Overriding the benefits
The World Resources Institute blog has a fascinating article about the greening of Ethiopia in recent years. This is largely based on a paper in Science of the Total Environment by Nyssen et al.
Jan Nyssen, a geographer at the University of Ghent, together with a large team of colleagues reviewed historic photographs of the Ethiopian highlands comparing them to more recent pictures of the same locations. They then assessed the change in greenery in the landscape, using a benchmarking methodology to assign a value, before performing a multiple regression analysis against possible causes.
The upshot of their paper is that these welcome changes seem to be largely the result of human activity - the landscape has greened the most in areas of higher population density. This seems to be related to factors such as the planting of eucalyptus trees in response to market demand for poles as well as more obvious conservation measures such as the use of terracing to prevent water run-off and soil erosion.