Why should we prevent land desertification? Land desertification is the result of comprehensive action of natural factors and human activities. Natural factors mainly refer to abnormal climatic conditions, especially severe drought conditions, which cause vegetation degradation and accelerate wind erosion and desertification. Man-made factors mainly refer to overgrazing, deforestation, grassland reclamation and continuous farming, resulting in vegetation destruction, bare surface and accelerated wind erosion or rain erosion. Worldwide, overgrazing and inappropriate dry farming are the main causes of desertification in arid and semi-arid areas. Similarly, poor water management in arid and semi-arid areas has caused large-scale land salinization, which is also a very serious problem. Judging from the composition of the impact of human activities on land degradation in the Asia-Pacific region, vegetation destruction accounts for 37%, overgrazing accounts for 33%, unsustainable agricultural cultivation accounts for 25%, and over-exploitation of infrastructure construction accounts for 5%. The situation in Africa is similar to that in Asia. Overgrazing, overgrazing and a large number of firewood villages are the main reasons for land desertification. The main effects of desertification are: the decline of land productivity, the subsequent reduction of agriculture and animal husbandry production, huge economic losses and a series of social consequences, and even a large number of ecological refugees in extremely serious cases. 1984 to 1985 During the great famine in Africa, at least 30 million people were in a state of extreme hunger, and100000 people became refugees. According to the estimation of 1997 United Nations Conference on Desertification, the loss of production capacity caused by desertification is close to $20 billion every year. In 1980, the United Nations Environment Programme further estimated the economic losses caused by the failure to prevent land degradation in drought, and estimated that the total losses in the next 20 years would be about 520 billion US dollars. 1992, the United Nations Environment Programme estimated that the annual economic loss caused by global land degradation was about $42.3 billion (calculated at the price of 1990). If no measures are taken to prevent land degradation in the next 20 years, the total loss will be as high as 850 billion US dollars. Comparing the losses of different continents, Asia suffered the most, followed by Africa, North America, Australia, South America and Europe. From the perspective of land types, the degraded area of grazing land is the largest, and the loss of irrigated land and rain-irrigated land is roughly the same. According to the comparison between the estimates made by 1980 and 1990, the global direct loss during1978-199/kloc-0 is about $300-600 billion. This does not include losses and indirect economic losses outside desertification areas. Types and Distribution of Desertification in China There are four types of desertification land in China: wind erosion desertification, water erosion desertification, freeze-thaw desertification and soil salinization. China's wind erosion and desertification land covers an area of 6.5438+0.607 million square kilometers, mainly distributed in arid and semi-arid areas, which is the largest and most widely distributed among all kinds of desertification land. Among them, the arid area is about 876 thousand square kilometers, which is generally distributed in the west of Langshan Mountain in Inner Mongolia. The Tengger Desert and the north of Longshou Mountain include the north of Hexi Corridor, the Qaidam Basin and its north, and the west of Tibet. The semi-arid area is about 492,000 square kilometers, which is generally distributed in the east and south of Langshan Mountain in Inner Mongolia, passing through Hangjinhouqi, Chengkou County and Wuhai City, and then running through the central and eastern Hexi Corridor to Subei Mongolian Autonomous County, showing a continuous large-scale distribution. How to prevent land desertification? Specific measures include: (1) implementing the grassland household contract system; (2) limiting the maximum carrying capacity of grassland, establishing grassland supervision system and prohibiting overgrazing; (3) Do a good job in the grass fence and plant trees next to it; (4) Changing the feeding mode and carrying out livestock house feeding or rotational grazing; (5) Strengthen grassland conservation and vigorously prevent and control grassland pests and rodents; (6) Take measures to restore grassland vitality. In the mountainous and hilly areas widely distributed in the western region, water and soil erosion caused by hydraulic power is more prominent, which leads to the decline of land quality and production potential. Therefore, it is necessary to strengthen the improvement of the mountain environment in the middle and upper reaches of the Yangtze River. Specific measures and methods include: (1) comprehensive planning and comprehensive management. (2) Reasonable adjustment of land use structure. (3) Management and monitoring of soil and water conservation. (4) It is an important measure to improve degraded sloping land and return farmland to forest and grassland. However, some farmers scattered in areas lacking basic living conditions, after receiving the grain money from returning farmland to forests, still rely on mountain areas to open up wasteland, cut down trees and dig grass. Form a vicious circle of "more cutting is more barren, more cutting is more". Therefore, the government should create conditions to gradually remove the poor people scattered in areas with particularly harsh living conditions and resettle them in areas suitable for survival and development, so as to fundamentally solve the problems of ecological protection and poverty alleviation for these people. At the same time, we should also pay close attention to the implementation of returning farmland to forests and grasslands. Biological measures refer to the protection and restoration of natural vegetation through the establishment of artificial vegetation, so as to finally achieve the purpose of preventing the harm of sandstorms, controlling and developing and utilizing desertified land. Practice shows that biological measures are the fundamental measures to prevent desertification. Mechanical and chemical measures are usually used as auxiliary measures for biological measures. The main biotechnological measures to combat desertification are to build windbreak and sand-fixing forests, farmland shelterbelts and protect and restore degraded vegetation. There are three specific ways, artificial afforestation, aerial seeding afforestation and sand sealing to promote afforestation.