Land-use influences on Sudanian landscape-scale vegetation change Burkina Faso, West Africa


Jeremy Fisher, John Mustard, Patrice Sanou (collaborator, Burkina Faso)and Silga Ousamane (collaborator, Burkina Faso)


Burkina Faso, West Africa experiences a strong precipitation gradient from the north (550 mm/yr) to the south (1200 mm/yr). Subsequently, Burkina Faso straddles two major types of traditional land uses, pastoralists (herders) in the northern desert margin and agriculturalists in south. These groups overlap in central Burkina Faso and utilize a variety of traditional mutually beneficial techniques to enhance fertility and maximize herd and crop yield. Increased population growth and increased climate variability (including longer droughts) were perceived to have pushed a formerly sustainable practice into a driver of land degradation. With the support of international donors and NGOs, local governments created land management areas (LMA) to combat the loss of soil fertility, less dense vegetation cover, and increased erosion. We hypothesize that by observing long term (decadal) trends at carefully controlled LMAs, we can begin to assess the various divers of change and degradation in Sudanian West Africa.

The Nouhao Valley, Boulgou Department of Burkina Faso, West Africa is one such LMA in SE Burkina Faso. In the 1960s, and epidemic of Onchocerciasis (River Blindness) forced the local populations in S. Burkina Faso to abandon river valleys, including the Nouhao. By the early 1980s, international efforts to reduce the River Blindness vector had succeeded in making the lands habitable again, and the Burkinabe government quickly worked to re-settle the areas. In Nouhao, the valley was divided into an exclusively pastoral (grazing) river valley and an agricultural buffer, surrounded by status quo mixed use lands.
We are utilizing five Landsat scenes from 1984, 1989, 1999, 2001, and 2002 to assess sub-pixel changes in land cover (vegetation cover, eroded surfaces, agriculture) and long time series AVHRR to provide a context of regional and local broad vegetation changes. Evidence suggests that since the separation of these land-use zones, vegetation in the pastoral zone has increased significantly. This suggests that grazing pressure and a stringent non-brush fire policy favors perennial shrubs over grasses, leading to an increase in greenness (palatable or not) in riparian areas and open savanna. We hypothesize that mixed land use, and seasonal low-level burns might be critical in maintaining recognized African savanna.

 

The Nouhao Valley LMA is in SE Burkina Faso. The exterior, closely controlled agricultural zone surronds the river basin pastoral zone

Detail of Tenkodogo (top left), and agricultural and pastoral zones. Zones have been color enhanced for clarity

Cotton fields in the agricultural zone

 

Burkinabe pastoralists

Ecology and Evolutionary Biology | Environmental Change Initiative | Environmental Studies | Geological Sciences | Marine Biological Laboratory | Watson Institute

Last updated 10/20/04

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