Desert bighorn sheep establish two desert areas in southwestern Arizona to help preserve the desert bighorn sheep: Cabeza Prieta National Wildlife Refuge and the Kofa National Wildlife Refuge. In 1941, the San Andres National Wildlife Refuge in New Mexico was added. Desert bighorn sheep populations have trended upward since the 1960s when their population was estimated at 6,700-8,100. The upward trend was caused by conservation measures, including habitat preservation. In 1980, desert bighorn sheep populations were estimated at 8,415-9,040. A state-by-state survey was conducted a few years later and estimated the overall US desert bighorn sheep population at 15,980. The 1993 estimate of
Solar power plants in the Mojave Desert photovoltaic power station approximately six miles north of Desert Center, California, in the Mojave Desert. It uses approximately 8.8 million cadmium telluride modules made by the US thin-film manufacturer First Solar. As of Fall 2015, the Solar Farm has the same 550 MW installed capacity as the Topaz Solar Farm in the Carrizo Plain region of Central California, making both of them tied for the second largest completed solar plants by installed capacity. Nevada Solar One has a 64-MW generating capacity and is located in Boulder City, Nevada. It was built by the U.S. Department of Energy, National Renewable Energy