The Sahara Desert, according to the World Wide Fund for Nature (WWF), includes the extremely dry center of the Sahara between latitudes 18° N and 30° N. This area is one of several desert and dry shrubland regions that cover the northern part of the African continent.

Setting

The Sahara Desert is the world's largest hot, non-polar desert and is located in North Africa. It stretches from the Atlantic Ocean in the west to the Red Sea in the east, and from the Mediterranean Sea in the north to the Sahel savanna in the south. The desert includes several areas with different environments. The Sahara Desert ecoregion covers an area of 4,619,260 km (1,783,510 sq mi) in the extremely dry center of the Sahara. This region is surrounded by areas with more rainfall and more plant life.

To the north and west of the Sahara Desert ecoregion lies the North Saharan steppe and woodlands. This area receives more regular winter rainfall than the Sahara Desert ecoregion. To the south of the Sahara Desert ecoregion is the South Saharan steppe and woodlands, which lies between the Sahara Desert and the Sahel grasslands. This region gets most of its yearly rainfall during the summer. The Red Sea coastal desert is found along the coast between the Sahara Desert and the Red Sea. The western part of this area is called El Djouf, located on the border of Mauritania and Mali.

Some mountains rise above the desert and receive more rainfall and cooler temperatures. These Saharan mountains are home to two distinct ecoregions: the West Saharan montane xeric woodlands in the Ahaggar, Tassili n'Ajjer, Aïr, and other ranges in the western and central Sahara, and the Tibesti–Jebel Uweinat montane xeric woodlands in the Tibesti and Jebel Uweinat ranges of the eastern Sahara.

The surface of the desert includes large areas of sand dunes (erg), stone plateaus (hamadas), gravel plains (reg), dry valleys (wadis), and salt flats. The only permanent river that crosses the ecoregion is the Nile River, which begins in East Africa and flows northward into the Mediterranean Sea. Some areas have large underground water sources, creating oases, while other regions have very little water.

The Sahara Desert has a hot desert climate (Köppen classification BWh). It is one of the driest and hottest places on Earth, with average temperatures sometimes over 30°C (86°F). In summer, average high temperatures often exceed 40°C (104°F) for months, and can reach as high as 47°C (117°F). In desert mountains such as the Tibesti in Libya or the Hoggar in Algeria, summer temperatures are slightly cooler due to high elevation, ranging between 35 and 42°C (95 and 108°F) at 1,000 to 1,500 meters (3,300 to 4,900 feet). Daily temperature changes can be extreme, with swings from 37.5°C (100°F) to −0.5°C (31°F). Typical daily changes range between 15 and 20°C (27 and 36°F).

Rainfall in the Sahara is very low, with most of the desert receiving less than 100 millimeters (3.9 inches) of rain each year. The northernmost and southernmost edges, as well as the highest desert mountains, receive slightly more rain. More than half of the desert is hyper-arid, with less than 50 millimeters (2.0 inches) of rain annually, and some years may have no rain at all. The southern part of the Sahara, near the Sahel region, gets most of its yearly rainfall during the summer months when the Intertropical Convergence Zone moves north. Wind and sandstorms often occur in early spring. People living in the area protect themselves from the heat, sun, dry air, and dusty winds by covering their heads, such as the cheche garment worn by the Tuareg.

History and conservation

The Sahara was one of the first places in Africa where people farmed. About 5,000 years ago, the area was not as dry as it is now, and the plants there might have looked like those in a savanna. Some animals that lived there long ago can be seen in stone carvings. However, around 3000 BC, the area started to become very dry, and it became more like the Sahara we know today.

The Sahara has mostly stayed the same over time. The most harm to the environment happens in places where there is water, such as oases with underground water sources or along the edges of the desert where some rain falls each year. In these areas, animals like addaxes, scimitar-horned oryxes, and bustards are hunted too much for their meat. Only one area in the Sahara is protected for conservation: the Zellaf Nature Reserve in Libya.

Ecoregion delineation

In 2001, WWF created Terrestrial Ecoregions of the World (TEOW), a system to divide Earth's land areas based on their plant and animal life. This system split the Sahara desert into several ecoregions. The Sahara desert ecoregion included the very dry center of the Sahara, while the more humid mountain areas and the southern, northern, eastern, and western parts of the Sahara were classified as separate ecoregions.

In 2017, the creators of the 2001 system updated the ecoregion map for the Sahara. Two new ecoregions, West Sahara desert and East Sahara desert, were added to the very dry center. The transitional North Saharan steppe and woodlands and South Saharan steppe and woodlands ecoregions were expanded toward the central Sahara. The South Saharan steppe and woodlands ecoregion was renamed South Sahara desert.