WHAT IS A DESERT BIOME Most people think of deserts as hot and sandy but there are several different kinds of desert What makes a desert a desert is a lack of rain Most deserts get less than 10 inches 25 cm of rain a year whereas 80 inches 200 cm can fall in a rainforest every year Only one in ten of the world’s deserts has sand dunes Most like this one in northern Niger are rocky with occasional plants Different deserts Some deserts are large flat expanses of sand but others have rocks and mountains or hills of sand called dunes that can reach 1300 feet 400 m high Some deserts reach sizzling temperatures of 130 F 54 C or more while other deserts have chilly winters or are freezing cold all year like Antarctica Some deserts receive very light but regular rain showers others get all their annual rain in one heavy storm that lasts for just an hour Fact Focus Biome or Habitat Biomes are regions of the world such as deserts forests rivers oceans tundra and grassland that have similar climate plants and animals A habitat is the specific place in a biome where a plant or animal lives 4
Desert life Some deserts look empty and lifeless The lack of water and soil means that plants grow far apart to get a share of any water available But there is a rich variety of plant life ranging from saguaro cacti as tall as a four story house to plants that look like tiny stones see page 9 There are few trees to give shade so although there are some large animals such as camels most desert-dwelling animals are small Some such as desert tortoises have shells or tough scaly skin to protect them from the fierce temperatures Others such as ground squirrels make burrows under the ground to escape the daytime heat The Cape ground squirrel has a long very bushy tail that it uses like an umbrella to provide shade when it is feeding in the hot Kalahari Desert Amazing Adaptation Adaptations are special features or body parts that living things develop over time to help them survive in a biome Mammals such as camels that live in hot deserts have very furry backs to protect them from the burning sun 5
WHERE ARE DESERTS There are four different types of deserts subtropical coastal semi-arid and polar that cover about one fifth of Earth’s land surface Subtropical deserts Many of the world’s deserts including the Sahara Desert in Africa and the Sonoran Desert in North America are subtropical Very hot moist air rises above the equator condenses and falls as heavy tropical rains in rain forests The air is now very dry as it moves to the north and south of the equator creating deserts in subtropical areas Polar deserts Antarctica is the driest desert of all More than 98 percent of Antarctica is covered with ice and there is no rain only snow so there is almost no liquid water at all Amazing Adaptation The Couch’s spadefoot toad sheds layers of skin to create a watertight covering over its body This prevents water from escaping from the toad’s body helping it survive dry periods underground These toads can eat enough insects in one or two nights to survive for up to a year 6 The Sonoran Desert has two short rainy seasons and then it’s dry for months Couch’s spadefoot toads stay underground for most of the year and only come out when it rains
Some deserts are caused by more than one factor The Atacama is a coastal desert and experiences a rain shadow effect from the Andes Mountains Coastal deserts When air blows over a coast from a cold ocean the water vapor in the air condenses to form fog If the water droplets in this fog are too small to fall as rain they evaporate in the hot daytime sun This lack of moisture creates coastal deserts such as the Atacama Desert in Chile and the Namib Desert of South Africa Semi-arid deserts Semi-arid deserts are also known as cold winter deserts They have dry summers and cold winters with very little rain or snow Large mountain ranges often block precipitation from falling in these areas This is known as the rain shadow effect The Gobi Desert in central Asia and the Great Basin Desert in the USA are semi-arid deserts North America Atlantic Ocean Paci(cid:31)c Ocean South America Arctic Ocean Europe Africa Coastal desert Polar desert Semi-arid desert Subtropical desert Antarctica Asia Indian Ocean Paci(cid:31)c Ocean Australia This map shows the location of the four different types of desert found around the world 7
