Union for Conservation of Nature, which publishes an annual global roster of threatened and endangered species called the Red List, considers some 664 species of reptiles -- representing more than 20 percent of known reptile species worldwide -- as endangered or facing extinction. Meanwhile, the U.S. Fish & Wildlife Service considers about 10 percent of American reptiles threatened or endangered.

Why care? The nonprofit Center for Biological Diversity (CBD) considers reptiles "amazing creatures" with clever adaptations that have helped them survive for millions of years. CBD also points out that reptiles are valuable indicators of wider ecological health.

"Because many reptile species are long-lived and relatively slow-moving, they suffer from disturbances like habitat loss or pollution for extended periods," the group reported, adding that a diverse community of reptiles living in a given area is evidence of a healthy ecosystem that can support the plant and animal life they and other species need for food and cover.

So what's causing the reptiles' decline?

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"While habitat loss is the most obvious cause of endangerment, declines are even occurring in pristine areas from threats such as disease, UV radiation and climate change," reported CBD. Overcollecting and unregulated hunting also are taking a toll on reptile populations.

In order to help stem the tide of reptile loss, CBD leverages the court system to pressure the federal government to protect at-risk species. For instance, back in 2004 the group worked with the Coalition for Sonoran Desert Protection in filing a petition to add the Tucson shovel-nosed snake, which dwells in the quickly disappearing wild desert around fast-growing cities like Tucson and Phoenix, to the federal list of endangered species.

Contacts: CBD, www.biologicaldiversity.org; Patuxent Wildlife Research Center, www.pwrc.usgs.gov.

EarthTalk is by Roddy Scheer and Doug Moss of E -- The Environmental Magazine (www.emagazine.com). Send questions to earthtalk@emagazine.com.