Contribution of Agriculture to Deforestation in the Tropics: A Theoretical Investigation

This paper compares the deforestation path taken by profit maximizing agricultural firms in tropical regions to the path that will maximize social welfare based on optimal control techniques. We set up a theoretical problem where the socially optimal deforestation path that maximizes the discounted sum of net benefit of forest land use to society diverges from that of a farmer. We arrived at this conclusion after solving for the optimal choice of deforestation for both the private farmer and a social planner. The key source of this divergence in deforestation path is that the cost of deforestation is external to the farmer. The paper concluded that the farmer’s deforestation path leads to socially suboptimal outcome. Fiscal policy measures and public ownerships are recommended to deal with externalities that are inherent in forest land use. Keywords: Agriculture, Deforestation, Optimal contro

Evolution of traditional agroforestry landscapes and development of invasive species: lessons from the Pyrenees (France)

International audienceThe term agroforestry covers practices that are promoted to maintain or even enhance biodiversity. However, the relationship between agroforestry and invasive species is rarely addressed, even though the spread of such species is an important issue, not only ecologically but also economically and socially. Over the past few decades, humans have greatly accelerated the process of biological invasions, to such an extent that they are now recognized as the second cause of rapid decline in biodiversity. In France (as in other parts in Europe) abandonment of agricultural land in remote areas is a major problem having socio-economic, landscape and environmental implications. The objective of the research presented here was to find a method for studying the relationship between traditional agroforestry systems and invasive species, despite a lack of available data. We investigated the evolution of a traditional agroforestry system in the Pyrenean foothills, where invasive species are abundant, by implementing two complementary methods: i/ interviews highlighting the local stakeholders’ perception of landscape evolution, invasive species and the challenges they represent for the local traditional agroforestry landscapes, and ii/ detailed mapping of an area occupied by invasive plants, by means of very high resolution spatial technologies using UAV’s and aerial photography. The results show that invasive species have spread in relation with the abandonment of agricultural land, which has also led to “landscape closure” by the encroachment of natural afforestation. They also underline the difficulty of assessing the spread of invasive species. This situation is of major importance in terms of land-use planning, as the various stakeholders have different perceptions of the problem, and it raises questions about the sustainability of practices and territories