The environmental group Center for Biological Diversity said it has filed a laswuit to block the implementation of Los Angeles County’s Antelope Valley Area Plan, approved by the Board of Supervisors June 16.

The equivalent of the “One Valley One Vision” plan for the Santa Clarita Valley, the Antelope Valley Area Plan covers 1,800 square miles of mostly rural areas of northern Los Angeles County – such as Gorman, Acton, Green Valley and the Lake Communities.

Included within the planning area boundary is property in the northwest corner of the county where the Tejon Ranch Co. plans to develop an eventual 20,000-home community called Centennial along the L.A.-Kern county line.

The area features an incredible variety of landscapes, including rugged mountains, deserts, forests, native grasslands, oak savannahs, playa lakes, stunning wildflower fields, scenic vistas and dark night skies. It is also home to a great diversity of wildlife and plants, including the California condor, desert tortoise, pronghorn, arroyo toad, least Bell’s vireo, Santa Ana sucker, unarmored threespine stickleback, Nevin’s barberry, Bakersfield cactus and thread-leaved brodiaea,” the environmental group said in a statement.

A press release from the Center for Biological Diversity follows:

The unincorporated parts of the Antelope Valley are mostly rural, agricultural or open-space lands. In June, however, the county adopted a new plan designed to facilitate large-scale future development. The Antelope Valley Area Plan would facilitate the creation of entirely new towns, including Tejon Ranch Co.’s Centennial project, which would add around 20,000 new houses to the northwestern part of the valley — development that is unsustainable in this arid but ecologically rich region.

The plan originally called for the expansion of the county’s system of Significant Ecological Areas — designated to protect unique and irreplaceable wildlife and plant communities — to help reduce the environmental harm from the new development the plan would promote. But the county board of supervisors scaled back the protection of “significant ecological areas” and made other changes to the plan that will make the plan’s environmental consequences even worse.

“The Antelope Valley Area Plan the board foisted on the public is not the same plan we reviewed and commented on in 2014,” said Ileene Anderson, a senior scientist with the Center. “As damaging and growth-oriented as the plan originally was, the approved plan is far worse.”

The Center’s lawsuit contends that the county violated the California Environmental Quality Act when it approved the new Antelope Valley Area Plan.