The issue of economic costs and in particular macroeconomic costs of the degradation of land is slowly becoming a priority one in international meetings on the development of dry regions. It is also being combined with the cost of inaction revealed by the Organisation for Economic Co-operation and Development in 2005. However, there are not many practical studies of the cost of degradation of land on a national level and furthermore the few there are not referenced very well in scientific publications. This article will describe different studies undertaken mainly by the World Bank, their methods and limitations as well as their results. Two types of approach can be distinguished on the whole: (i) modelling principally based on understanding processes of rainfall erosion, based on plot surveys and (ii) furthermore more spatial approaches dividing the areas affected according to the main economic activities which take place there. The results show that the cost of desertification is often equal to or greater than the agricultural growth of the countries concerned which brings into question the reality or sustainability of their rural development.

Analyses of the rate of return on investments in the fight against desertification are still inadequate. Referring to several key studies on this issue and a review of several anti-desertification projects, the document shows that the rates of return of successful projects are often under-evaluated because they are generally limited to agricultural production gains. However the delays in return on investment observed for the rehabilitation of degraded land can also explain why anti-desertification projects are so poorly deployed among local populations who are not able to bear the cost. Finally we consider investment in the recovery and maintenance of land as a motor of rural development. Should one not as well in order to fight against desertification, promote small industries producing products from dry regions as well as ecotourism or service activities?