Exposure to a high degree of climate risk is a characteristic feature of rainfed agriculture in the drylands of sub-Saharan Africa and parts of South Asia. A growing body of evidence links unmitigated hydroclimatic variability to poor economic growth in developing countries. At a more local level, climate exerts a profound influence on the lives of poor rural populations who depend on agriculture for livelihood and sustenance, who are unprotected against climate-related diseases, who lack secure access to water and food, and who are vulnerable to hydrometeorological hazard. Several mechanisms by which climate risk impacts rural households combine with other factors to trap rural populations in chronic poverty. Climate change is expected to intensify many of the challenges facing dryland agriculture in Africa and South Asia, but in ways that can only be partially anticipated.
Improved control of water resources is a fundamental method for mitigating the impacts of climate variability. Methods range from small scale on-farm and community based measures with local control to large scale infrastructure with institutionalized and governmental control. There are tradeoffs inherent in any selection of water management approaches at any scale. One commonly overlooked tradeoff is the relationship between scale and reliability, where reliability of water supply decreases as the scale of water management intervention decreases. African countries and parts of India lack public or private infrastructure to provide storage to mitigate the variability of rainfall. The investments in agricultural water management that are viable for dryland agriculture in Africa in the foreseeable future provide only
partial control and leave substantial residual risk. The infeasibility of achieving a high level of water control across the vast dryland farming regions of Africa in the near to medium term, and increasing stress on groundwater and surface water resources in much of India point to the need to exploit every opportunity to deal with the residual climate risk that water control systems alone cannot mitigate.
We introduce the concept of residual risk to communicate the limitations of agricultural water management (or any singular approach) for managing climate risk and to facilitate the consideration of unmanaged climate risk. Managing that residual risk in dryland agriculture calls for several investments in parallel with improving agricultural water management. Opportunities include crop germplasm improvement, livelihood diversification, rural climate information systems, financial risk transfer and
improved hazard early warning and response.
We propose three specific areas of investment that we consider timely and promising. Each targets a different layer of risk: (a) climate-informed investment in water management to increase the resilience of agricultural development and stimulate investment; (b) rural climate information services to support adaptive management of water and production activities, as a way to manage residual risk with incomplete water control; and (c) integrated, multi-hazard (drought-flood-food insecurity) early warning systems to support more timely and better coordinated response to climatic shocks that exceed the coping capacity of rural communities.