A widespread gap in U.S. Endangered Species Act implementation: Risk of genetic erosion within populations

Despite its importance to fitness and population viability, genetic diversity is rarely incorporated into biodiversity assessments. The recent adoption of indicators of intraspecific genetic diversity by the Convention on Biological Diversity has highlighted the importance of evaluating genetic diversity in wild species. Genetic indicators are useful even in the absence of genetic data because they reflect two major drivers of genetic diversity: population size and the maintenance of populations across a species’ range. Here, we apply these indicators to 161 species assessed for classification under the U.S. Endangered Species Act (ESA), one of the strongest conservation laws in the world. We found that while most populations are being maintained across species’ ranges, many of those populations are likely at risk of genetic erosion, compromising their ability to maintain genetic diversity and evolutionary potential. Additionally, ESA classification status was not correlated with the genetic indicators, suggesting that genetic health is either not being incorporated into species assessments, or is not being given full consideration by decision-makers during determinations of classification status. Fortunately, we found that data were widely available to calculate the genetic indicators. We suggest that the genetic indicators are a useful tool for evaluating and communicating genetic health in ESA assessments in a transparent and standardized manner. Inclusion of genetic indicators could support more timely and better-targeted protection of at-risk species prior to irreversible losses of genetic diversity. This, in turn, would increase the success of recovery actions while reducing time to recovery and overall costs, better ensuring the ESA goal of safeguarding biodiversity.