Detecting the Influence of Protection on Landscape Transformation in Southwestern Ghana

Clement Aga Alo and R Gil Pontius Jr
Department of International Development, Community and Environment
Graduate School of Geography
Clark University
950 Main Street, Worcester MA 01610-1477, USA
Ph. +1 508 798 0731; Fax +1 508 793 8820

This paper examines the transitions among six land cover categories in southwestern Ghana and compares the transitions within  protected areas to those outside protected areas. Landsat Thematic Mapper (TM) satellite images of 1990  and  2000 are  used to create two land cover classifications, and then the two maps are compared to produce cross-tabulation matrices for both the protected and unprotected areas. These  matrices are analyzed according to their various components to identify the most systematic landscape transitions. It is necessary to consider the amount of gain in each category separately from the amount of loss of each category between 1990 and 2000. The amount of gain of a category is measured relative to the distribution of the other categories in 1990 in order to compute the amount of gain that would be expected in each category due to a random process of gain. The expected gain is then compared to the observed gain to detect systematic transitions. In a manner analogous to the analysis of gains, the amount of loss of a category is measured relative to the distribution of the other categories in 2000, and then the observed loss is compared to the expected loss due to a random process of loss. A non- random gain and a non-random loss in a particular transition imply a systematic process of change. The results show that, in the protected areas, Closed Forest transitions systematically to Bare Ground but outside the protected areas Closed Forest transitions systematically to Bush & Scattered Trees. Evidently, the process of land transformation in the protected areas is different from outside the protected areas. The research highlights the need for the practical application of this methodological approach to landscape change identification in Ghana. Identifying the strong signals of forest transformation is particularly important in the light of efforts by policy makers to halt or at least to slow deforestation in Ghana.

Keywords: deforestation, Ghana, matrix, land, protection

In: McRoberts, R. et al. (eds).  Proceedings of the joint meeting of The 6th International Symposium On Spatial Accuracy Assessment In Natural Resources and Environmental Sciences and The 15th Annual Conference of The International Environmetrics Society, June 28 – July 1 2004, Portland, Maine, USA.

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