Prickly Pear Cacti
The yellow bloom of a prickly pear cactus brightens this view of a California desert. Cacti are often thought of as a stereotypical desert plant, but they are rarely the dominant species in an area of desert.
Deserts may seem lifeless, but in fact many species have evolved special ways to survive in the harsh environments.
Far from being barren wastelands, deserts are biologically rich habitats with a vast array of animals and plants that have adapted to the harsh conditions there. Some deserts are among the planet's last remaining areas of total wilderness. Yet more than one billion people, one-sixth of the Earth's population, actually live in desert regions.
Deserts cover more than one-fifth of the Earth's land area, and they are found on every continent. A place that receives less than 10 inches (25 centimeters) of rain per year is considered a desert. Deserts are part of a wider class of regions called drylands. These areas exist under a “moisture deficit,” which means they can frequently lose more moisture through evaporation than they