Drake said it will take at least another year to know how best to restore the habitat and deal with the increasing problem of non-native cheat grass, red brome and Sahara mustard. The weeds serve as flash fuels for wildfires. Scientists’ attempts to reseed charred areas with native plants that tortoises eat have not been successful so far, said Lori Rose, a biologist for Washington County, Utah. Rose said the expensive technique leaves about 140 to 200 seeds per square meter, compared to 6,000 seeds under normal conditions. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! LAS VEGAS – Wildfires fueled by invasive weeds in the Mojave Desert are threatening federally protected desert tortoises, scientists say. Biologists, who gathered Friday for a meeting of the Desert Tortoise Council, said the fires in 2005 burned more than 1 million acres of desert tortoise habitat in the Mojave Desert region that spans southern parts of Nevada, Utah, California and northern Arizona. Among the burned acreage was 32,000 acres of designated critical habitat for the desert tortoise in southern Nevada, according to Kristina Drake of the U.S. Geological Survey in Henderson, Nev. Biologists estimate a 40 percent to 50 percent mortality rate for desert tortoises in burned areas of southern Utah.