Contenu du sommaire

On the Distinctive Character of the Saharan Mountains. In presenting the varied contributions which make up this book, the author attempts to bring out the distinctive character of the Saharan mountains. After showing that in spite of their topography they in fact have few aspects in common with other mountains (poorly developed morpho- climatic and biogeographical zoning), he identifies three distinctive features of the physical environment : first, the mountain- oases which have acted both as refuges for species driven out of the lowlands and as a bridge for the migrations of flora; they constitute a museum of fossil forms (slopes, quaternary terraces, etc.) ; second, the hybrid mountains, enjoying a wide variety of flora on account of their rather special situation in an area where the Mediterranean, Ethiopian and Sudanese regions come together ; third, they constitute a break between the mountains of the wet tropical zone and those of the Mediterranean zone, the water deficit of the air and soils acting as the perfect limiting factor. The mountains also constitute, and have done since prehistoric times, poles of human activity on account of their water resources. Despite the decline in caravan traffic, the potential for development still exists from a pastoral and agricultural standpoint as well as in the field of tourism. However, increasing human populations are also putting fragile environments at a greater risk of degradation. From a physical as well as human point of view, the mountains of the Sahara constitute a sort of landmark along the meridional axes linking the Mediterranean and tropical worlds. Situated at the bridging point between these two areas, in the middle of vast expanses of plain and desert, they have played and continue to play a most distinctive role.