Deserts: The World's Dry Places

A desert is any area that receives very little rainfall — fewer than 25 centimetres of rain per year. Deserts cover about one third of the Earth's land surface, making them the most common type of landscape. The word 'desert' comes from a word meaning 'abandoned' or 'empty', because so few plants and people can survive in such dry places.

Many people imagine every desert as endless golden sand, but this is a common mistake. In fact, only about a fifth of the world's deserts are sandy. Most are covered in bare rock, gravel, or pebbles, and some, like the cold deserts, are covered in ice. What truly makes a place a desert is the lack of rain, not the sand.

Hot deserts can be scorching during the day but bitterly cold at night. Because there are few clouds or plants to hold the warmth, the heat escapes quickly once the Sun sets, and temperatures can fall close to freezing. Sand dunes in hot deserts are shaped by wind blowing sand into huge, rippling hills that slowly move across the land over the years.

Animals have all sorts of clever ways to cope with the heat and lack of water. The fennec fox has enormous ears that let heat escape from its body, keeping it cool. Many small creatures, such as lizards and rodents, are nocturnal, which means they rest in burrows during the burning day and come out to hunt in the cool of the night.

Plants that live in deserts have clever tricks too. Cacti store water inside their thick stems and have spines instead of leaves to reduce water loss. After rare rains, some desert plants spring to life, flower quickly, and set seed before the ground dries out again. For a few days, a dry desert can suddenly burst into a carpet of colourful flowers.