Dynamique de l'occupation du sol dans le département des collines au Bénin : essai de modélisation et impact sur l'utilisation des bas-fonds

The current research deals with the land use and land cover changes in the department of Collines in
Benin and its impact on inland valleys exploitation. The main objective of this exercise is to assess the
spatio-temporal dynamics that affects this department, dynamics caused by the various practices
observed in matter ofresources exploitation, and to analyze the corollaries especially as far as the inland
valleys use is concemed.
On the basis of Remote Sensing tools and Geographical Information System (GIS), the changes of the
land use and land cover between 1978 and 1998, revealed that only 22.3 % of all the studied area is
stable, 59.4 % is in regression and 18.3 % extends. Spaces in regression concem the woody savannah
and the gallery forest.
The modelling of land use and land cover change, usjng Cellular Automata in the base of Markov
processes, leads to the setting up of a transition matrix that reveals that most of the land use and land
cover units has changed extensively toward crops and fallows in 1998. Factors of conversion assessed
for most of the land use land cover classes (agglomerations and saxocolon savannah not include), are
higher than 60 %. Simulations made on the basis of probabilities for an unit i to be converted to another
unit j reveals that the probability for forested area to be transformed into crops and fallows in the region
of Dassa and its environment, is high and varies from 30 to 53 %. Projections made for 2010 and 2020
horizon, reveals that in the future, while agglomerations, crops and fallows will spread, the forested
areas will decrease strongly.
The importance attached to the agriculture in the economic system and the rural migrations observed in
the study area explain the extension of the cultivated spaces. In this optic, lands will be scarce and
people will concentrate themselves on humid land like inland valleys, considered once as marginal
areas. The way the pressure on these new area is going, their future is not well insured as shown by the
examples of Kpole, Kotobo and Kpatiko inland valleys. The pressure occurred on these inland valleys is
expressed by the strong values of the land utilization rate (89.4 %). An immediate consequénce ofthese
signs is the degradation of animal and vegetal resources and in the future, the rupture of the ecological
stability of the area