世界上最大的沙漠－撒哈拉

　　Climate 　气候

　　The Sahara's climate consists of basically two sub-climates， a dry subtropical climate in the north and a dry tropical climate in the south. The dry tropical climate is generally characterized by mild， dry winters， a hot dry season just before the rainy season， and an annual temperature cycle. The dry subtropical climate， however， is characterized by annually high temperature ranges， cold winters， hot summers and two rainy seasons. There is a narrow strip in the western portion of the Sahara， along the coast， which generally has cool temperatures compared to the rest of the Sahara because of the influence of the cold Canary Current.　撒哈拉沙漠包含了2种气候，　一种是北部的干旱亚热带气候，令一种是南部的干旱热带气候。

　　Plant Life 　植物生活

　　The Sahara is sparsely covered with various types of vegetation ranging from grasses， shrubs， and trees in the highlands to halphytes， which are saline-tolerant plants found in saline depressions. One characteristic of the vegetation found in the Sahara is that these species must be able to adapt to unreliable precipitation and excessive heat. 草丛，灌木和树木都可以生长，这些树木的特点是能承受巨热和盐碱地带。

　　Animal Life 　动物生活

　　Some of the mammal species found within the Sahara are the gerbil， jerboa， Cape hare， the desert hedgehog， dorcas gazelle， dama deer， Nubian wild ， anubis baboon， spotted hyena， common jackal， sand fox， Libyan striped weasel， and the slender mongoose. The Sahara also contains over 300 species of migratory bird populations along with water and shore birds and various other types of birds. Some of the most common birds are ostriches， raptors， secretary birds， guinea fowl， Nubian bustards， desert eagle and barn owls， sand larks， pale crag martins， and brown-necked and fan-tailed ravens. 哺乳动物，鸟类都可以找到。

　　The People 人类

　　The Sahara Desert covers over 3.5 million square miles and has only 2.5 million inhabitants - roughly 1 person per square mile （0.4 sq km）- which is one of the lowest population densities on earth. Wherever abundant food and water sources occur， one will find relatively large masses of people and wildlife. On the whole， the Sahara is one of the harshest environments known to man. 　居住人口极少，大约每人占地0.4平方公里，是世界上最少的人口密度。

　　Many researchers have gone into the Sahara looking for clues as to how long ago humans began inhabiting the desert. According to archeologists， the Sahara was much more densely populated thousands of years ago when the desert's climate was not as harsh as it is today. Fossils， rock art， stone artifacts， bone harpoons， shells and many other items have been found in areas which today are considered too hot and dry to inhabit. This suggests that these areas were quite habitable thousands of years ago， but that the climate of the Sahara has since changed drastically. The artifacts found were located near remains of giraffe， elephant， buffalo， antelopes， rhinoceros， and warthog， as well as the remains of fish， crocodiles， hippopotamuses and other aquatic animals which suggests that thousands of years ago water was quite abundant in the Sahara. 很多研究者经常深入撒哈拉去寻找人类是多久以前就在沙漠中生活了。　据历史学家调查，在千方年前的撒哈拉，人口密度比现在要高，是因为那时的沙漠的条件没有现在那么险恶。

　　The majority of the people living in the Sahara Desert are nomads， which means that these people continuously move from region to region in search of better living conditions. It is believed that the first nomadic peoples came to this region after domestic animals were introduced to the Sahara 7，000 years ago. Researchers believe that sheep and goats were introduced to the Sahara region by the Caspain culture of northern Africa. 居住在沙漠里的大部分是游牧民，也就说他们不停的迁移，为了找到更适合生存的环境。

　　Evidence suggests that the Sahara accumulated diverse groups which quickly formed dense populations throughout the region. The majority of the groups lived separately， but depended on each other for trade. External trade developed gradually and the mobility of the nomads certainly contributed to the growing success of trade with other countries and continents. For example， Mauritania contained valuable copper resources and as a result， this copper was traded to the Bronze Age Civilizations of the Mediterranean. 这些游牧民族也靠和外界的较易生活。