Status and Trend of Desertification in Northern China
Zhu Zhenda (Institute of Desert Research, Academia Sinica, Lanzhou)
In Northern China, the area of desertification is about 334, 000 sq. km., of which, 176, 000 sq.km.has already been desertified and 158, 000 sq.km.is being threatened by latent dangers. In talking about the area which has already been desertified, 42.2% was caused by the spread of desertification on sandy steppe; 52.3% was resulted from the activation of fixed dunes and 5.5% was brought about by the encroachment of dunes. In consideration of the causations of desertification, 25.4% of the desertification is brought into the world by over-cultivation of steppe; 28.5% was produced by over-grazing; 31.8% was originated under the influence of the collection of fuelwoods; 9 %caused by misuse of Water resources and techgenic factors and only 5.5%by the encroachment of sand dunes under windforce. By analyzing the above-mentioned percentage, it can be seen that the anthropological effects are the principle factors to develop desertification under the conditions where the surface is composed of sandy texture and the climate is characterized by drought and frequent winds. Therefore, the change of land use types and rational utilization of resources are the two fundamental steps to stop the development of desertification. From the viewpoint of the developmental degree of desertification, it is classified as following percentage that 19.3% of the already- desertified lands belongs to the most severe desertified land) 34.7% belongs to the severe desertified land and the on-going desertified land occupies 46.0% of that. particularly, it is worth to mention that the development of desertification in the marginal area (transitional zone of agriculture and range-land)is mostly formed in 1950s and more cares should be paid to the issue. According to the developmental trend, desertified lands, on the basis of contrastive analysis of aerial photographs in late 1950s and late 1970s, increased 39, 000 sq.km., namely the annual increasement of desertific-cation in Northern china is 1560 sq.km..The enlargements of desertification are caused by both the reclamation of sandy steppe and opens of vegetated dunes and the activation of dune under the influence of fuelwood collection and over- grazing.