Joshua Tree National Park is immense, nearly 800,000 acres, and infinitely variable. It can seem unwelcoming, even brutal during the heat of summer when, in fact, it is delicate and extremely fragile. This is a land shaped by strong winds, sudden torrents of rain, and climatic extremes. Rainfall is sparse and unpredictable. Streambeds are usually dry and waterholes are few. Viewed in summer, this land may appear defeated and dead, but within this parched environment are intricate living systems waiting for the opportune moment to reproduce. The individuals, both plant and animal, that inhabit the park are not individualists. They depend on their entire ecosystem for survival.
Two deserts, two large ecosystems primarily determined by elevation, come together in the park. Few areas more vividly illustrate the contrast between “high” and “low” desert. Below 3,000 feet (910 m), the Colorado Desert (part of the Sonoran Desert), occupying the eastern half of the park, is dominated by the abundant creosote bush. Adding interest to this arid land are small stands of spidery ocotillo and cholla cactus.The higher, slightly cooler, and wetter Mojave Desert is the special habitat of the undisciplined Joshua tree, extensive stands of which occur throughout the western half of the park. According to legend, Mormon pioneers considered the limbs of the Joshua trees to resemble the upstretched arms of Joshua leading them to the promised land. Others were not as visionary. Early explorer John Fremont described them as “…the most repulsive tree in the vegetable Kingdom.”