LOS ANGELES: On a strip of California’s Mojave Desert, two dozen rare tortoises could stand in the way of a sprawling solar-energy complex in a case that highlights mounting tensions between wilderness conservation and the nation’s quest for cleaner power.

Oakland, Calif.-based BrightSource Energy has been pushing for more than two years for permission to erect 400,000 mirrors on the site to gather the sun’s energy. It could become the first project of its kind on US Bureau of Land Management property, leaving a footprint for others to follow on vast stretches of public land across the West. The construction would come with a cost: Government scientists have concluded that more than 6 square miles of habitat for the federally threatened desert tortoise would be permanently lost.

The Sierra Club and other environmentalists want the complex relocated to preserve what they call a near-pristine home for rare plants and wildlife, including the protected tortoise, the Western burrowing owl and bighorn sheep. “It’s actually a good project. It’s just located in the wrong place,” said Ileene Anderson of the Center for Biological Diversity, a Tucson, Arizona-based environmental group.

The dispute is likely to echo for years as more companies seek to develop solar, wind and geothermal plants on land treasured by environmentalists who also support the growth of alternative energy. In an area of stark beauty, the question will be what is worth preserving and at what cost as California pushes to generate one-third of its electricity from renewable sources by 2020.

The Bureau of Land Management has received more than 150 applications for large-scale solar projects on 1.8 million acres of federal land in California, Nevada, Arizona, New Mexico, Colorado and Utah. In California alone, such projects could claim an area the size of Rhode Island, transforming the state into the world’s largest solar farm.

BrightSource Energy wants permission to construct three solar power plants on the site that together would generate enough power each year for 142,000 homes, potentially generating billions of dollars of revenue over time. The sun’s power is used to heat water and make steam, which in turn drives turbines to create electricity. Built in phases, the project would include seven, 459-foot metal towers, a natural gas pipeline, water tanks, steam turbine generators, boilers and buildings for administration and maintenance. Each plant would be surrounded by 8-foot high steel fencing.

The site has virtually unbroken sunshine most of the year, and is near transmission lines that can carry the power to consumers.

Federal and state biologists reviewing the plan proposed that the company catch and move the tortoises and preserve them elsewhere on 12,000 acres, a proposal that could cost BrightSource an estimated $25 million.