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
Sahara Desert (ecoregion) east, and west by desert ecoregions with higher rainfall and more vegetation. The North Saharan steppe and woodlands ecoregion lies to the north and west, bordering the Mediterranean climate regions of Africa's Mediterranean and North Atlantic coasts. The North Saharan steppe and woodlands receives more regular winter rainfall than the Sahara Desert ecoregion. The South Saharan steppe and woodlands ecoregion lies to the south, between the Sahara Desert ecoregion and the Sahel grasslands. The South Saharan steppe and woodlands receives most of its annual rainfall during the summer. The Red Sea coastal desert lies in the coastal strip between the