Are we recovering? An evaluation of recovery criteria under the U.S. Endangered Species Act

In 1988, the Endangered Species Act was amended to require that recovery plans include objective criteria for delisting. In this paper, we characterized (1) temporal trends in the use of recovery criteria; (2) patterns of use for different categories of recovery criteria; (3) variability in the use of criteria by taxa and plan type; and (4) the relationship between categories of recovery criteria (population size, population trends, habitat fragmentation, demography, and legal/policy/other) and population status (i.e., declining, stable, improving). Of the 181 species (in 135 recovery plans) analyzed, 91% include at least one criterion, and 81% include at least one quantitative criterion. The total number of recovery criteria specified in plans increased significantly for species with plans approved after 1990. However, the number of recovery criteria characterized as having an unclear relationship to biological information also increased significantly for plans approved after 1990. Population size was the most quantitative and frequently used criterion, and there was a significant increase in the number of "population size" and "population trend" criteria with quantitative metrics after 1990. Species characterized as improving were more likely to include a very clear relationship to biological information. More recovery criteria are being developed for species in recent plans, and there is some evidence that species with improving status have a larger number of recovery criteria.