FAO.org

New trials are examining the impacts of climate change on indigenous tree species planted by small-scale farmers in Africa. Under the Sahelian Fruit Tree project (SAFRUIT ), for example, experiments are being conducted in the semi-arid West African Sahel, a region that has become drier in recent decades, on drought stress in trees, such as Adansonia digitata (baobab) and Parkia biglobosa (African locust bean), that are important to smallholder producers (Ræbild, A. et al., 2011). 

In nursery experiments, tree populations collected at various locations with differing rainfalls have been exposed to a range of watering regimes. Factors being measured include photosynthesis, water-use efficiency, water potential and chlorophyll fluorescence. The information obtained on the effects of different treatments on root development, seedling vigour and other important adaptive characteristics will inform subsequent germplasm distribution strategies. 

In some cases, the effects of climate change on seed distribution are already being taken into account in the region. Weber et al. (2008), for example, after conducting field trials measuring the growth, survival and wood density of Prosopis africana (a species used for wood production) in relation to rainfall patterns across seed collection sites, have recommended that germplasm transfers of the species should only be undertaken in a single direction, from drier to (currently) wetter zones. A similar strategy was adopted for a recent International Fund for Agricultural Development agroforestry project in the same region. Global circulation models used to explain environmental changes in temperature and precipitation profiles vary in their predictions of future rainfall in the Sahel. Some (e.g. Held et al., 2005) indicate conditions will be drier; others (e.g. Shanahan et al., 2009) project wetter conditions. Given the uncertainties of projections in the region, the most risk-averse option would appear to be one that put an emphasis on matching seed sources with the more limiting scenario of a drier future climate.