Sahara

• Category: Desert Biomes
• Geographic Location: Northern Africa

• Summary: The largest hot desert in the world, the Sahara is home to diverse hardy species of plants and animals that have evolved and adapted to its rigors.

The Sahara Desert is the largest hot desert in the world. The Sahara stretches across eleven mostly large countries in northern Africa, from the Atlantic Ocean to the Red Sea, blanketing more than 3.5 million square miles (9.0 million square kilometers), more than one-fourth of the entire continent. The core desert biome encompasses about half that area, while the greater Sahara includes a full range of semiarid and related ecosystems.

The main desert consists of gravel plains, sand dunes, sand seas, salt flats, harshly weathered bare rock, a sprinkling of precious oases, and a topography ranging from the Atlas mountain range in its northwest to vast depressions in its interior. Sand dunes stand up to 590 feet (180 meters) in some areas; these are eclipsed in height by the mountains, among which volcanic Emi Koussi, in Chad, is tallest at 11,204 feet (3,415 meters). The lowest point is Qattara Depression, 436 feet (133 meters) below sea level, found amidst salt pans in northwestern Egypt. The world’s longest river, the Nile, flows south-to-north through the entire eastern side of the Sahara region; the mighty Niger defines its border along the southwest.

In this land of stark contrasts, the temperature range is no less extreme. A single day typically can sustain a high of over 100 degrees F (38 degrees C) and a low of 32 degrees F (0 degrees C). But the heat can climb much higher: one of the highest temperatures ever recorded on Earth occurred in the offshoot Libyan Desert in 1922, 136 degrees F (58 degrees C). Yet, there has been snowfall here, as well, although it is rare. One such celebrated event occurred in the sand dunes of southern Algeria in 1979. Between 2016 and 2021, snow was reported on the dunes in that same Algerian town four more times, the first reported sightings since 1979. While the snow did not last long, following the 2018 storm, some areas around the town reported that more than a foot of relatively rare snow had fallen.

Rainfall amounts to about 1 inch (2.5 centimeters) per year, averaged across the vast arid zone. Many thousands of years ago, due to low-pressure weather systems in the Mediterranean that were driven by the glaciation upon Europe, this region of northern Africa was treated to a fairly high precipitation regime, and the landscape was verdant. Upon glacial retreat, the northern expanse of the Sahara became steadily more arid, even while monsoon climate prevailed across its southern reaches. Once the monsoon pattern shifted away to the south and east—roughly 5,400 years ago—the desertification of today’s Sahara was complete.

Biota

Though several hundred plant species have been identified across the Sahara, the count is rather low for so vast an area. Arid-adapted plants, or xerophytes, predominate. Xerophytes tend to have very deep and well-developed root systems to tap groundwater; specialized internal tissues to store moisture; and reduced-size leaves often modified into spines and thorns, sometimes covered by a waxy layer—all to resist transpiration and promote water retention. Other prevalent plant types are the ephemeral varieties—those that sprout, grow, and regenerate only when the relatively rare moist periods occur in the desert. A third, fairly abundant, type is the halophyte, or salt-tolerant group.

In the Sahara, frequently seen trees, shrubs, and herbs include acacia, salt cedar, cypress, olive, fig, magaria tree, date palm, doum palm, oleander, thyme, African peyote cactus, and African welwitchsia. Grasses include lovegrass, or eragrostis; desert bunchgrass; and threeawn, or aristida. Those species with higher moisture requirements tend to cluster in transition areas around the fringes of the core desert, or at oases, where aquifer water has managed to percolate up fairly close to the surface. Among the fauna, large mammals are represented by the vulnerable dorcas gazelle, dama deer, dromedary camel, spotted hyena, and the critically endangered Sarahan cheetah. Smaller mammals include gerbil, kangaroo rat, Lybian striped weasel, slender mongoose, and cape hare.

The reptiles of the Sahara range from skinks, chameleons, and toads to horned vipers, desert crocodiles, and monitor lizards. Guinea fowl, Nubian bustard, pale crag martin, fan-tailed raven, black-throated fire finch, and African silverbill are among the distinctive avian species of the biome.

Human Interaction

The human population in the Sahara desert has been estimated to be between 2.5 million and 4 million, yielding one of the lowest population densities in the world. It is believed that the desert has been inhabited for the last six thousand years. The dominant ethnic groups and tribes include Berbers, Tuaregs, Toubou, Beja (Sahrawi), Zinghawa, Songhai, Kanuri, Fulani, Hausa, and Nubians. The main language spoken in the desert among the tribes is Arabic. Indeed, the name Sahara itself derives from the Arabic word for desert, which is sahra. This, in turn, is a form of the term asharu, meaning yellowish-red.

Today, the majority of the people who dwell here are nomadic pastoralists, moving from place to place with their herd animals, which are mainly sheep and camels. Except scattered oasis villages, a few crossroads settlements, mining towns, and cities around the fringes where extraction industries are based, the majority of the people are of this transient nature. Some people around the edges of the Sahara, however, practice agriculture grounded in irrigation from the fertile Nile River Valley, for instance. The potential also exists for drilling wells into some of the newly discovered aquifers that underlie various parts of the desert.

Deposits of iron ore in Algeria and Mauritania, copper in Mauritania, oil and gas in Algeria and Libya, and phosphates in Morocco and Western Sahara have fueled economies and led to population increases in those areas. Each development, of course, has also raised concerns about ecological damage and habitat disruption. Several trans-Saharan highway plans have been proposed, and some partly built, but these largely remain uncompleted or abandoned.

Global warming projections for the Sahara Desert biome are extremely divergent. Some records show, for instance, that climate change has already caused the Sahara to spread beyond some of its historical boundaries. In Sudan, rainfall has declined steadily for decades, as desert has encroached upon farmlands and grazing areas; increased scarcity of fertile soil and available water has fed into such conflicts as the warfare in the Darfur region of Sudan. In 2018, scientists publishing a study in the Journal of Climate found that the desert had expanded southward by 10 percent since 1920, extending more toward some of the tropical and agricultural regions of countries such as Chad and Sudan. The authors of the study cited both human impact and natural climate changes as causes.

Climate change is expected to have an effect on the Sahara’s notorious dust storms, one of which grew so large in 2020 it spread out across the Atlantic Ocean to North America. Scientists at the National Aeronautics and Space Administration (NASA) found that warmer ocean water temperatures and a hotter climate will actually work to shrink the dust storms over the course of the next century.

On the other hand, more recent studies point to increased rainfall and the spread of vegetation in previously barren areas of Chad, southwestern Egypt, and western Sudan. Specifically, new stands of acacia trees have been recorded in these areas. Researchers have posited this is due to the capacity of hotter air to hold more moisture, and thus to release more rain. A similar scenario may be playing out in parts of Moroccan-controlled Western Sahara, where pastoralists have reported an expansion of grazing lands fed by heavier rainfall.

In the 2020s, real estate developers and entrepreneurs increasingly explored the potential to develop parts of the Sahara. Efforts were made to open up land development opportunities through the use of renewable energy, water conservation methods, and sustainable agriculture practices. Such initiatives aimed to address the challenges posed by the harsh climate, limited water supply, and fragile ecosystems of the region. Proponents of development argued it would help the region's economy by increasing tourism and job creation.

Bibliography

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