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Accueil du site → Doctorat → Allemagne → 2008 → Evaluation of agricultural land resources in Benin by regionalisation of the marginality index using satellite data

Rheinischen Friedrich-Wilhelms-Universität Bonn (2008)

Evaluation of agricultural land resources in Benin by regionalisation of the marginality index using satellite data

Röhrig, Julia

Titre : Evaluation of agricultural land resources in Benin by regionalisation of the marginality index using satellite data

Auteur : Röhrig, Julia

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität Bonn

Grade : Doktorgrades (Dr. rer. nat.) 2008

Résumé
In the present work, the marginality index for agricultural land use was utilized to evaluate current and future biophysical resources for agricultural land use of Benin (West Africa) at a 1 km spatial resolution. The marginality index is an innovative capability evaluation approach that incorporates the main environmental factors, which limit agricultural production under low capital input. Furthermore, this index enables the detection of marginal sites, that is, sites prone to land degradation. In using this index, the feasibility of a global approach on a national scale was examined. Therefore, the same constraints, derived from input data at a higher spatial resolution, and adapted fuzzy logic based algorithms were used to determine the index for Benin. For the regionalisation, remote sensing data such as MODIS or SRTM were successfully applied to determine biophysical constraints. The outcome indicates that natural conditions are generally moderate suitable for agricultural land use in Benin, whereby most favoured regions are located in the south and centre of the country. Marginal sites can be found all over the country but in particular in northern regions. Currently, poor soils, limited length of growing period, and high rainfall variability are the crucial biophysical constraints on the national scale. Scenario analyses based on IPCC SRES scenarios A1B and B1 suggest that climate change will aggravate the natural suitability across Benin by 2025. Particularly temperature and the length of growing season will most likely impede future agricultural land use. In the context of this thesis, direct and indirect validation methods were conducted by applying GIS analyses and statistical tests. The direct methods are based on empirical knowledge and ground truth data recorded during field campaigns. For the indirect methods auxiliary data, namely disaggregated data of population density and trends of land degradation derived from NDVI data, were used. Both the direct and the indirect validation approach indicate the accuracy of the regionalisation outcome. Thus, the constraints considered herein on a global scale describing and defining marginal sites are, in an initial examination useful indicators on a national scale. Finally, based on biophysical constraints, population density, and trends of land degradation fields of investigations and corresponding location for national decision makers aiming a sustainable use of land resources were defined.

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