In general, the few Algerian rivers flow into the Mediterranean and are short; their course runs almost exclusively in the Maghreb area. The longest is the Chélif, while other courses of some importance are the Soummam and the Oued el-Kébir. The other river valleys of Algeria are dry (uidian); occasional but violent downpours can invade empty river beds or dangerously swell existing streams. The Chott plateau is characterized by closed endorheic basins; the waters that feed them come from rivers of the Saharan Atlas and give life to salt lakes (Chott Melrhir); on the southern side of the Atlas, on the other hand, several piedmont oases have been created. The desert bears traces of a fossil hydrographic network, evidence of a much more humid climate than the present one, but these ancient beds are home to waters only exceptionally, which evaporate after a few days.
The Berber element represents the ethnic substratum of Algeria; however, it has undergone profound transformations following Arab penetration, which has not only changed the human type but has above all “cultured” the country in an Islamic sense; in fact, at the beginning of the century. XXI, the population is made up of 74% Arabs and only 26% Berbers. The Arab penetration began in fact already in the century. VII and manifested itself massively in the century. XI with the arrival of the nomadic tribes of the Banū Hilāl, which led to a degradation of the ancient but wise Berber agriculture (there are however areas of refuge and conservation, especially in Kabylia and Aurès) spreading nomadic pastoralism, still widely practiced today. In the Sahara the oldest population seems to be represented by the black element; in prehistoric times, however, there were white populations: such were the fabulous Garamanti, of which traces are preserved almost until the beginning of the historical era. But at the time of the Roman penetration there was the displacement of Berber elements from the Atlas, with occupation of the oases (as is the case of the Mzabites) and transition to semi-nomadism (Tuaregh dell’Ahaggar); later also Arab nomadic groups settled in the Sahara. Most of the population lives today in the Tell, especially in the eastern section (the area of Algiers is the most densely packed area of the country).
According to ejinhua, the average population density, which is 17.88 residents / km², therefore has little significance because in reality the country is – taking into account the possibility of settlement limited to the Tell alone – overpopulated. In fact, the population, which at the end of the nineteenth century was 3 million residents and 4 million at the beginning of the century. XX, it was now over 40 million according to the 2018 estimate. In addition, the residents of urban centers have increased exponentially, so much so that in the early 2000s they are almost two thirds of the entire population. Urbanism, among other things, has no ancient traditions here: the first centers to develop were the ports, where commercial activity has been strengthened since the time of the Arab invasion, and some places in the interior of the Tell for the attraction they exercised on the surrounding agricultural areas: this is the case of Mostaganem, of Oran, of Algiers itself, of Béjaïa, of Annaba. All these cities had a great increase under French domination, but among them Algiers prevailed, which became the capital and control center of the whole country, and Oran, a typically European city, which also carries out port functions with respect to eastern Morocco; Annaba and Béjaïa received impetus as Saharan oil outlets. Further inland are some cities with mainly local commercial and administrative functions (Tlemcen, Sidi-Bel-Abbès, Chlef, Sétif) while Constantina is an important connecting node on the roads that link the Tell to the rest of the country. The centers of the highlands are less developed, with the exception of Batna, located on the railway to Biskra and the Saharan oases; some of these welcome populated centers such as Touggourt, Ghardaïa, El-Oued, Béchar.
Although the country has been subjected to deforestation for centuries to make room for grazing lands, the vegetation still preserves, in the Tellian and Saharan Atlas, strips of Mediterranean forests with cedars and oaks. Moving towards the region of the Chott plateaus, the vegetation begins to become scarce, giving rise to shrub-like formations; to finally get to Saharan Algeria, where the particularly arid climate allows the growth of a few very resistant plants, such as acacia, jojobaand the palm groves of the oases, in which, however, the crops have introduced fruit trees and vegetables. The scarce vegetation of the territory also has consequences on the fauna, which is present in limited numbers. Among the main species of animal life we find: the jackal, the hyena, the vulture, the antelope, the gazelle and numerous reptiles such as snakes and scorpions. In terms of environmental protection, Algeria is among the most advanced nations in the Maghreb. For some time now the country has given birth to a series of laws aimed at regulating the safeguarding of the natural heritage. The protected areas cover 5% of the territory and also include 11 national parks and an area declared a World Heritage Site by UNESCO: Tassili n’Ajjer (1982).