Defenders was influential in having the Mojave population of the desert tortoises listed as a threatened species under the Endangered Species Act  in 1989 and 1990, and in having its Critical Habitat designated in 1994.
Over the past several decades, Defenders has been and continues to be an outspoken advocate for conservation of desert tortoises – both their habitats  and existing populations. Defenders staff have challenged many federal, state and local government agency programs and permits allowing for excessive human activities and developments in desert tortoise habitats, and rallied our supporters to do the same. These challenges have addressed excessive and improper livestock grazing, off-road vehicle use, military base expansion and renewable energy generation and electrical transmission projects.
Defenders has two full-time staff biologists dedicated to conservation of the natural biological communities in the Mojave Desert region, including remaining populations of the threatened desert tortoise and its habitat. Our most challenging work now involves large-scale solar energy projects planned in remote desert  landscapes that support significant numbers of desert tortoises. We spend considerable time trying to convince solar energy companies to locate their projects to degraded lands with little or no long-term conservation value for desert tortoises. We also work closely with federal and state agencies to develop policy decisions on solar energy projects that will protect important desert tortoise populations and their habitats. As a last resort, Defenders legally challenges agency decisions approving large-scale renewable energy projects that threaten desert tortoises, their habitat and their future recovery.
In California , Defenders actively supports the U.S. Fish and Wildlife Service in developing a desert tortoise recovery action plan for habitat located in California. As a member of the recovery plan implementation team, Defenders staff has an opportunity to recommend implementing professional, science-based recovery actions to address the most serious threats facing the species and its remaining habitat.