Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

View Data for At-Risk Plant Species View Data for At-Risk Animal Species

What is This Indicator and Why Is It Important? This indicator reports on the relative risk of extinction of native plant and animal species. The degree of risk for any particular plant or animal species varies considerably, from those species at little or no risk, to those that are in imminent danger of extinction. The data cover many of the best-known groups of native plants and animals, totaling about 22,000 native species.

Each species is ranked on such factors as the number and condition of individuals and populations, population trends, the area occupied by the species, and known threats. For example, “critically imperiled” species often are found in five or fewer places, may have experienced very steep declines, or show other evidence of very high risk. “Imperiled” species often are found in 20 or fewer places, may have experienced steep declines, or display other risk factors. “Vulnerable” species often are found in fewer than 80 places, may have recently experienced widespread decline, or show other signs of moderate risk. The remaining plant and animal species are regarded as “secure” or “apparently secure.” In all cases, a wide variety of factors contribute to overall ratings.

Increased risk levels for a particular species may be due to historical or recent population declines, or they may reflect natural rarity; biologists often consider very rare species to be at risk even in the absence of recent declines or current threats.

Species are valued for a variety of reasons: they provide products, including food, fiber, and genetic materials; they serve as key elements of ecosystems, which provide valuable goods and services; and many people value them for their intrinsic worth or beauty.

What Do The Data Show? About 19% of native animal species and 15% of native plants species in the U.S. are ranked as “imperiled” or “critically imperiled,” and another 1% of plants and 3.5% of animals may already be extinct—that is, they have not been located despite intensive searches. When “vulnerable” species are counted, about one-third of plant and animal species are considered to be “at risk.”

Hawaii has a much higher percentage of at-risk plants and animals than any other region, followed by the Pacific Coast. In contrast, the Midwest and Northeast/Mid-Atlantic have the lowest percentages.