The United States Fish and Wildlife Service determined on October 5, 2015 that the Sonoran Desert Tortoise, found primarily in Arizona, does not qualify as either an endangered or threatened species under the Endangered Species Act. The decision was the culmination of a 12-month review finding that there were between 470,000 and 970,000 adult desert tortoises occupying a range of roughly 38,000 square miles of potential habitat. The review also found that voluntary collaborations between state and federal agencies, landowners and developers ensured the continued protection of the species. The decision has been lauded by developers, but environmental groups have criticized the decision and pledged to “look closely” at its reasoning.
Background
The Sonoran Desert Tortoise (Gopherus morafkai) occupies portions of western, northwestern and southern Arizona, and the northern two-thirds of the Mexican State of Sonora. The species lives primarily in rocky, steep slopes in various desert scrub habitats. The Sonoran Desert Tortoise has been recognized as a species distinct from the Mojave Desert Tortoise (Gopherus agassizii) only since 2012. Prior to that time, the Sonoran Desert Tortoise was recognized informally as the “Sonoran population” of the Mojave Desert Tortoise, which was generally referred to as the “desert tortoise.” The Mojave Desert Tortoise has been listed as a threatened species under the ESA since April 1990.
On October 15, 2008, WildEarth Guardians and Western Watersheds Project filed a petition requesting that the Sonoran population of the desert tortoise be listed as a distinct population segment (DPS) that was threatened or endangered. The FWS found in August 2009 that the petition presented “substantial scientific information indicating that listing the Sonoran DPS of the desert tortoise may be warranted,” and in December 2010, the FWS determined that while the Sonoran DPS warranted listing, it was precluded by other “higher priority actions.” The Sonoran DPS was accordingly added to the list of candidate species for future consideration.
Candidate status for the Sonoran DPS was reaffirmed in both 2011 and in 2012, after the Sonoran Desert Tortoise was recognized as its own species. In 2011, the FWS agreed to make a final determination on whether the species qualified as threatened or endangered by the end of September 2015.
Decision
The FWS decision found that “robust scientific analysis” illustrated that the Sonoran Desert Tortoise population is adequately protected from both natural and anthropogenic stressors. The decision analyzed six primary risk factors: (1) altered plant communities; (2) altered fire regimes; (3) habitat conversion of native vegetation to designed landscapes; (4) habitat fragmentation; (5) human-tortoise interactions; and (6) climate change and drought. The decision found that while some or several of these factors could have effects on individual tortoises, “most have not been shown or are not expected to have population-level effects on the species.” While the decision recognized that the life history and longevity of the species rendered it impossible to reasonably predict population-level effects in the future, it also emphasized that Sonoran Desert Tortoise populations are not known to be in decline anywhere in the state due to individual or cumulative impacts.
The decision specifically focused on the fact that the majority of the Sonoran Desert Tortoise’s potential habitat in Arizona was not likely to be developed. Specifically, the decision noted that an estimated 73% of potential tortoise habitat was not compatible with widespread development because it included military lands, state and municipal parks and areas owned by the Bureau of Land Management, Bureau of Reclamation, National Park Service, U.S. Forest Service and FWS. Only 5% of Arizona’s 1,279 square miles designated as urban is considered potential tortoise habitat.
Additionally, the decision noted the effect of various conservation measures and land management practices that were implemented after the Sonoran Desert Tortoise was listed as a candidate species. Most notably, a candidate conservation agreement was executed in March 2015 between the Bureau of Land Management, U.S. Department of Defense, National Park Service, FWS, Bureau of Reclamation, Customs and Border Protection, Forest Service, Natural Resources Conservation Service, Arizona Game and Fish Department and Arizona Department of Transportation. Participants to the agreement voluntarily committed to implement specific actions designed to remove or reduce stressors to the Sonoran Desert Tortoise. Parties to the agreement identified existing tortoise conservation measures and management actions needed, including, but not limited to, reducing the spread of nonnative grasses, reducing or mitigating dispersal barriers, reducing the risk and impact of desert wildfires, reducing the impact of off-highway vehicles, monitoring population and reducing illegal collection of tortoises. The agreement applies to approximately 13,000 square miles of Sonoran Desert Tortoise habitat in Arizona, which represents 55% of the species’ predicted potential habitat in Arizona and 34% of its predicted potential habitat rangewide.
Implications
There was substantial concern that given the Sonoran Desert Tortoise’s significant habitat range in Arizona, listing it under the ESA could significantly hamper solar power development in the state. Residential and commercial developers expressed a similar concern, as both activities require substantial altering and grading of desert habitat. The decision by the FWS eliminates those concerns—at least for the foreseeable future. While environmental groups have criticized the decision as “not warranted,” claiming that it ignores looming threats to the species from climate change and drought, no groups have yet overtly threatened to sue the FWS for its decision. Such a lawsuit, however, remains a possibility.
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