Hot Deserts

Characteristics of hot deserts

Characteristically, a desert is an area of the world that experiences very little precipitation, and, as a consequence, supports very little life relative to other areas. In other words, deserts boast very little biodiversity relative to other biomes.

Broadly speaking, there are two major types of deserts: cold deserts (sometimes called temperate deserts) and hot deserts. Both types of deserts experience very little rainfall, but the names can probably clue you into the biggest difference: hot deserts get very hot.

As we just mentioned, deserts in general feature very little biodiversity due to the lack of rainfall. Less water means less life can be supported. But hot deserts have less water and greater heat, making them particularly challenging for plants and animals.

Climate of hot deserts

In general, hot deserts typically experience less than 250mm of rain per year. That's, on average, only about 20mm of rain a month, though some months of the year may experience more rain than others. The general lack of moisture means the heat in a hot desert is usually a dry heat with very low humidity relative to other climates.

But the real challenge is the heat. A hot desert typically experiences daily highs around 30-35°C, but daily temperatures can reach 40°C or higher. Parts of hot deserts like the Sonoran Desert and Lut Desert have been recorded as being as hot as 80°C!

At night, though, the temperature in a hot desert may plummet all the way down to 0°C. This is because, with little vegetation around, there's nothing to retain any heat.

Hot deserts generally have two seasons: winter and summer. Temperatures are slightly cooler in the winter.

Distribution of hot deserts

The majority of hot deserts are found around the equator (0° latitude), in between the Tropic of Cancer (∼23.44° north latitude) and the Tropic of Capricorn (∼23.44° south latitude). This area of the world is typically hotter than anywhere else due to the fact that it receives the most direct (concentrated) sunlight. It is important to note that not all hot deserts are found around the equator.

Take a look at the map below, which shows the global distribution of hot deserts.

Fig. 1 - Hot deserts in red (BWh); cold deserts in pink (BWk)

If you've read our Tropical Rainforest explanation, you might be a bit confused – how can lush, green jungles be around the same latitude as dry, sandy deserts? How do hot deserts form, to begin with?

Facts about hot deserts

Latitude is not the only factor that determines climate. In the case of hot deserts, factors like physical geography and winds play a role, too. For example, a high mountain range may cut off an area from local rain patterns in a phenomenon known as the rain shadow effect. The rain shadow effect likely played a big role in the formation of the Colorado Desert, which is shielded from the Pacific Ocean by the Peninsular mountain ranges.

Fig. 2 - The rain shadow effect can cause the formation of deserts

Planet-wide prevailing wind patterns, known as either easterlies or westerlies depending on which way they are blowing, can divert storms and rain away from areas. The formation of the Sahara Desert in North Africa has been linked to weather and wind patterns caused by the Intertropical Convergence Zone, where southeast and northeast easterlies meet.

Hot deserts location

Let's review the locations of a few specific hot deserts.

The Sahara Desert is the single largest hot desert in the world. It spans the majority of North Africa. If you associate the phrase 'hot desert' with rolling sand dunes and roaming herds of camels, you're probably imagining the Sahara. Near the Sahara is the Arabian Desert, which encompasses virtually all of the Arabian Peninsula.

Hot deserts in the Americas include the Atacama Desert in Chile, the Mojave Desert in the United States, the Sonoran Desert (which straddles the US-Mexico border), and the Chihuahuan Desert in Mexico. The Atacama Desert is known for being particularly dry.

A huge swathe of Australia is covered in hot deserts. Combined, these deserts are called the Great Australian Desert. The Great Australian Desert is one of the major reasons that around 85% of Australians live along the continent's coastlines.

Soils in hot deserts

Desert soils tend to be very dry and lacking in nutrients. Some desert soils appear cracked, while others are little more than loose piles of endless grains of sand. Strong winds in sandy hot deserts can create sandstorms, where sand is blown around dangerously, burying everything.

Desert soils (sometimes called aridisols) are not all that great at supporting plant life. Desert soils, in general, do not mix well with water. When sudden rainstorms do happen in deserts, they may cause flash floods, as water may pool at the surface.

Plants in hot deserts

If you associate cacti with hot deserts, you might be surprised to learn that the overwhelming majority of cactus species are native to the Americas. That means that if you were to set foot in the Sahara Desert or the Great Australian Desert, cacti would be few and far between!

Cacti have developed a particularly efficient method to conserve water. Though they still photosynthesize during the day, most cacti save their respiratory processes for nighttime, allowing them to use less water than they would normally have to. This process is called crassulacean acid metabolism, or CAM photosynthesis.

The most instantly recognizable cactus is probably the saguaro (Carnegiea gigantea), though this tree-like cactus is endemic to just a small portion of the Sonoran Desert in North America.

Fig. 3 - The saguaro is probably the most iconic cactus species in the world

All cacti are succulents, a group of plants that are characterized by their thick leaves and stems. Succulents retain water. Aloe vera, endemic to the Arabian Desert, is a succulent.

Other plants in hot deserts include hardy desert scrub, shrubbery, trees, and flowering plants.

Animals in hot deserts

What animal do you most associate with hot deserts? Earlier, we mentioned camels. The dromedary camel (which has one hump) is endemic to the Sahara Desert and the Arabian Desert. Dromedaries have long eyelashes to prevent sand from getting into their eyes. Dromedaries can also go up to 15 days without drinking water. A popular misconception is that camels store water in their humps – in reality, camel humps are extra stores of fat that camels can draw upon when they're having a hard time finding plants to much on. Dromedary camels were domesticated by people living in North Africa and the Arabian Peninsula; feral dromedaries can be found in Australian deserts.

Fig. 4 - A caravan of dromedary camels in Egypt

Reptiles and insects are ectothermic, or cold-blooded, meaning they cannot regulate their own body heat and are dependent upon sunlight to warm them up. This actually makes them quite suited to hot deserts, though they usually need to seek shelter during the hottest part of the day to avoid overheating. Desert reptiles and insects include many different types of tortoises, snakes, lizards, scorpions, beetles, and tarantulas, like the thorny devil (Moloch horridus), the sidewinder (Crotalus cerastes), the desert tortoise (Gopherus agassizii), and the sacred scarab beetle (Scarabaeus sacer).

To avoid the daytime heat of hot deserts, many mammals and birds are either nocturnal, meaning they are active at night, or crepuscular, meaning they are active at twilight. This includes many different types of rodents, like kangaroo mice, cactus mice, and hamsters, as well as larger animals like owls, foxes, bobcats, and coyotes.