From blue to green water and back again: Promoting tree, shrub and forest-based landscape resilience in the Sahel

Enjoying the potential climate benefits of restoration requires linking key forest-water and land-atmosphere interactions to the existential benefits provided on the ground. We apply what we call the "forest-water and land-atmosphere interaction lens" to current strategies for improving landscape resilience in the West African Sahel and the concept of the Great Green Wall (GGW). The severe and extensive drought of the 1970's-1990's led many to assess future climate and promote strategies to counter the gradual southward expansion of the Sahara. The idea for the GGW, a wall of trees intended to slow desert encroachment, grew out of this period of tremendous upheaval and human tragedy. Despite partial recovery in the local rainfall regime, we know far too little about whether the GGW strategy can even work. Further, it seems disingenuous to ignore the climatic envelope, which sets the boundaries within which forest-water and land-atmosphere interactions occur. Applying the "forest-water and land-atmosphere interaction lens" to landscape restoration as a tool for achieving improved resilience and human welfare in the Sahel provides meaningful input for re-thinking the GGW strategy. We upgrade current knowledge with the specific biophysical conditions likely to better support appropriate forest-water and land atmosphere interactions in the region and further fit such approaches within the context of the climatic envelope. The principal components of an improved strategy include a focus on large scale precipitation recycling all the way from the West African coast on into the Sahel, as well as improved tree, shrub and forest cover in the Sahel proper to promote infiltration, groundwater recharge, rainfall triggering potential and land surface cooling. Agroforestry can further broadly promote landscape resilience in the greater region. Strategies broadly focused on increasing rainfall recycling, water availability and the promotion of landscape resilience appear more likely to steer future efforts in useful directions.