Agrometeorological aspects of agriculture and forestry in the arid zones

The arid zones of the world are all characterized by a large deficit of rainfall in relation to the potential evapotranspiration. Their distribution around the world is governed by the interaction of global atmospheric circulation patterns, the distribution of land and sea, and local topography. Countries that have substantial areas with arid conditions belong to very different groups in terms of resource availability, agricultural productivity, population density and wealth. Most are poorly endowed with good agricultural land. Water resources vary tremendously, both in terms of reserves and consumption. Agriculture is in most cases the main consumer of water. Most arid zone countries have high population growth, and rural population densities are generally much higher than overall population densities. They have a wide disparity in wealth. The arid zones have a surprising diversity of agroecological niches, with edaphic conditions that can deviate substantially from those of surrounding areas. These niches often have a higher biomass or agricultural productivity. At the same time they are vulnerable to natural processes such as primary salinization, wind and water erosion. Increasing pressure of human and livestock population make that these natural environmental stresses lead to accelerated degradation and depletion of soil and water resources. As they exploit the various agroecological niches, the production systems of the arid zones are equally diverse, and cover the full spectrum of land use intensification from pastoral or transhumant livestock systems to rainfed or irrigated cropping systems. These production systems show rapid change under the pressures of environmental degradation, increasing land and water shortage, and the needs of expanding populations. With the exception of irrigation management, the agrometeorological needs of the arid zones have been insufficiently addressed in the past. Perceptions of homogeneity, low agricultural potential, low population density and the logistical problems of providing maintenance and collecting data from remote stations are largely to blame for this situation. Agrometeorological research can have a positive impact on the productivity, resource-efficiency and environmental sustainability of the arid zones by supporting a better characterization of the agricultural environments. Research targeted towards data spatialization and integration of meteorological and remote sensing information will help to alleviate the handicap of sparse meteorological data networks. At the same time these networks will need to be improved through installation of automatic stations and by establishing new partnerships with land users. © 2000 Elsevier Science B.V. All rights reserved.