On either side of the southwest entrance to the Natural History Museum are desert vegetation representing the three types of deserts found in California. Deserts are places of high temperatures and low and erratic rainfall. Only specialized plants live there and there are 85 endemic (found nowhere else) species.
Sagebrush dominates the Great Basin High Desert of eastern California and northern Nevada. Its small, gray-green leaves are waxy to conserve moisture and reflect heat. The intense smell and taste of sage are ways to discourage grazers such as deer, pronghorns and wild horses from eating the plants to extinction. Deep roots allow them to obtain water better than most other competing plants in a dry land. Thermal springs occasionally provide local oases for larger plants in an otherwise dry environment. The elevation averages 4000 feet and above.
The Mojave Desert in southeastern California is a warm dry desert which ranges from below sea level to 4500 feet. It receives only 4 to 15 inches of rain a year, mostly in winter. Joshua trees, prickly pear cactus and Mojave yucca have narrow leaves and deep taproots as well as a network of shallow roots to take full advantage of infrequent rains. There is a desert pupfish pond here. Pupfish are survivors of drying and shrinking ice age lakes. These 1 to 2 inch fish can survive the widest range of temperatures (32° to 90°) of any fish. They are in danger of extinction because of human water use patterns and shrinking habitat.
The Sonoran, or Colorado Desert of Sonora, Mexico and Arizona, gets even less rain—2 to 5 inches—and elevations from sea level to 2000 feet are found here. It has a wide variety of drought-tolerant plants with adaptations such as fleshy pads and stems to store water and leaves reduced to spines. These minimize water loss and keep them from being eaten by large herbivores. Mesquite leaves grow perpendicular to the sun's rays overhead. The Sonoran desert covers 120,000 square miles in the U.S. and Mexico. There are as many as 3500 native species of plants, 130 mammal species, 500 bird species, 20 amphibians, 100 reptiles and 30 native freshwater fish.