Carbon sequestration potential of agroforestry systems in the West African Sahel: An assessment of biological and socioeconomic feasibility
In recent years, carbon (C) sequestration potential of agroforestry systems has attracted attention, especially following Kyoto Protocol's recognition of agroforestry as an option for mitigating green house gasses. Although the possible benefits of agroforestry in carbon (C) sequestration have been conceptually discussed, field measurements to validate these concepts have not been undertaken to any significant extent. In addition to the traditional agroforestry systems, improved practices and technologies are now being expanded into the dry regions such as the West African Sahel for perceived benefits such as arresting desertification, reducing water and wind erosion hazards, and improving biodiversity. Thus, it is imperative to investigate C sequestration potential of agroforestry practices in these regions. My research hypothesizes that the tree-based systems will retain more C in the systems both above- and below-ground than tree-less land-use systems. By joining the C credit market, the landowners could sell the C sequestered in their agroforestry systems.
My research consisted of three components. The first examined C (biomass + soil) stored in five target land-use systems: two traditional parkland systems involving Faidherbia albida and Vitellaria paradoxa trees as the dominant species, two improved agroforestry systems (live fence and fodder bank), and land that is out of cultivation (abandoned or degraded) in the Ségou Region, Mali. The second component involved a study of soil C dynamics of these systems: the extent of soil C storage/accumulation by trees and stability of the C accumulated were investigated. In the third component, socioeconomic feasibility of the agroforestry systems was examined in the context of C sequestration and C credit sale.
Research results show that the selected agroforestry systems have the potential for sequestering more C both above- and below-ground than in tree-less land-use systems, and that the trees tend to contribute to storing more stable C in the soil. Among the selected land-use systems, live fence and fodder bank are more suitable to start as agroforestry C sequestration projects than the traditional parkland systems for smallholder farmers in the studied region. Between the two improved systems, live fence has higher C sequestering potential per unit area and is economically less risky than fodder banks. Adopting these systems on cultivated land rather than on abandoned land is likely to sequester more C and be more profitable. Since parklands are traditionally practiced, they are not likely to qualify as a new C sequestration project soon. Nevertheless, F. albida trees are more attractive than V. paradoxa trees in terms of C sequestration potential.
These results can be used for development of recommendations and guidelines on selection of land use-systems and species and their management, for planning successful C sequestration projects in the West African Sahel.
