论荒漠化的型式问题——以西非萨赫勒地带为例

ON THE PATTERN OF DESERTIFICATION A CASE STUDY OF SAHEL ZONE, WEST AFRICA

荒漠化问题研究中，荒漠化型式（Ｐａｔｅｒｎ）问题是最重要的问题之一。它与对荒漠化本质的认识有关，与荒漠化防治的实践有极其密切的关系。该文以萨赫勒地带为例，讨论和分析了其荒漠化的过程（即过度放牧、滥施耕作、烧荒和火灾及过度樵采引起的荒漠化过程）问题，指出：荒漠化是由于人类不适当经济活动而在其内部生成的；从总体上讲，其荒漠化不是其北面撒哈拉沙漠的流沙和沙丘向南推进的结果。因此，为阻止荒漠化而在其北部边缘建造所谓“绿带”，不可能遏止其荒漠化的发展。只有加强管理，坚持适度利用和因地制宜地利用环境和资源的原则，防止人类的过度经济活动，才能有效地防治荒漠化。

esertification is one of the most serious environmental problems in the world and one of the global major problems established by the United Nations. And the matter of desertification pattern is one of the most important aspects in the study of desertification, because it has close relation to the understanding of the essence of desertification and the prevention of desertification. First of all, a new definition of the concept “desertification” is given in the paper. Then three questions are discussed or analysed. First, the situation of the desertification in Sahel is introduced, and a popular viewpoint about the desertification pattern is mentioned and discussed. According to the viewpoint it seems that the desertification is the result of advancing or creeping southwards of the Sahara north of Sahel. It is not correct and doesn't tally with the actual situation. Second, four mechanisms of the desertification in Sahel are put forward, and they are overgrazing, overcultivation, firing and overgathering of firewood. Third, based on the analysis of the four mechanisms mentioned above it is pointed out that the desertification is produced from the Sahel zone itself, basically not from the outside. Obviously, the results of the processes or mechanisms of desertification are the same, that is the formations of deserfication land patches. Ususally serious overgrazing will produce bare land patches in different sizes because it often take place around wells or other water source points and some pasturelands with good grass. Unsuitable cultivation always happens in some places with rich soil and moisture, leading to the formation of bare desertification land patches. Other desertification mechanisms have the same results. With the passage of time these desertification land patches in Sahel gradually increase and enlarge, finally merge together, and join the Sahara, and it looks as if the Sahara advanced southward. In fact the Sahara doesn't move on. Someone with that viewpoint considers that a greenbelt (shelter forests) should be built along the edge of the north part of Sahel to prevent desertification in it. As mentiond above the desertification take place in the zone itself, the greenbelt measure will not reach the goal.