Abstract:
Inland valleys (IVs) in Africa are important landscapes for rice cultivation and are targeted by national governments to attain self-sufficiency. Yet, there is limited information on the spatial distribution of IVs suitability at
the national scale. In the present study, we developed an ensemble model approach to characterize the IVs suitability for rainfed lowland rice using 4 machine learning algorithms based on environmental niche modeling
(ENM) with presence-only data and background sample, namely Boosted Regression Tree (BRT), Generalized
Linear Model (GLM), Maximum Entropy (MAXNT) and Random Forest (RF). We used a set of predictors that
were grouped under climatic variables, agricultural water productivity and soil water content, soil chemical
properties, soil physical properties, vegetation cover, and socio-economic variables. The Area Under the Curves
(AUC) evaluation metrics for both training and testing were respectively 0.999 and 0.873 for BRT, 0.866 and
0.816 for GLM, 0.948 and 0.861 for MAXENT and 0.911 and 0.878 for RF. Results showed that proximity of inland
valleys to roads and urban centers, elevation, soil water holding capacity, bulk density, vegetation index, gross
biomass water productivity, precipitation of the wettest quarter, isothermality, annual precipitation, and total
phosphorus among others were major predictors of IVs suitability for rainfed lowland rice. Suitable IVs areas
were estimated at 155,000–225,000 Ha in Togo and 351,000–406,000 Ha in Benin. We estimated that 53.8% of
the suitable IVs area is needed in Togo to attain self-sufficiency in rice while 60.1% of the suitable IVs area is
needed in Benin to attain self-sufficiency in rice. These results demonstrated the effectiveness of an ensemble environmental niche modeling approach that combines the strengths of several models.
