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Rh above. It restricts the water supply and thus limits human settlement, especially on the slopes of Anti-Lebanon.

Whatever rain-water does not soak through the calcareous layers flows into streams and rivers, which swell into torrents after every heavy downpour, but shrink in the drought of summer to mere trickles or disappear altogether. The rush of water down the highlands, with its concomitant processes of erosion and denudation, has resulted through the ages in rendering barren many once-flourishing tracts of land. The perseverance without major modification of ancient crops, the persistence of tillage methods, and the preservation through the ages of virtually the same seasonal dates for ploughing and harvesting militate against any theory of desiccation through climatic changes. The real causes of decline in land productivity have been the denudation of the hillsides by the running rain water and winds, the failure of certain springs, deforestation and over-grazing which have deprived the loose soil of roots to hold it together, neglect of irrigation works and their destruction by barbarian invaders or attacking nomads, and possibly exhaustion of the soil in some places.

Three contrasting zones of vegetation are found in the Syrian area, in which two distinct floral regions meet: that of the Mediterranean and that of the western Asian steppe-land. The position of Mount Lebanon introduces the complicating factor of altitude, making the transition from Mediterranean to continental influences unusually abrupt. Banana plantations, winter sports resorts and desert oases are therefore encountered within a mere sixty miles of the sea. But everywhere the contrast between the landscape in spring, when the foliage is at its best, and in summer, when the increased heat has burned up vegetation, is very striking.

The coastal plain and the lower levels of the western highlands have the ordinary vegetation of the Mediterranean littoral, characterized by evergreen shrubs and quickly flowering, strongly scented spring plants. The main Rh