If you are going for a day trip Sahara Desert In North Africa, you will have to bring a lot of water and a lot of sunscreen. However, if you plan to spend the night, it is best to bring a comfortable sleeping bag.
This is because once the sun goes down, the temperature of the Sahara Desert will drop sharply, from the average maximum temperature of 100 degrees Fahrenheit (38 degrees Celsius) during the day to the average minimum temperature of 25 degrees Fahrenheit (minus 4 degrees Celsius) at night. According to NASA.
So, why do such drastic temperature changes occur in arid deserts like the Sahara? How do native animals and plants cope with this extreme situation?
related: Will the Sahara Desert turn green again?
Damp heat
The cause of arid desert-arid area Cover about 35% The earth̵
Unlike a thermos, sand does not retain heat well. When the heat and light from the sun hit the sandy desert, the sand grains on the top of the desert will absorb and release the heat. According to a 2008 report from NASA’s Jet Propulsion Laboratory In Pasadena, California. During the day, the sun energy emitted by the sand overheats the air and causes the temperature to soar. However, at night, most of the heat in the sand will quickly dissipate into the air, and no sunlight will reheat it, making the sand and its surroundings colder than before.
However, this phenomenon alone does not explain the sharp drop in temperature. After all, when the sun sets on a tropical beach, you don’t need to wear winter clothes.
The main reason for the rapid temperature change is that the desert air is very dry.In arid deserts such as the Sahara and Sahara Atacama Desert In Chile, the humidity-the water vapor content in the air-is almost zero. Unlike sand, water has a large heat storage capacity.
The water vapor in the air pulls the heat close to the ground like a huge invisible blanket, preventing it from escaping into the atmosphere. According to the World Atlas. The air with high humidity also needs more energy to heat, which means that the energy is dissipated and the surrounding environment also takes more time. Therefore, the lack of humidity in the desert causes these dry places to heat up rapidly, but also to cool down rapidly.
Adapt to extreme temperatures
Despite these rapid temperature fluctuations, desert animals are very adaptable to extreme temperature changes in the desert.
Dale DeNardo, an environmental physiologist at Arizona State University, said: “For them, this is often a relatively small problem.” “The bigger challenge is to get enough food and water to survive.”
Reptiles are the most numerous and diverse animals in the desert. They are very adaptable to extreme temperature changes because they are cold-blooded or hot outside, which means they don’t need to spend energy to maintain a constant body temperature. In other words, reptiles can use this energy in other places, such as hunting. Many reptiles also benefit from it because they are small and can find dark corners during the day and warm rocks at night. DeNardo told Live Science: “There are many different places that can get warmer or cooler, especially when you are very young.”
related: How do lizards cool?
However, large warm-blooded or endothermic mammals such as camelIt is too large to avoid sunlight, and cannot let their body temperature drop. In contrast, camels survive by maintaining a constant body temperature in hot and cold conditions. DeNardo says they do this by applying a lot of heat insulation in the form of fat and thick fur, preventing them from gaining too much heat during the day and losing too much at night.
In contrast, desert birds use evaporative cooling (transferring heat from the body through water, such as human sweat and dog panting) in a variety of ways (some condors urinate on their legs to cool). But they have the ability to fly long distances between water sources or clear food, which means they don’t have to worry about saving water like other desert animals. Denado said: “I call it cheating because they didn’t really experience the limitations of the desert.”
On the other hand, plants are more susceptible to extreme temperatures. Denaldo said: “They face greater challenges because they refuse to move.” This is why iconic desert plants (such as cacti) have developed a series of defenses, such as spikes and toxins, to protect them. Precious water is protected from predators. However, freezing temperatures at night can be fatal to plants, because water freezes and swells in their tissues, which may cause irreversible damage. Therefore, plants only grow in areas where the temperature does not fall below freezing point for no more than a few hours per night at night.
climate change
Researchers are still figuring out how climate change Dinardo said this may affect dry areas and organisms, but “we will definitely see changes.” “For most deserts, we expect temperatures to increase by 3 to 4 degrees Fahrenheit on average. [1.7 to 2.2 C]. ”
However, studies have shown that “nights will get hotter and hotter, but this is not worse than warm days,” DeNardo pointed out.
Instead, the real problem is that climate change may affect the annual precipitation on which desert organisms depend. DeNardo said: “It will become less stable. You will have relatively wet years and relatively dry years.” “But even if most of them are wet enough, it only takes a really dry year to cause big problems. .”
Originally published in “Life Science”.
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