That’s because those animals found in California, Nevada and Utah that have been designated as a separate species – called Agassiz’s desert tortoise (Gopherus agassizii) after a 19th century biologist – now occupy a much smaller range.
The Agassiz’s desert tortoise’s Mojave Desert home, north and west of the Colorado River, constitutes only 30% percent of the desert tortoise’s previous habitat. The remainder of that range is now home to a new species christened Morafka’s desert tortoise – as a tribute to a California biologist named David J. Morafka – that roams the Sonoran Desert south and east of the Colorado River from Arizona through Mexico.
“This reduction has important implications for the conservation and protection of Gopherus agassizii, which may deserve a higher level of protection,” wrote the biologists who authored the paper, published in the journal ZooKeys. “Whereas species with broad distributions may survive population declines, those that have small distributions are far more likely to become extinct.”
“Given drastic population declines of G. agassizii during the past few decades, it might be endangered,” they added.
The United States Fish and Wildlife Service already manages the Mojave and Sonoran populations separately and a spokeswoman said the new species designations will not change the way the agency analyzes the impact of solar power plants on the Agassiz’s desert tortoise.
“We independently evaluated the Mojave population of desert tortoise and there is no evidence to suggest the species is expected to go extinct, which is the threshold for uplisting to endangered status,” Jeannie Stafford, a public affairs officer in the agency’s Nevada office, said in an email. “We do not anticipate any changes in the way development projects will be evaluated for the Agassiz’s desert tortoise in the future.”
But some environmental groups most likely will press for closer scrutiny of the dozen big solar farms planned for the Mojave.
“We’re seeing some very large solar projects on public lands that are having a very big impact on tortoise populations,” says Lisa Belenky, an attorney with the Center for Biological Diversity, which litigates aggressively on behalf of wildlife and which has been involved in the licensing of solar power plants in California. “The threats have been increasing and the populations decreasing, and based on those factors alone, we have already been considering whether there needs to be an uplifting to endangered species status for the desert tortoise.”
“The new desert tortoise species certainly helps frame those issues even more clearly,” she adds.
Kristin Berry is one of the paper’s authors and a biologist with the U.S. Geological Survey in Southern California who is a leading authority on the desert tortoise. She says the identification of Agassiz’s desert tortoise as a separate species should spur efforts to protect its habitat.
“In terms of conservation biology, when a species’ range is reduced by 70% one looks at what to do so habitat is adequately protected,” says Berry. “It’s a very important issue.”
Morafka’s desert tortoise, meanwhile, currently is not listed as a protected species. The government put the critter on an endangered species candidates list after it determined protection was warranted but precluded by a lack of resources and other animals facing even greater threats.
However, a legal settlement that environmental group WildEarth Guardians struck with the Fish and Wildlife Service in May requires the agency to move the tortoise off the candidates list by 2015.