desert

Desert is a landscape characterized by extremely low precipitation and sparse vegetation. Most definitions use an average annual precipitation of less than 250 millimeters (about 10 inches); some areas receive less than 100 millimeters and are termed hyperarid. Deserts occur on every continent and cover about one third of Earth's land surface. They vary in temperature, from hot deserts with scorching days to cold deserts with frigid winters.

Desert climates are shaped by atmospheric circulation, topography, and proximity to oceans. Subtropical high-pressure belts, rain shadows behind mountains, and interior continental locations limit moisture. Daily temperature ranges can be extreme, and rainfall, when it occurs, is often infrequent and may take the form of short thunderstorms or rare showers. Landscape features include sand dunes, rocky plateaus, gravel flats, and salt flats; water bodies are rare and often ephemeral.

Plants and animals have evolved adaptations to conserve water. Plants such as succulents store water, develop extensive root systems, or shed leaves to reduce transpiration. In many deserts, photosynthesis is specialized (CAM or C4). Animals are often nocturnal or burrow to avoid heat; many obtain moisture from food or metabolic processes and are efficient in water use.

Humans have inhabited deserts for thousands of years, relying on nomadic herding, oasis agriculture, and mining. Desertification, land degradation from overuse, drought, or climate change, threatens ecosystems and livelihoods. Deserts today host research, tourism, and renewable energy projects, including solar farms in suitable regions.

Prominent deserts include the Sahara, Arabian, Gobi, Kalahari, Mojave, and Atacama, among others, each with unique histories and ecosystems.