The California Fish and Game Commission voted unanimously on April 18 to “uplist” the Mojave desert tortoise from its previous status of “threatened” to an endangered species under the California Endangered Species Act during its meeting in San Jose.
According to executive summary with regard to the item on the meeting agenda, “Based upon a scientific review of its distribution and status, this petition requests that the Agassiz’s desert tortoise (Gopherus agassizii; Mojave desert tortoise or desert tortoise) be moved from listed as threatened to endangered by the California Fish and Game Commission. Despite federal and state protections, the desert tortoise is closer to extinction than it was in 1989 and 1990 when it was listed by the California Fish and Game Commission and U.S. Fish and Wildlife Service, respectively. A change in listing from Threatened to Endangered will reflect the current dire situation facing California’s state reptile and is necessary to generate substantially increased attention and efforts to reverse the very real likelihood that desert tortoise will become extinct in California.”
According to the summary, “Thirty-years after its listing as threatened under provisions of the California Endangered Species Act and the Endangered Species Act, Agassiz’s desert tortoise is in worse condition with the species on a path to extinction due to an increase in the number and severity of threats. Similarly, while critical habitat was designated for this species in 1994 and several federal resource management plans have been adopted by the Bureau of Land Management and designed to improve habitat conditions, the sobering reality is that conditions on the ground have worsened for Agassiz’s desert tortoise habitat over the long term, especially in California. More development and increased human uses have occurred in the California desert since listing, resulting in substantial loss of individuals, reduced recruitment, and substantial loss/degradation of habitat. Further, these threats are amplified by the effects of climate change on tortoise habitat. As a result, tortoise populations throughout all recovery units in California continue to decline. Reversing the trend towards extinction and putting Agassiz’s desert tortoise on a path towards recovery is difficult because the tortoise is a long-lived reptile, requiring up to 20 years to reach sexual maturity, and has a low reproductive rate over a long period of reproductive potential. The combination of a late breeding age and a low reproductive rate makes accomplishing desert tortoise recovery very challenging. In addition, the continued, ongoing loss and degradation of the species’ last remaining occupied habitat from a variety of authorized and unauthorized land uses, in an area of increasing human population growth, renewable energy development and generation, motorized vehicle recreation, and other human impacts, only makes the conservation and recovery of the desert tortoise even more challenging.” The report states, “Threats to the species at the time of the 1990 federal listing as threatened have not abated. Instead, they are more widespread and intense. The relatively recent expansion of military testing and training installations (United States Army National Training Center, Fort Irwin; United States Navy, Marine Corps Air Ground Combat Center, Twentynine Palms); development of large-scale renewable energy projects throughout the range of Agassiz’s desert tortoise; and increased human population growth and activities in the California desert have resulted in concurrent tortoise mortality and habitat degradation/loss, both adjacent to human communities and at appreciable distances. Notably, tortoise populations located immediately adjacent to expanding human communities have disappeared. Tortoises and their habitats are impacted by a myriad of authorized and illegal human activities that degrade or eliminate suitable creosote bush scrub and other vegetation communities needed as habitat. In particular, off-highway vehicle use, especially widespread, unregulated use on lands that are supposed to be protected, destroys and fragments habitat, injures and kills tortoise, and crushes tortoise burrows and eggs. Human activities also subsidize predators whose increased numbers prey on tortoises and facilitate invasion of non-native species of plants that degrade habitat quality and displace native forbs and grasses needed for adequate nutrition and reproduction/recruitment. Invasive, non-native plants also increase flammable fuel load to the point where wildfire, when it occurs, results in catastrophic megafires that kill tortoises outright. Recovery from fire in Mojave and Colorado desert vegetation communities is extremely slow because these communities are not adapted to wildfire and non-native plants outcompete native species during the post-fire period.”
The tortoises population has declined most markedly in the western Mojave Desert, where a survey found a 54 percent reduction in the number of animals between 2001 and 2020, representing the loss of 112,000 adult animals, according to California Fish and Game Commission staff. Simultaneously, the eastern Mojave Desert region saw a 10 percent tortoise population reduction, equal to 5,000 tortoises. The Colorado Desert saw a decrease of 17 percent, or roughly 13,000 tortoises.
Ravens, which prey upon juvenile tortoises represent a major threat to the species. The population of ravens has dramatically increased in the
Mojave desert tortoise’s range over the past 50 years.
In a joint letter to the Fish and Game Commission. dated March 29 from Jeff Aardahl of Defenders of Wildlife, Ed LaRue of the Desert Tortoise Council and Ron Berger of the Desert Tortoise Preserve Committee, the trio stated that “the Mojave Desert Tortoise is in serious danger of becoming extinct in California due to one or more causes including present or threatened degradation and loss of habitat, predation, and other natural occurrences and human-related activities. Listing the desert tortoise as endangered will likely increase allocation of funds for actions that are proven to be effective in conserving the species and its habitat. Listing the species as endangered may also provide a regulatory environment where greater scrutiny of the adverse impacts of proposed land uses will occur and impact avoidance and mitigation requirements will be more effective and enforced.”