A global and spatially explicit assessment of climate change impacts on crop production and consumptive water use

Abstract

Food security and water scarcity have become two major concerns for future human's sustainable development, particularly in the context of climate change. Here we present a comprehensive assessment of climate change impacts on the production and water use of major cereal crops on a global scale with a spatial resolution of 30 arc-minutes for the 2030s (short term) and the 2090s (long term), respectively. Our findings show that impact uncertainties are higher on larger spatial scales (e.g., global and continental) but lower on smaller spatial scales (e.g., national and grid cell). Such patterns allow decision makers and investors to take adaptive measures without being puzzled by a highly uncertain future at the global level. Short-term gains in crop production from climate change are projected for many regions, particularly in African countries, but the gains will mostly vanish and turn to losses in the long run. Irrigation dependence in crop production is projected to increase in general. However, several water poor regions will rely less heavily on irrigation, conducive to alleviating regional water scarcity. The heterogeneity of spatial patterns and the non-linearity of temporal changes of the impacts call for site-specific adaptive measures with perspectives of reducing short- and long-term risks of future food and water security.

Figure 1. The impacts of climate change on crop production.

(a) and (b) show the spatial distribution of confidence levels of increase or decrease for aggregated crop production index (API) in the 2030s and the 2090s, respectively, in comparison to the 1990s. (c) shows the relative change (%) of API caused by climate change on the global and continental scales.

Figure 2. The impacts of climate change on consumptive water use (CWU).

(a) and (b) show the spatial distribution of confidence levels of increase or decrease for aggregated CWU index (AWI) in the 2030s and the 2090s, respectively, in comparison to the 1990s. (c) shows the relative change (%) of AWI caused by climate change on the global and continental scales.

Figure 3. The impacts of climate change on irrigation water proportion.

(a) and (b) show the spatial distribution of confidence levels of increase or decrease for aggregated irrigation water proportion index (AIWI) in the 2030s and the 2090s, respectively, in comparison to the 1990s. (c) shows the relative change (%) of AIWI caused by climate change on the global and continental scales.

Figure 4. Change of irrigation water proportion in the 2030s in relation to water scarcity.

Water scarcity is defined for the regions where total water withdrawal exceeds 40% of the freshwater resources, while water stress is defined for the regions where total water withdrawal is 20%–40% of the freshwater resources. ABI indicates irrigation water proportion.

Figure 5. Change of irrigation water proportion in the 2090s in relation to water scarcity.

Water scarcity is defined for the regions where total water withdrawal exceeds 40% of the freshwater resources, while water stress is defined for the regions where total water withdrawal is 20%–40% of the freshwater resources. ABI indicates irrigation water proportion.

Figure 6. Latitudinal distribution of harvest area, and impacts of climate change on crop yield for wheat, maize and rice.

A cut-off for changes in yield >150% is used to allow for a better interpretation of the impacts of climate change in current major growing regions where changes are mostly within a range of −50% – +50%. Cut-offs often occur at the latitudes where harvested areas are marginal currently.

Figure 7. Latitudinal distribution of harvest area, and impacts of climate change on consumptive water use (CWU) for wheat, maize and rice.

A cut-off for changes in CWU >150% is used to allow for a better interpretation of the impacts of climate change in current major growing regions where changes are mostly within a range of −50% – +50%. Cut-offs often occur at the latitudes where harvested areas are marginal currently.

Figure 8. GCM and scenario uncertainties indicated by relative difference for crop production and CWU at global and continental levels in the 2030s and the 2090s.