Smallholder farming and water scarcity: contributions, benefits, and limitations

Smallholders make up the vast majority of farms globally in terms of numbers (over 400 million), cultivate around 20% of global cropland, and produce 30% of global food. Although 70-80% of smallholders are located in areas already facing water scarcity which may be further exacerbated by climate change and population and economic growth, little is known about the relationship between smallholder farming and water scarcity. This study aims to shed light on this relationship, both regarding how water scarcity affects smallholders’ production and vice versa, how smallholders’ production and water productivity contribute to local water scarcity.

Hereto, we first estimated smallholders’ green and blue water consumption using ACEA 2.0 (AquaCrop-Earth@lternatives 2.0) in 56 countries around 2010, for main crops, and three farming systems. ACEA 2.0  is an updated version of the ACEA global gridded crop model based on AquaCrop-OSPy with a soil fertility module. It leverages a recently developed gridded global crop map that is both farm-size-specific and crop-specific. This inclusion allows us to incorporate the effects of soil fertility stress at an unprecedented level of granularity based on GAEZv4, which is highly relevant for evaluating the low-input rainfed, high-input rainfed, and (high-input) irrigated farming systems separately. The water productivity of smallholders was assessed in terms of a unit of water footprints and nutritional water productivity. Water scarcity was evaluated at the subnational basin level using global hydrological models PCR-GLOBWB, H08, and WaterGAP2-2C through ISIMIP 2a. The individual and combined effects of water and soil fertility stress on smallholders’ production were assessed and compared.