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Ademola K. Braimoh and Paul L. G. Vlek

Abstract

Multitemporal Landsat Thematic Mapper (TM) images for 1984, 1992, and 1999 were used to map and detect land-cover changes in a 5400-km2 area within the Volta Lake basin of Ghana. The most dominant land-cover change was the conversion of natural vegetation to cropland, which occurred at an annual rate of 5%. While the data suggest an increase in human pressure, reversible change in woodland and grassland occurred in 4% and 2% of the landscape, respectively. A higher proportion of reversible land-cover changes relating to fallow agriculture occurred in about 14% of the landscape, whereas a higher overall increase in woody biomass (10%), compared to an overall decrease of 9%, indicates a certain level of rainfall-induced resilience in the ecosystem. Further research is needed to quantitatively evaluate the mechanisms enhancing vegetation recovery in dryland areas.

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Ademola K. Braimoh and Paul L. G. Vlek

Abstract

Relationships between cropland change and presumed determinants were analyzed at scales ranging from 30 to 5100 m using logistic regression. The plot of the odds ratio across the spatial scales indicated that both biophysical and social variables were important in explaining cropland change. In the first period (1984–92), biophysical factors were the dominant factors, while market-related variables were more dominant between 1992 and 1999. Response to changing economic opportunities was the underlying cause of this trend. Policies that would make commercialization of agriculture viable are required in the Volta basin of Ghana.

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Ademola K. Braimoh and Paul L. G. Vlek

Abstract

The objectives of this study were to quantify land-cover changes. A short-term projection of land-cover distribution in a 2400-ha (1 ha = 10 000 m2 ) area of northern Ghana was generated. Landsat Thematic Mapper images acquired in 1984, 1992, and 1999 were used for land-cover mapping, whereas land-cover projections were carried out using transition probability techniques. Remote sensing analyses showed that in the first period (1984–92), the dominant land-cover change process was the expansion of the built-up area (26 ha yr−1) as a result of an increase in demand for housing by the increasing population. Expansion of the built-up area continued at the rate of 35 ha yr−1 in the second period (1992–99), as well as development of peri-urban agriculture (24 ha yr−1) to meet the food demand of the rapidly growing population. Projection of land-cover distribution showed that the built-up area would further increase at the expense of cropland and natural vegetation, covering about 39% of the landscape by 2006. Policy implications of this trend are discussed.

This paper is part of a special theme issue on land use and ecosystems.

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