If you are taking a day trip to the Saara’s desert in North Africa, you will want to bring lots of water and plenty of sunscreen. But if you are planning to spend the night, it is best to bring a comfortable sleeping bag as well.
That’s because temperatures in the Sahara can plummet as soon as the sun goes down, from a maximum average of 100 degrees Fahrenheit (38 degrees Celsius) during the day to a minimum average of 25 degrees Fahrenheit (minus 4 degrees Celsius) at night, according to NASA.
So why does this dramatic temperature change happen in arid deserts like the Sahara? And how do native animals and plants cope with these wild extremes?
Related: Could the Sahara be green again?
Heat and humidity
The reason for arid deserts – dry regions covering about 35% from Earth to Earth – getting so hot and, consequently, so cold, is a combination of two key factors: sand and humidity.
Unlike a thermos, sand does not retain heat very well. When the heat and sunlight hit a sandy desert, the grains of sand in the top layer of the desert absorb and also release heat back into the air, according to a 2008 report by NASA’s Jet Propulsion Laboratory in Pasadena, California. During the day, the radiation of sand with the energy of the sun overheats the air and causes temperatures to rise. But at night, most of the sand’s heat quickly radiates into the air and there is no sunlight to reheat it, leaving the sand and its surroundings cooler than before.
However, this phenomenon alone does not explain such a drastic drop in temperature. After all, when the sun goes down on a tropical beach, you don’t have to wear a winter coat.
The main reason for the sudden change in temperature is that the desert air is extremely dry. In arid deserts like the Sahara and the Atacama Desert in Chile, humidity – the amount of water vapor in the air – is practically zero and, unlike sand, water has a great capacity to store heat.
The water vapor in the air retains heat close to the ground like a giant invisible blanket and prevents it from dissipating into the atmosphere, according to the World Atlas. High humidity air also requires more energy to heat, which means it also takes longer for this energy to dissipate and for the environment to cool. Therefore, the lack of humidity in deserts allows these arid places to heat up quickly, but also to cool down quickly.
Adapting to extreme temperatures
Despite these rapid temperature fluctuations, desert animals are well adapted to extreme desert temperature changes.
“It tends to be a relatively small problem for them,” said Dale DeNardo, an environmental physiologist at Arizona State University who specializes in desert animals. “The biggest challenge is getting enough food and water to survive.”
Reptiles, the most abundant and diverse animal group in the desert, are well adapted to extreme temperature variations because they are cold-blooded, or ectothermic, which means that they do not need to invest energy to maintain a constant body temperature. In other words, reptiles can use this energy elsewhere, such as hunting. Many reptiles also benefit from being small, which allows them to find shaded corners during the day or warmer rocks at night. “There are many different places to go to get hotter or colder, especially when you are little,” DeNardo told Live Science.
Related: How do lizards calm down?
However, large warm-blooded or endothermic mammals, such as camels, are too big to hide from the sun and cannot let body temperature drop. Instead, camels survive by maintaining a constant body temperature in hot and cold conditions. They do this because they have too much insulation in the form of thick and thick hair, which prevents them from gaining too much heat during the day and losing too much at night, DeNardo said.
In contrast, desert birds use evaporative cooling – where they use water to transfer heat away from their bodies, as humans sweat and dogs gasp – using a variety of different methods (some vultures urinate on their legs to cool) . But their ability to fly long distances between water sources or to search for food means that they don’t have to worry about water conservation as much as other desert animals. “I call it cheating because they don’t really experience the limitations of a desert,” said DeNardo.
Plants, on the other hand, are more vulnerable to extreme temperatures. “They face a much greater challenge because they cannot move,” said DeNardo. That’s why iconic desert plants, like cacti, have developed a series of defenses, such as thorns and toxins, to protect your precious water from predators. However, freezing temperatures at night can be fatal to plants because water freezes and expands within their tissues, which can cause irreversible damage. Therefore, plants grow only in areas where the air temperature does not drop below zero for more than a few hours a night, known as a freezeline.
Climate change
Researchers are still discovering how of Climate Change it can affect arid places and organisms, but “we will definitely see changes,” said DeNardo. “For most deserts, we are predicting an average temperature increase of 3 to 4 degrees Fahrenheit [1.7 to 2.2 C]. ”
However, research indicates that “the nights are going to be warmer, but this is not as bad as the hottest days,” noted DeNardo.
Instead, the real problem is that climate change can impact the amount of annual rainfall that desert creatures depend on. “It will become less consistent, you will have relatively wet years and relatively dry years,” said DeNardo. “But even if most are wet enough, it will only take a really dry year to cause major problems.”
Originally published on Live Science.