Climate Attribution Science and The Endangered Species Act

By Jessica Wentz

Climate change poses an enormous risk to plant and animal species across the planet. Mean global temperatures have already increased by approximately 1ºC, causing environmental changes that affect species abundance, distribution, behavior, physiology, genetics, and survival prospects. These changes, combined with other human stressors, have already resulted in the extinction of some species and imperiled many others. Some scientists describe this as the “Holocene” or “Anthropocene” mass extinction event. The fate of many vulnerable species will depend on emissions trajectories and mitigation efforts. But there is also a compelling need for adaptive species management in the context of a changing climate.

In the U.S., the Endangered Species Act (ESA) is the primary legal vehicle for the protection and management of species at risk of extinction. The statute and accompanying regulations outline a science-based framework for identifying endangered and threatened species, establishing critical habitat boundaries, and mitigating the harmful impacts of public and private-sector activities on listed species. Although climate change is not explicitly mentioned in the statute, there is no question that agencies must consider climate-related threats when implementing the ESA.

This article examines how climate science, particularly climate change detection and attribution research, can be used to improve ESA listing and management decisions. The article begins by focusing on how attribution research – which links existing, observed impacts to climate change – has been used in the courtroom to compel or defend consideration of climate change impacts in agency rulemaking and planning under the ESA. One key finding is that attribution research can help to persuade courts of the credibility of future predictions of climate change, which are particularly relevant when assessing long-term threats to species. Attribution science also supports proactive measures undertaken to protect species against climate-related threats, such as the designation of critical habitat in areas that are presently unoccupied by the species but nonetheless valuable as future refugia or habitat corridors. Agencies cannot ignore attribution research on the basis of uncertainty or imprecision where the data suggests that there is a probable threat to a species. 

The article concludes with recommendations and best practices pertaining to the use of climate attribution data in ESA management and litigation. It outlines areas where additional guidance may help agencies improve and standardize their approach to climate impact analysis, as well as regulatory amendments that could improve the consideration of climate science in ESA decision-making and enable agencies to make better management decisions in light of their scientific analysis.