How tree cover affects groundwater resources across African tropical drylands

General

An estimated 80% of the global population lack secure water resources. Many also lack ready access to fuel wood and other tree derived benefits. However, the current scientific paradigm says that we must choose which problem to solve as increasing tree cover always reduces water availability. Consider the costs if this thinking is wrong. In Africa, 175 M ha of degraded lands are judged suitable for tree planting which could significantly enhance people’s livelihoods. Our previous research in the seasonally dry tropics indicates that an intermediate tree cover can often improve groundwater recharge. This need testing on a larger scale, but if confirmed will upend the prevailing view in hydrology and have profound implications for policies affecting millions of livelihoods and the environment.  Thus, the aim of this project is to provide evidence for better policies and management that will benefit poor people in drylands by evaluating the novel “optimum tree cover theory” for groundwater recharge across African drylands. The project involves four leading institutions; SLU, ICRAF, WU and NMBU. We will use the Land Degradation Surveillance Framework; a unique dataset that is available across Africa. It consists of multiple variables, including tree cover and key soil variables. We will do complementary strategic measurements of soil water flow and tree water use to model groundwater recharge as a function of tree cover under common conditions of the seasonally dry tropics.