【摘 要】
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Land degradation in drylands,or desertification,is used with many meanings: here it is treated as the result of excessive human utilization of land with respect to its ecological resistance and resili
【机 构】
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University of Maryland, USA
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Land degradation in drylands,or desertification,is used with many meanings: here it is treated as the result of excessive human utilization of land with respect to its ecological resistance and resilience,under stressful environmental conditions.Degradation occurs throughout the world’s drylands and affects many aspects of land surface processes: for example,crop and livestock production; erosion and siltation of waterways; changes in surface energy and water exchanges and releases of dust that affects regional and global climate; and inhibition of sustainable development with increasing environmental,social,and even political instability.Despite its significance,there are no objective methods for measurement or monitoring of the degree of degradation that are relevant to the scales at which governments can intervene,that is provincial-countrywide-regional-global. Only satellite remote sensing techniques can provide data that are consistent over large areas and time periods measured in decades.Techniques used include measurement of vegetation cover,productivity,exposed bare ground,dead vegetation,soil moisture.Emerging methods include hyperspectral reflectances and active remote sensing with lidar and radar.
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