Land suitability modeling of shea (Vitellaria paradoxa) distribution across sub-Saharan Africa

Shea trees (Vitellaria paradoxa, synonym: Butyrospermum paradoxum or parkii) have been botanically recorded in 21 countries across semi-arid sub-Saharan Africa. Dried kernels are the source of shea butter, a stearic/oleic rich edible oil or fat consumed locally, and internationally as an ingredient in the multi-billion dollar cosmetic and confectionary sectors. For millennia shea has been a staple edible oil crop, significantly contributing to nutritional health, livelihoods and the community well-being of women collectors and their families. This research is the first known attempt to predict the potential shea distribution and production using Geographic Information Systems (GIS) by combining binary and suitability layers developed from eight parameters: land-use, temperature, precipitation, elevation, fire, Normalized Difference Vegetation Index (NDVI), soil-type and soil-drainage. The model is verified and validated using 302 GPS coordinates of shea trees and distributions developed by USAID West Africa Trade Hub (WATH). The model gives an extensive shea tree suitability area of 3.41 million km2 across 23 countries with rural population of 112 million, including 18.4 million women collectors. Using conservative estimates, 1.84 billion trees (1.07 billion in high stearin areas) are predicted. Given current population densities, a collected crop of 2.44 million tons of kernels yielding greater than 800 thousand tons of shea butter is estimated (1.63 million tons high stearin kernel). As scientific knowledge on shea expands, the model's suitability criteria can be fine-tuned and climate change, development and urbanization impacts estimated. The suitability model developed is thus useful to governments, non-government organizations, researchers, and industry in planning projects and investments in rural development, climate change, food security and biodiversity through shea production.