中国土地退化及其防治对策

Land degradation and its control strategies in China

人类活动导致的土地退化系指通过风蚀、水蚀、次生盐渍化和污染等一个或多个过程导致的土地生物或经济产量的下降或丧失。风蚀是中国干旱土地上的主要问题，风蚀导致的土地沙质荒漠化面积为３７．１万ｋｍ２，水蚀主要发生于丘陵及山区，已影响到１７９．６万ｋｍ２的中国土地，其中水蚀导致的退化土地面积为３７．８万ｋｍ２，受次生盐渍化影响退化的土地面积为６．３万ｋｍ２。中国４６万ｋｍ２或占耕地面积的４０％耕地缺Ｐ，３３万ｋｍ２或１／３的耕地缺Ｋ。人类活动是导致土地退化的主要原因。在中国北方，过度放牧导致的土地退化占３０．１％，过度农垦占２６．９％，过度樵采占３３．７％，水资源利用不当占９．６％，工矿交通建设导致的占０．７％。在中国南方，因滥伐导致的土地退化占３７％，陡坡开垦占３５％，不适当植树造林占１８％，工矿交通建设占１０％。该文讨论了土地退化成因和危害之后，介绍了建国４０年来中国土地退化防治成就，还提出了退化土地防治策略，如提高公众参与退化土地防治意识，强化立法和开展监测和环境建设等。

Human induced land degradation refers to decline or loss of biological or economic productivity resulting from a process or combination of processes, including displacement of soil material, terrain deformation and loss of nutrients and/or orgnic matter through wind erosion, water erosion, secondary salinization and pollution. Wind erosion is a major problem in the dry land of China and the area of sandy desertified land caused by wind erosion has reached 371000 km 2. Water erosion frequently occurs in hilly and mountainous areas where 1.79 million km 2 of water erosion have been observed and degraded land area affected by secondary salinization now covers 63000km 2 in China. Statistical data indicated that depletion of soil nutriution is a serious problem in China. Some 460000 km 2 of cultivated or 40 percent of the total cultivated land area is deficient in P, and 330,000km 2 of cultivated land or one third of nations total is deficient in K. Adverse human activities are recognized as a principal reason of land degradation. In northerm China 30.1% of land degradation caused by over grazing, 26.9% by over reclamation, 33.7% by over fuel collection, 9.6% by mis use of water resources, as well as 0.7% by industrial, mining and transportation construction. In southern China, 37% of land degradation caused by deforestation, 35% by slopeland reclamation, 18% by improper afforestation, and 10% by industrial, mining and transportation construction. Following the discussion of the causes and disasters of land degradation, this paper presents the achievements gained in prevention and control of land degradation in the past four decades. The several control strategies measures in combating land degradation such as prompting public awareness and peoples participation, strengthening formulating national laws and policies, carrying out projects on rehabilization and monitoring, are proposed by the end of this paper.