Author(s): UNEP
Pages: 30-35
Year: 1992 Issue:  2
Journal: World Environment
Keyword:  土地退化; 土地沙漠化; 土壤退化; 气候变化; 循环波动; 土地状况; 部分土地; 退化土地; 土地使用; 沙漠边缘;
Abstract: Desertification is land degradation in arid,semi-arid and dry sub-humid areas (drylands) resulting mainly from adverse human impact.It is a widespread but discrete process of land degradation in space throughout the dry- ands,which differs significantly from the phenomenon of observed cyclic oscillations of vegetation productivity at desert fringes (“desert expansion or contraction”) revealed by satellite data and related to climate fluctuations.At present desertification directly affects about 3.6 billion hectares—70 per cent of the total drylands,or nearly one quarter of the total land area of the world;it also affects about one sixth of the world’s population .These figures exclude natural hyper-arid deserts. This assessment of the current global status of desertification and land degradation has shown that accurate data that would demonstrate with greater precision the degree and rate of desertification in various parts of the world are still lacking.This shortcoming calls for further research and studies to define the magnitude of the pro- blem in all regions and localities,as well as the exetnt to which human beings are responsible for the process.The present gaps in knowledge,however,do not provide any excuse for delaying action .The existing data sufficiently justify urgent and effective action to control ongoing land degradation in drylands.