Can the U.S. Endangered Species Act protect biodiversity from climate change effects? Post-Weyerhaeuser unoccupied critical habitat designations

Unoccupied critical habitat designation is often highlighted as a beneficial U.S. Endangered Species Act provision for conserving biodiversity in the face of climate change. However, the effectiveness of this legal mechanism may be at risk due to the U.S. Supreme Court’s 2018 ruling in Weyerhaeuser Co. v. the U.S. Fish and Wildlife Service (FWS) and resulting shifts in federal rules regulating unoccupied critical habitat designations. This project examines how the FWS navigated the first Trump administration’s regulatory changes following Weyerhaeuser in proposed rules for three South Florida reptile taxa threatened by climate change effects. The FWS proposed designating unoccupied critical habitat for the Florida Keys mole skink ( Eumeces egregius egregius ) and the rim rock crowned snake ( Tantilla oolitica ). However, they determined that unoccupied critical habitat was not essential for the conservation of the Key ring-necked snake ( Diadophis punctatus acricus ) despite its entire occupied habitat being vulnerable to sea level rise. The FWS contended that these proposed critical habitat designations would have been the same whether finalised under the Trump administration’s post-Weyerhaeuser regulations or prior regulations. Textual evidence demonstrates that the FWS likely drew on the Trump administration’s more stringent language and criteria for proposing unoccupied critical habitat units even when finalising analyses under less stringent regulations. Along with drawing broader lessons about how conservation law might adapt to the climate crisis, the study cautiously advocates for designating unoccupied critical habitat for the Key ring-necked snake for future assisted migrations provided the potential risk of hybridisation is considered.