|Freshwater Resources in Arid Lands (UNU, 1997, 94 p.)|
|2: Negev: land, water, and civilization in a desert environment|
In antiquity the desert was regarded as a world unto itself, an extraterritorial realm separate from and additional to the other two known realms - the seas and the habitable rain-fed lands. The settled and "civilized" residents of the latter viewed the nomadic and "wild" people of the desert with fear and hostility, perceiving them to be a threat to civilization - as, indeed, they often were. The desert itself was held in awe as a place of terror, a largely useless and dangerous domain. One ventured into its mysterious vastness only at great risk. The desert's forbidding character has also been a challenge: a defiance of civilized mankind's self-proclaimed mastery of the earth; a barrier to human expansion, to progress, to economic development; a fortress holding out against colonization, against life itself.
But just what do we mean by the term desert? In what sense does it differ from what is commonly called an arid zone? Aridity in general is an imbalance between the demand for water and its supply, the supply being too scarce to meet the demand. Obviously, there can be different degrees of aridity. Such are the vagaries of climate that even so-called humid regions can experience occasional drought and even prolonged dry spells, though a humid region, by definition, is one in which annual precipitation is generally sufficient to sustain crop plants and, at times, may even be excessive. A semi-arid region is one in which precipitation is sufficient in most seasons but in which droughts (causing crop failure) occur frequently enough to make rain-fed farming a somewhat hazardous venture. An arid zone is one in which rain-fed farming is marginal successful in a few years but so frequently unsuccessful as to make the practice of rain-fed farming a highly insecure venture.
In arid regions, ironically, the crop plants' requirements for water are greatest just where the supplies by natural precipitation are the least. In such regions, therefore, the scales are weighted heavily against agriculture from the outset. The imbalance must be rectified by augmentation of water supply (i.e. irrigation), whenever possible, and by strict water conservation at all times. Despite the ever-present hazard of drought, farming populations can and do exist there, however precarious their economy. Extensive grazing - in addition to crop production and, occasionally, in preference to it - becomes a major form of land use in such areas.
The situation is fundamentally different in real desert areas, which are extremely arid. Here, even the precipitation in an average year - let alone in a drought - is definitely insufficient to sustain agricultural crops, so regular rain-fed farming is impossible. Hence, the biblical definition of the desert as "the land unsown." Even extensive grazing is marginal or submarginal. For humans to subsist in a desert without having to import most of their vital requirements, they must devise ingenious stratagems to obtain supplementary supplies of water, either by wresting the precious fluid from underground aquifers, if available, or by collecting it off the slopes of barren ground during brief episodes of rainfall, or by conveying it from another region. Only by such means can agriculture become possible, and then only on a fraction of the land area.