Predicting the current and future suitable habitats of cassava and cassava brown streak disease in Africa

Abstract

Cassava (Manihot esculenta) is among the most important staple crops globally. In sub-Saharan Africa, it is cultivated mainly by subsistence farmers who depend directly on it for their socio-economic welfare. However, its yield in some regions has been threatened by several diseases, especially the Cassava brown streak disease (CBSD). Changes in climatic conditions enhance the risk of the disease spreading to other planting regions. This work aimed to identify, characterize and map the current and potential future suitable habitats for cassava and cassava brown streak disease in Africa. We obtained occurrence data for cassava in Africa from the Global Biodiversity Information Facility (GBIF), and cassava brown streak disease occurrences from published literature. We used an ensemble of four species distribution models (SDMs), together with environmental covariates to characterize the current and future distribution of cassava and CBSD in Africa. Our results identified isothermality (Bio03, relative importance: 31.6%) as the highest contributor to the current distribution of cassava, while cassava cassava-harvested area (CHA, 14.6%) contributed the most to the current distribution of CBSD outbreaks. The geographic distributions of these target species are also expected to shift under climate projection scenarios. Using the recent climate scenarios from the Coupled Model Intercomparison Project (CMIP6) for the mid-term (2041-2060) and long-term (2061-2080) in Africa, our study highlights suitable habitats for cassava, as well as one of its economically important diseases (CBSD). For cassava, about 54.6% (16.2 million km²) of the continent is currently suitable for cassava production. These suitable habitats (i.e., suitability above 0.2) were predicted to be located predominantly in Sub-Saharan Africa. On the other hand, approximately 33.7% of Africa's land area (10.2 million km²) is currently at risk of CBSD spread. Based on our findings we propose that improved cassava varieties tolerant to CBSD should be deployed in all cassava production regions