The costs of land degradation in sub-Saharan Africa

The overriding question that this article addresses is: What are the immediate and future costs of land degradation for a nation? The objectives of the analysis are to find appropriate measures to express the national level costs of land degradation, and suitable methods to estimate such measures. Furthermore, the aim is to document and interpret the results of existing studies. To meet these objectives, a set of 12 studies from Sub-Saharan Africa (SSA) is reviewed, using a consistent, cross-study analytical framework derived from the objectives above, With regard to measures of the cost of land degradation, this article identifies ten different dimensions, which illustrate the importance of qualifying statements about ''the costs of land degradation'' by rigorous clarification of what type of measure has been used. Furthermore, with regard to methods of deriving costs of land degradation, this article illustrates a spectrum of approaches. One sub-group has used a replacement cost approach, while a productivity loss approach has been used in the majority of the studies reviewed. The latter approach is further sub-divided into five different categories ranging from the most informal to the most rigorous. It is evident that very few original estimates exist of soil loss yield decline functions in Sub-Saharan Africa. Hence, some of the basic work in this area is ''recycled'' for use in areas that may exhibit quite different conditions. Finally, with regard to study results, there is considerable variance of cost estimates pertaining even to the same country. These differences can be explained, however, and a rational assessment allows a choice of the most appropriate results. Results across countries are reasonably well clustered in terms of their productivity impact per soil loss unit. With local knowledge of soil conditions, but in the absence of local yield loss data, this provides a useful interval of reasonable assumptions. As one would expect, the national costs of land degradation vary considerably across countries. This sometimes leaves room for considerable investment in soil and water conservation, but should not invoke images of a rapidly approaching doomsday.