Warmer mean and extreme temperatures, growing atmospheric CO2 concentrations, altered precipitation regimes, and drought patterns affect agricultural production worldwide. Crop yields are expected to decrease under future climate conditions, with the largest adverse impacts expected at low latitudes. In parallel, the world is experiencing rising demand for crop production, which stems from increasing affluence and consumption habits, changing living standards and biofuel proliferation. Meeting such demand is a formidable and multi-faceted challenge, even more relevant considering the COVID-19 pandemic and the war in Ukraine impacts on food-security worldwide.

Insufficient food supply still lies among the multiple causes of food insecurity in African countries. This is often provoked by adverse climatic conditions, which can be further aggravated by climate change. In this work, we observe changing patterns of precipitation, evapotranspiration and soil moisture, which can undermine local conditions for agriculture. Furthermore, recent evidence suggests that crop yields will decrease under future climate conditions; in low-latitude regions especially, where even moderate temperature increases will negatively impact crop yields due to the current proximity to crop-limiting temperature thresholds for suitable production. We describe heterogeneous impacts of climate change across African croplands. A marked drying process due to irregular and increasingly sporadic rainfall in the North of Africa causes a decrease in the water footprint of crops. With less water available in the soil, it will be necessary to compensate with irrigation to maintain agricultural production. In the Gulf of Guinea, on the other hand, rising temperatures cause an increase in the water footprint of crops, since the evapotranspiration process intensifies and more water is required.

For this reason, researchers and policymakers have called for a boost in crop yields through the enhancement of agricultural production practices on the African continent. Recent studies have suggested multiple strategies for achieving this, including sustainable intensification, which shows a large potential for meeting demand challenges without further encroachment on natural ecosystems. However, it is not yet clear to what extent this might exacerbate the impacts on water resources and how climate change may limit its effectiveness.

The water footprint scenarios developed in this study have been used to assess (i) the implications of an agricultural intensification scenario for blue water and green water; (ii) the impact of climate change on green and blue water demand, through crop-specific evapotranspiration projections, which shed light on the impact of temperature trends and rainfall variability on soil moisture and additional irrigation requirements;  (iii) the potential of yield intensification to support the improvement of food security, within a water-food nexus framework. We assume crop productivity to increase up to the maximum attainable yield by 2040, as a result of an intensive and high-input agricultural management projected on the continent and of the expansion of irrigation infrastructure over all rainfed harvested areas. This assumption has been constrained with time-independent harvested areas, constant at the year 2010 extension, to simulate a pathway of agricultural intensification over the continent.

We show that higher yields can contribute to reducing the vulnerability of the African agricultural system but require extensive blue water supply. According to our estimates, the irrigation of the crops considered will require between 80 (by 2040) and 100 (by 2100) km3 of additional blue water under the worst-case climate scenario. But, positively, the observed potential yield increase is highest in those countries that today suffer most from malnutrition, such as Congo, Somalia or South Sudan, where more than 80% of the population is food insecure. Therefore, improved agricultural management could represent a reliable strategy to strengthen food security and for adapting to the negative impacts of climate change, if coupled with responsible and efficient water use.

Our intent is not to recommend the intensification of African agriculture, but to anticipate some of its consequences, especially those related to sustainable water resources management. We aim to give a critical perspective from the water footprint side to address the commonly adopted strategy of intensification. We are aware that agricultural intensification is a main driver of ‘planetary boundaries’ transgression and the pledge of yield increase comes at an environmental and social cost. High inputs of agro-chemicals leach into soils and water bodies and threaten species living on cropland and in surrounding habitats. By promoting maximized production and a shift toward monoculture, agricultural intensification may eliminate redundancy and diversity within agroecosystems, drive habitat homogenisation and make agriculture more vulnerable to droughts, pests and other shocks. In addition, the investments in modern technology might force a transition from smallholder farming to large-scale commercial agriculture, marginalizing rural communities, and harming livelihoods and local traditions.

Still, semiarid regions where crops are mainly cultivated under rainfed conditions, typically show the greatest yield increase when irrigation water is supplied. Therefore, the expansion of irrigation infrastructure, supported by sustainable water management represents a fundamental step towards the strengthening of food security across the continent, in the context of a changing climate. Slowing the increase in agricultural water use is of primary importance and any strategy aimed at this should integrate food security, socio-economic and environmental well-being, not disregarding locally available technologies, knowledge and rural livelihoods.