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.
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.