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
Lop Desert Lop Desert The Lop Desert, or the Lop Depression, is a desert extending from Korla eastwards along the foot of the Kuruk-tagh (meaning Dry Mountain) to the formerly terminal Tarim Basin in the Xinjiang Uyghur Autonomous Region of China. It is an almost perfectly flat expanse with no topographic relief. Lake Bosten in the northwest lies at an altitude of , while the Lop Nur in the southeast is only 250 m lower. The Lop Desert is on the whole flat, but with three slightly more depressed areas which might form lakes if filled with water - the Lop Nor