The Sahel region is becoming greener, but in unexpected ways

The Sahel region is becoming greener, but in unexpected ways

The Sahel region south of the Sahara desert is well known for the disastrous droughts that struck the region in the 1970s and 1980s, which ignited global concerns about a remorselessly advancing desert perpetuated by unsustainable farming practices. New climate data shows, however, that the decline in rainfall during the 1970s and 1980s was, in a global historical perspective, an exceptionally rapid and enduring climatic event. The recovery in rainfall since the crisis period is thus expected to be accompanied by a regreening (returning vegetation) of Sahelian landscapes. Such a regreening is also documented for the region. However, as a recently published study by Hendrik Hänke and co-authors based on a case study from northern Burkina Faso shows, it is not the same trees and bushes that returns in the landscape. Instead, a new mix of more drought tolerant species dominates and many previously common trees are in decline. This is an important, surprising and somehow paradoxical finding, as more rain is not expected to stimulate a shift to trees and bushes that are adapted to a drier climate. Hence, the results works against the logic that more rain will allow more moisture demanding vegetation to grow. How is this possible? The answer is that not only the amount of rainfall, but also human land use practices, has a decisive effect on what trees and bushes thrive in a specific environment. This conclusion challenges the dominant scientific understanding of the Sahelian regreening as almost exclusively driven by returning rainfall, and points at the importance of a better understanding of how changing social-ecological relations may replace traditional agroforestry landscapes with new a new mix of trees and bushes. Such a nuanced understanding provide an important basis for any organization that wishes to design suitable policies for climate change adaptation, biodiversity conservation and the sustainable delivery of ecosystem services that benefit local livelihoods in one of the world’s poorest regions.

Graphical abstract

 

A conceptual model illustrating different tree cover pathways in relation to species composition and rainfall variability. The diagram could be interpreted along any, even small, shifts along these gradients. Wet and dry habitat indicates species thriving under relative wetter to dryer conditions. Brown and green refers to a sparse and dense woody vegetation cover, respectively.

The article is available here: https://doi.org/10.1016/j.landusepol.2016.08.023