Previous studies assessing agricultural impacts have demonstrated that the effects depend on the crop, cropping season and region within Europe, but few studies have considered the cropping system responses to changes in the frequency and severity of climatic extremes (see, for example, ref. for the Iberian Peninsula). However, it is well known that the impacts of such extreme events can be substantial. Previous studies have emphasized the possibility of considerable northward expansion of the thermal suitability of crop production in Europe (indirectly suggesting major shifts in the location of agriculture production) without fully considering changes in the risk of adverse events. Our results show that, despite large uncertainty in climate projections within the CMIP5 ensemble, the overall adverse event frequency is much more likely to increase than decrease, which is the case for all of the sites in the analysed European domain.
From the standpoint of production stability, it is encouraging that some central (WS and VI) and north-western European (WA, MA and TR) growing areas are likely to face comparatively small increases in adverse event occurrence. Nevertheless, the fact that the majority of the sites show a greatly increased probability of single adverse events suggests, in turn, that risk of crop failure would increase across large portions of the European wheat-cropping area. Such a development would have profound repercussions given the importance of European wheat production in the global food trade. Moreover, more frequent adverse conditions for wheat at any particular location would probably be accompanied by yield reductions in other crops (both cereals and non-cereals), as their growing seasons and sensitive periods at least partly overlap. We stressed that the results are valid for wheat that is grown on free-draining soils with the ability to hold a significant amount of water available to plants. The severity and frequency of some of the adverse events (for example, drought stress or water logging) could be different on sandy or heavy clay soils.
Our results highlight the potential of adverse impacts of a changing climate on wheat and show that the associated potential adaptations to these impacts should consider adverse and extreme weather event effects in a more comprehensive way than is usually done in impact assessments based on crop models, which very often do not include such event effects. Moreover, focusing on single adverse events may lead to an incomplete risk perception. Impact severity will depend on the cultivar characteristics and, obviously, on the spatial and temporal climate change patterns. This dependence calls for a regionalization of adaptation strategies: whereas for some regions it is important to breed cultivars that are capable of coping with an increased frequency and magnitude of heat stress around flowering, in some regions it will be equally important to maintain tolerance of low temperatures. In other regions, research should focus on water logging, lodging or field accessibility. Therefore, national and EU research and agricultural policies should encourage and promote response diversity of wheat varieties, which would enhance climate resilience by enabling the crop to cope with different region- and season-specific threats, rather than focusing on one or two particular issues.