The Sahara is the largest hot desert in the world and the third largest desert behind Antarctica and the Arctic, which are both cold deserts. The Sahara is one of Earth’s most hostile environments, covering 3.6 million square miles (9.4 million square kilometers), almost a third of the African continent, roughly the size of the United States. United States (including Alaska and Hawaii). The name of the desert comes from the Arabic word ṣaḥrāʾwhich means “desert”.

Geography

The Sahara is bordered by the Atlantic Ocean to the west, the Red Sea to the east, the Mediterranean Sea to the north and the Sahelian savannah to the south. The immense desert extends over 11 countries: Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and Tunisia.

The Sahara Desert has a variety of land features, but is most famous for the sand dune fields that are often depicted in movies. The dunes can reach nearly 183 meters high, but they only cover about 15% of the entire desert. Other topographic features include mountains, plateaus, sand and gravel plains, salt flats, basins and depressions. Mount Koussi, an extinct volcano in Chad, is the highest point in the Sahara at 11,204 feet (3,415 m), and the Qattara Depression in Egypt is the deepest point in Saraha, 436 feet (133 m) below the sea level.

Although water is scarce throughout the region, the Sahara contains two permanent rivers (the Nile and the Niger), at least 20 seasonal lakes and huge aquifers, which are the main sources of water in more than 90 large desert oases. Water management authorities once feared that the Sahara’s aquifers would soon dry up due to overexploitation, but a study published in the journal Geophysical Research Letters in 2013 found that “fossil” (non-renewable) aquifers ) were always fed by rain and runoff.

the fauna and the flora

Despite the harsh and arid conditions of the desert, several plants and animals inhabit the area. There are about 500 species of plants, 70 known species of mammals, 90 species of birds and 100 species of reptiles that live in the Sahara, as well as several species of spiders, scorpions and other small arthropods, according to the World Wildlife Fund.

Camels are one of the most emblematic animals of the Sahara. Large mammals are native to North America and finally crossed the Isthmus of Bering between 3 and 5 million years ago, according to a study published in the Research Journal of Agriculture and Environmental Management in 2015. Camels have were domesticated about 3,000 years ago on the southeastern Arabian Peninsula, to be used for transport in the desert, according to the University of Veterinary Medicine in Vienna.

Camels, also known as “desert ships,” are well adapted to the hot, arid environment, according to the San Diego Zoo. The humps on a camel’s back store fat, which can be used for energy and hydration between meals. Camels store energy so efficiently that they can go more than a week without water and several months without food.

Other residents of the Sahara include a variety of gazelles, addax (a type of antelope), cheetahs, caracals, desert foxes and wild dogs, according to the Sahara Conservation Fund.

Many species of reptiles also thrive in the desert environment, including several species of snakes, lizards, and even crocodiles in places where there is sufficient water.

Several species of arthropods also inhabit the Sahara, such as the dung beetle, beetle, “deathstalker” scorpions, and many types of ants.

Sahara plant species have adapted to arid conditions, with roots that reach deep underground to find buried water sources and thorn-like leaves that minimize moisture loss. The drier parts of the desert are completely devoid of vegetation, but the oasis areas, such as the Nile Valley, are home to a wide variety of plants, including olive trees, date palms, and various shrubs and grasses.

Weather

The Sahara alternates between dry, inhospitable desert and green, lush oasis roughly every 20,000 years, according to a study published in the journal Science Advances in 2019. The study authors examined marine sediments containing dust deposits from the Sahara of the past 240,000 years. The team found that the cycle between a dry Sahara and a green Sahara corresponded to slight changes in the tilt of the Earth’s axis, which also drives monsoon activity. When the Earth’s axis tilted the northern hemisphere a single degree closer to the sun (about 24.5 degrees instead of the current 23.5 degrees), it received more sunlight, which increased monsoon rains and, therefore, supported a verdant landscape in the Sahara.

Archaeologists have discovered prehistoric rock and cave paintings and other archaeological remains that shed light on life in the once green Sahara. Pieces of pottery suggest that around 7,000 years ago ancient shepherds herded cattle and harvested plants in what is now a barren desert.

But for about 2,000 years, the climate of the Sahara has been quite stable. Northeast winds dry out the air over the desert and push warm winds towards the equator. These winds can reach exceptional speeds and cause severe dust storms that can reduce local visibility to zero. Dust from the Sahara travels on the trade winds to the other end of the globe.

Rainfall in the Sahara ranges from zero to about 3 inches of rain per year, with some places not receiving rain for several years at a time. Sometimes snow falls at higher elevations. Daytime summer temperatures are often above 100 degrees Fahrenheit (38 degrees Celsius) and can drop to near-freezing temperatures at night.

The effect of climate change

The area of ​​the Sahara Desert has increased by almost 10% since 1920, according to a 2018 study published in the Journal of Climate. While all deserts, including the Sahara, increase in area during the dry season and decrease during the rainy season, human-caused climate changes in conjunction with natural climate cycles cause the Sahara Desert to grow larger and larger. shrinks less. The study authors estimated that about a third of the desert expansion was due to human-induced climate change.

One proposal to mitigate the effects of climate change is to install large-scale wind and solar farms in the Sahara. The farms would provide clean energy and reduce the amount of greenhouse gases entering the atmosphere, and could also promote increased rainfall in the surrounding area, according to a 2018 study published in the journal Science. Simulations have shown that in areas with wind farms there would be warmer temperatures, especially at night, caused by wind turbines bringing warm air to the surface from higher up in the atmosphere. The researchers also estimated that rainfall over wind farms would double on average, increasing vegetation by around 20%. Simulations of solar parks produced similar results.

The authors of the study predicted that a large-scale Saharan wind farm would produce about 3 terawatts of electric power, while a large-scale Saharan solar farm would produce about 79 terawatts, which is well above the 18 terawatts of electrical energy consumed in 2017. The extra energy could be spent on larger-scale projects, including increased agriculture and water desalination.

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