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Desertification, the creation of desert-like conditions where none had existed before, is the result of the vagaries of weather and climate or the mismanagement of the land or, in most cases, some combination of both. Such ecological deterioration in the Sahel (sahel: 荒漠草原(西非) ) has been linked in several ways to the increased size of livestock herds. During the fifteen years preceding 1968, a period of extremely favorable rainfall, the pastoralists (牧(羊)人) moved into the marginal regions in the north with relatively large herds. However, with the onset of a series of dry years beginning at the end of the rainy season in 1967, the pastoral populations found themselves overtaxing very marginal rangelands, with the result that the nomads viewed themselves as victims of a natural disaster. The mistaken idea that drought is an unexpected event has often been used to excuse the fact that long-range planning has failed to take rainfall variability into account. People blame the climate for agricultural failures in semiarid regions and make it a scapegoat for faulty population and agricultural policies.
Deterioration and ultimately desertification in the Sahel and in other ecosystems can be combated only if an ecologically realistic carrying capacity for the rangelands is determined. Although there appears to be widespread agreement that such a determination would be significant, there has been little agreement on how to make operational the concept of carrying capacity, defined as the amount of grazing stock that the pasture can support without deterioration of either the pasture or the stock. Should the carrying capacity (carrying capacity:承载能力) be geared to the best, the average, or the poorest years? Which combination of statistical measures would be most meaningful for the planning of long-term development of rangelands? On which variables should such an assessment be based, vegetation, rainfall, soil, ground and surface water, or managerial capabilities? Such inconclusiveness within the scientific community, while understandable, creates confusion for the land managers, who often decide to take no action or who decide that all scientific suggestions are of equal weight and, therefore, indiscriminately choose any one of those suggested. Given the downward spiral of land deterioration, it becomes essential that an ecologically acceptable carrying capacity be established and enforced.
It will also be crucial that land managers know what statistical and quasi-statistical measures actually mean: no single number can adequately describe the climate regime of an arid or semiarid region. Land managers must supplement such terms as the “mean” with more informative statistical measures to characterize adequately the variability of the climate. The understanding of this high degree of variability will serve to remove one of the major obstacles to resolving the perennial problems of the Sahel and of other arid or semiarid regions.
1. The author is primarily concerned with
(A) criticizing a social attitude
(B) suggesting an approach to solving a problem
(C) explaining the mechanics of a process C===B？？
(D) defending the theories of ecological scientists（B）
(E) establishing criteria for an experiment
2. According to the passage, which of the following contributed to the desertification of the Sahel?（应该是D呀）
I. The size of the livestock herds grazing on the land
II. The quality of the land in the Sahel
III. The amount of rainfall after 1967
(A) I only
(B) II only
(C) III only
(D) I and III only D===E==那里有说到II？（E）
(E) I, II, and III
第一题，任凭怎么看，看不出答案为什么是suggesting an approach to solving a problem。
第二题，看不到，找不到哪里说了II。。。。
哪位出手帮帮忙？谢过 | 
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发表于 2005-8-7 01:26:00
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