If you are taking a day trip to the Sahara Desert in North Africa, you are going to require to bring tons of water & plenty of sunscreen. But if you are planning to stay the night, then you better-bring a snug sleeping bag, too.
That is because the temperatures in the Sahara can plummet once the sun sets, at an average high of 100 degrees Fahrenheit (38 degrees Celsius) during the day, and at an average low of 25 degrees Fahrenheit (minus 4 degrees Celsius) during the night, consistent with NASA.
Why does this dramatic temperature shift happen in arid deserts like Sahara? and how do native animals & plants deal with such wild extremes?
Heat and humidity
The reason that arid deserts, dry regions covering about 35% of Earth’s land, get too hot, & subsequently too cold, is a combination of 2 key factors: sand & humidity.
Unlike a thermos, sand does not retain heat very well. When heat & light from the sun hit a sandy desert, sand grains in the desert’s top-layer absorb and also release heat back to the air, consistent with a 2008 report from NASA’s Jet Propulsion Laboratory in Pasadena, California.
During the day, sand’s radiation of the sun’s energy superheats the air & causes temperatures to soar. But at night, most of the heat in the sand quickly radiates into the air & there’s no sunlight to reheat it, leaving the sand & its surroundings colder than before.
However, this phenomenon alone does not account for such a drastic drop-in temperature. After all, when the sun goes down on a tropical beach, you do not need to don a winter coat.
The main reason for the stark temperature change: desert air is extremely dry.
In arid deserts like Sahara & Atacama Desert in Chile, the humidity, the quantity of water vapour in the air, is practically zero and unlike sand, water features a huge capacity to store heat.
Air with high humidity also need more energy to heat-up, meaning, it also takes more time for that energy to dissipate & for the surroundings to cool-down. Therefore, a lack of humidity in deserts allows these arid places to quickly heat-up but also rapidly cool.
Adapting to extreme temperatures
Despite these rapid-temperature swings, desert animals are well adapted for the desert extreme temperature changes.
“It tends to be a relatively–small problem for them,” said Dale DeNardo, an environmental physiologist at the Arizona State University who specializes in desert animals. “The bigger challenge is getting enough food & water to survive.”
Reptiles, the most abundant & diverse animal group in the desert, are well adapted to extreme temperature variation because they’re cold blooded or ectothermic, it means that they don’t need to invest energy in maintaining a constant body-temperature.
In other words, reptiles can use this-energy elsewhere, like hunting. Many reptiles also advantaged of being small, which allows-them to find-out shady nooks during the day or warmer rocks in the night.
“There is a lot of different places to go to be warmer or cooler, especially when you are small,” DeNardo said.
However, large warm blooded or endothermic mammals like camels, are too-big to hide away from the sun & cannot let their body temperature drop.
Rather, camels survive-by maintaining a constant body temperature in both hot & cold conditions. They do-this by having some insulation in the sort off at & thick fur, which prevents them from gaining too-much heat during the day & 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 just like how humans sweat & dogs pant, through a variety of methods (some vultures urinate on their legs to cool-down).
But their ability to fly long distances between water sources or to scavenge food, means they do not need to worry as much about conserving water like other desert animals.
“I call it cheating, because they do not really experience the limitations of a desert,” DeNardo said.
On the other hand, plants are more vulnerable to extreme temperatures.
“They face a much bigger challenge, because they do not get to move,” DeNardo said.
That’s why iconic desert plants, like cactuses, have developed a variety of defenses, like spikes & toxins, to-protect their precious water from predators.
However, freezing temperatures at night can-be deadly for plants, because water freezes & expands within their tissues, which may cause irreversible damage.
Therefore, plants grow only in areas, where the air temperature doesn’t fall below freezing for more than a couple of hours each night, called as the freezeline.
Researchers are still figuring-out how climate change can affect arid places & organisms, but “we are definitely going-to see changes,” DeNardo said. “For most deserts, we’re an average rise in temperature of three to four degrees Fahrenheit [1.7 to 2.2 C].”
However, research indicates that “Nights are going-to be warmer, but that is not as bad as warmer days,” DeNardo noted.
Instead, the real problem is that climate change can impact the quantity of annual precipitation that desert creatures rely-on.
“It’ll become less consistent, you’ll have relatively wet years & relatively dry years,” DeNardo said. “But even if, most are wet enough, it’ll only take one really dry year to cause big problems.”