Year: 2008
Type: dissertation
Abstract: Sahel is the southern fringe of the Sahara desert. It is an arid region with erratic precipitation. During the 1970s and 1980s Sahel was afflicted with severe droughts and famine disasters. Since the 1970s there has been a debate concerning the concept of land degradation and desertification in Sahel. Recent findings suggest a positive trend in Normalized Difference Vegetation Index (NDVI), estimated from remote sensed data, over parts of the Sahel between 1982 and 2003. Analysis of precipitation data suggest that the mean annual precipitation is increasing during the same period, but only partly explains the vegetation greening. In this paper anthropogenic activities that may influence the vegetation have been examine by literature studies. The population in Sahel has steady increased since the 1970s. The demand for food has forced the farmers to shorten the fallow-periods and extend there cultivation areas into the natural vegetation. It may result in more greenness and a higher NDVI because arable land may be greener than natural vegetation. In the long-term there is a risk that the greening will decrease if the nutrient loss isn’t supplement with sufficient amounts of fertilizers or manure. During the last decades the herders have become more settled, due to political decisions, resulting in an uneven distribution of the increasing cattle herds. Away from the villages, where the pasture pressure has been reduced, denser natural vegetation can be expected with higher NDVI then before. The erratic precipitation has forced the farmers to find other incomes outside the farm to secure their self-support. This could affect the greening different ways. If the incomes from sources outside the farm are invested in the farm it may result in greener vegetation and a higher NDVI. The result in this study proposes that anthropogenic activities do affect the greening, but it is still uncertain to what extent. More detailed data and studies are required to identify the cause or causes to the increasing greening observed from satellites.
Author: Annika Carlsson
Language: Swedish
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2183571261