Species Endangerment Patterns In The United States

A supporting technical document for the 1993 Update of the 1989 RPA Assessment

Concern for increased rarity among the Nation's animals and plants has grown rapidly in the past decade. Although biodiversity is an attribute of ecological systems that cannot be simply quantified, there is little disagreement that diversity diminishes as species become extinct. Consequently, much of the interest in rare species stems from the assumption that those species are the most prone to extinction, and that by understanding the processes that have contributed to their rarity, further losses of diversity may be slowed or reduced. This report examines the likely future distributional patterns of threatened and endangered species.

Highlights include the following:

• Endangered biota are not homogeneously distributed across the United States.
• Threatened and endangered species show a strong nonrandom pattern in their occurrence, which can be used to identify distinct regions with high endangerment potential relative to other regions.
• Regions supporting many endangered species were located in the Southeastern and Southwestern United States.
• Candidate species for federal threatened or endangered status are also concentrated in the present regions of endangerment.
• Among other factors, droughtstress climates and land use intensification were associated with high species endangerment.

Flather, Curtis H; Joyce, Linda A.; Bloomgarden, Carol A. 1994. Species endangerment patterns in the United States. Gen. Tech. Rep. RM241. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 42 p.