第1个回答 2024-04-05
The Sahara Desert, sprawling across much of North Africa, is recognized as the largest hot desert globally. Extending from north to south, its width ranges between 800 and 1,200 miles, while from east to west, it covers over 3,000 miles (4,800 km). The desert's vastness divides Africa into two distinct regions: that which lies above or is part of the Sahara, and the remainder located south of the desert. To the west, the Sahara borders the Atlantic Ocean, and to the east, it reaches the Red Sea. The northern boundary is defined by the Atlas Mountains and the Mediterranean Sea.
Approximately 25 percent of the Sahara's surface is covered by sand sheets and dunes, creating a landscape characterized by shifting sands and vast stretches of flat, sandy terrain.
The climate of the Sahara is predominantly arid, with the northern region experiencing a dry subtropical climate and the southern region a dry tropical climate. The dry tropical climate features mild, dry winters, a hot dry season preceding the rainy season, and a distinct annual temperature cycle. In contrast, the dry subtropical climate is marked by significant temperature ranges throughout the year, cold winters, hot summers, and two rainy seasons. A narrow coastal strip in the western Sahara enjoys cooler temperatures due to the influence of the cold Canary Current.
Vegetation in the Sahara is sparse and adapted to the harsh conditions. Plant life ranges from grasses, shrubs, and trees in the highlands to halophytes, salt-tolerant plants found in saline depressions. These species have evolved to withstand unpredictable rainfall and extreme heat.
The Sahara is home to a variety of animal species, including the gerbil, jerboa, Cape hare, desert hedgehog, dorcas gazelle, dama deer, Nubian wild ass, anubis baboon, spotted hyena, common jackal, sand fox, Libyan striped weasel, and slender mongoose. The desert also supports over 300 species of migratory birds, alongside water and shore birds, and other avian species. Common birds include ostriches, raptors, secretary birds, guinea fowl, Nubian bustards, desert eagle owls, sand larks, pale crag martins, and brown-necked and fan-tailed ravens.
Despite covering over 3.5 million square miles, the Sahara has a population of approximately 2.5 million, giving it one of the lowest population densities on Earth. Areas with access to food and water sources attract larger concentrations of both human and wildlife populations. The Sahara is renowned for its harsh environment, posing significant challenges to human habitation.
Archaeological evidence suggests that the Sahara was once a more densely populated region, with a milder climate thousands of years ago. Fossils, rock art, stone artifacts, bone harpoons, shells, and other remains indicate that certain areas, now too hot and dry to support life, were once habitable. These findings imply a significant shift in the Sahara's climate.
The Sahara's population consists largely of nomadic communities, constantly on the move in search of improved living conditions. It is thought that nomadic lifestyles emerged in the region following the introduction of domestic animals around 7,000 years ago. Sheep and goats are believed to have been introduced by the Caspian culture of northern Africa.
The Sahara has been home to diverse groups, which rapidly formed dense populations across the region. These groups lived separately but relied on each other for trade. Gradually, external trade developed, and the mobility of the nomads doubtless facilitated thriving trade networks with other countries and continents. For instance, Mauritania's valuable copper resources were traded with Bronze Age civilizations in the Mediterranean.