When you hear the word desert, the mind usually drifts towards sun, sand and dunes. But in truth, deserts are much more varied than you might imagine. They come in all shapes and sizes and vary a lot from one part of the world to another.

You will probably be surprised to learn that the largest desert in the world is actually Antarctica.

Deserts are much more than the desolate landscapes we often imagine them to be. They are biologically rich habitats with a wide range of animals and plants that have adapted to live there. Some deserts are among the last areas of true wilderness on the planet, but many people inhabit them: more than a billion people (one-sixth of the world’s population) actually live in desert regions.

Deserts cover more than a fifth of Earth’s land area and can be found on every continent – and only 20% of them are covered in sand.

So what makes a desert?

A place that receives less than 25 centimeters (or 10 inches) of rain per year is considered a desert. They are part of a larger type of regions called drylands, which are defined by water scarcity. Drylands can lose more moisture through evaporation than they gain through precipitation.

Despite common misconceptions, deserts can be both hot and cold. The Sahara is the largest hot desert in the world and can reach temperatures of up to 122 degrees Fahrenheit (50 degrees Celsius) during the day.

But deserts can also be cold, like those in Antarctica and the Arctic – which also happen to be the two largest deserts overall. Cold deserts don’t have to be freezing: the Gobi Desert in Asia is considered a cold desert because it is sometimes covered in snow and frost. However, the winds can cause dramatic temperature changes in the Gobi Desert, from -40°C (-40°F) in winter to 45°C (113°F) in summer. These rapid temperature changes not only occur seasonally, but can even take place on the same day.

The driest deserts in the world, such as the Atacama Desert in Chile, have areas that receive less than 0.08 inches (or two millimeters) of precipitation per year. These are such harsh environments that researchers have studied them to get a better idea of ​​life on Mars. But every few years there is a very rainy period called “super bloom”. The Atacama Desert is perhaps the oldest desert on the planet, being hyper-dry for over 3 million years.

The largest desert in the world

Purely in terms of size, the Antarctic Desert is the largest desert on the planet, measuring a total of 13.8 million square kilometers (or 5,500,000 square miles). Antarctica is not only the most isolated continent on Earth, but also the coldest. It is considered a desert because its annual rainfall is less than 51 millimeters (or two inches).

To put that into perspective, much of the Sahara Desert receives twice as much rain as Antarctica. Antarctic coastal regions receive more rain, but still average only 200 millimeters (or eight inches) per year. Unlike most desert regions, however, the rain does not penetrate the ground. Instead, the snow accumulates on itself.

Despite so little rain, Antarctica still receives massive windstorms. Much like sandstorms seen in hot deserts, high winds pick up snow and turn into blizzards. The storms can reach speeds of up to 320 km/h (200 mph) and are one of the reasons the continent is so cold.

The continent is covered by a permanent ice cap that contains 90% of the Earth’s fresh water and has an average thickness of 1.6 kilometers. Only 2% of Antarctica is not covered by ice, an area mainly located along the coasts where penguins, whales, birds, seals and other animals reside.

There are no permanent human residents in Antarctica, but between 1,000 and 5,000 researchers can be found at different times of the year at research stations across the continent. The largest is McMurdo Station, located at the tip of Ross Island and operated by the United States.

Antarctica can also get terribly cold. The coldest temperature ever recorded was taken at the Soviet Vostok station on the Antarctic plateau. It reached a historic low of -89.2°C (-129°F) on July 21, 1983 and was obtained using ground measurements. Satellite data indicated a temperature of around -93.2°C on August 10, 2010, but the reading has not been confirmed.

Other great deserts of the world

Curiously, the second largest desert in the world is also cold. The Arctic desert covers a total area of ​​approximately 13.7 million square kilometers (5.29 million square miles). The total amount of precipitation is less than 250 mm (10 inches), mostly in the form of snow.

The desert partially occupies parts of territories claimed or controlled by Canada, Denmark, Norway, Russia, Sweden and the United States. The average temperature in the Arctic desert is -20°C, reaching as low as -50°C in winter. In summer, the sun does not set for 60 days. Then, in winter, there are long periods of darkness.

The third largest desert in the world is the famous Sahara, which is also the largest hot desert in the world. It has a total area of ​​9.4 million square kilometers (or 3.3 million square miles). It occupies most of the land of North Africa, except for the Maghreb regions, the Atlas Mountains and the coastal region by the Mediterranean Sea.

Average annual rainfall varies from very low in the northern and southern fringes of the desert to almost non-existent in the central and eastern parts. Most of the Sahara receives less than 20 millimeters (or 0.79 inches). Temperatures are also quite intense in the Sahara, and can rise to over 50°C.

Located in Western Asia, the Arabian Desert is the fourth largest on Earth. It covers an area of ​​2.3 million square kilometers (or 900,000 square miles). It encompasses much of Yemen, the Persian Gulf, Oman, Jordan and Iraq. Its center, known as the empty quarters, forms the largest continuous body of sand in the world.

The climate of this region is very dry. Temperatures oscillate between steady and typically high heat on one side of the spectrum and seasonal nighttime frosts on the other. Annual rainfall averages about 100mm, but the driest areas receive only 30-40mm of rain per year.

Also in Asia, the Gobi Desert is known as the fifth largest desert in the world. It has a total area of ​​1.2 million square kilometers (or 500,000 square miles) and covers parts of northwest and northern China, as well as southern Mongolia. It is called the “rain shadow desert” because the Himalayan mountains block the rainfall from the desert. It is not a sandy desert, but rather bare, exposed rock.

Desertification and environmental challenges

A significant number of semi-arid regions of the world are turning into deserts at record speed through a process known as desertification. This is not caused by natural drought but rather by deforestation and the demands of human populations settling in semi-arid lands.

For example, in northern China, expanding urbanization, which has left land unprotected from wind erosion, and the accumulation of sediment from a surrounding desert have recently created a problem of desertification. . In response, the government built a so-called great green wall serve as a border against the desert.

But that’s not the only challenge deserts face. Species in existing deserts are threatened by a warmer world. Higher temperatures cause more wildfires which then alter desert landscapes, eliminating slow-growing trees and shrubs and replacing them with fast-growing grasses.

Scientists have warned that the iconic Joshua tree from California may not survive a warmer climate. If this is indeed the case, the effect would also be severe in other species such as the yucca moth, which lays its eggs in the flower of the Joshua tree – and the effects could ripple through the food chain. Many desert birds could also be affected by dehydration and may not be able to survive in hotter deserts.

Deserts are a natural part of our ecosystem, but as is often the case, human intervention alters natural cycles. This change is often much faster than natural change, rendering ecosystems unable to adapt over time.+