关键词: 联合国, 公约, 荒漠, 荒漠化土地, 范畴

Abstract: According to the definition in the UN Convention to combat desertification, desertification means land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors which including climatic variation and human activities. For a long time, scientists in China have different opinions on whether desert is desertified land. The formative processes of desert went gradually, and was not the reason of geologic motion directly produced. The geologic process resulted in dry climate, with which the land experinced strong physical weathering and salt accumulation, gradually lacked vegetation and evolved into desert. Meanwhile, it can't recognized that human activity has its function in the desert formation, although the beginning of mankind activity is remote. Therefore, there is no doubt that desert is resulted from various factors including climate change, human activity etc.. Desert is a type of land with the severest desertification degree, and should belong to the scope of desertified land. Desertification is a process, and desert is the final result of a positive course of desertification. In desert ecosystem, vegetation and environment stay stable relatively. while, the land system being in desertification processes is a fragile ecological system, in which positive and negative desertification processes happen alternatively. The tendency of the system evolution exists two opposite directionsdesert and oasis. The present land system is only a time-space point in very long land system evolution. Probably it has undergone for many times of recycling in steppe-farmland-steppe. Thus it is important to definite the degree of land degradation. But zero level is hard to be measured. In the light of present condition, it is difficult not only in all country, but also in a region to realize a unite zero level. Desert ecological system is relatively stable, although internal positive and negative process exist also. If desert is regarded as the initial level for comparison, the degree of land desertification could be determined with the evaluating method of "negative first and positive second", the desertification degree for most lands can be judged.

Key words: UN, Convention, Desert, Desertified land, Scope