Mapping future crop yield trends across Europe by auto-adaptive regression modelling

A statistical crop yield model developed by the author, ABSOLUT (Conradt 2022, https://doi.org/10.1007/s00484-022-02356-5 ), is capable of identifying the time aggregates of meteorological variables or indices most relevant for agricultural yields. Using climate change scenarios as input to the model calibrated on recent weather and yield data future crop yields have been projected for the districts of Germany and for Europe's NUTS-2 regions.

Previous research has shown that while large parts of inter-annual crop yield variations can already be explained by aggregates of temperature, precipitation, and solar radiation only, model performances are regularly increased by also including drought indices representing water stress related to soil conditions (see also Eini et al. 2023, https://doi.org/10.1016/j.agwat.2022.108107 ). This holds especially for maize and root crops (e.g. potatoes, sugar beets) grown in mid-latitudes and harvested in autumn. Consequently, all crop yield scenarios presented here are obtained from predictors including Standardized Precipitation Evaporation Indices (SPEI, Vicente-Serrano et al. 2010, https://doi.org/10.1175/2009JCLI2909.1 ) on 3- or 12-month scales.

Results show strong weather effects on green maize (high coefficients of determination in leave-one-out validation) and a generally negative outlook for the future: The median scenario under CMIP6 SSP370 climate shows 5–15% declines in green maize yields for the years around 2050 compared to nowadays levels in most European regions. Southern France, Northern Italy, and Bulgaria are predicted to experience yield losses of even more than 20%, albeit with lower reliability. The Mediterranean countries however include also some regions with positive trends on low confidence levels. In a more distant future of the years around 2080 the spatial pattern remains unaltered, but the strength of the changes will have doubled.

For winter wheat the model performs better in the eastern parts of Europe. Only slight declines in yield of 0–10% are projected there for the 2050 time slice; for the years around 2080 losses of more than 25% have to be expected, though. Drastic losses of 20–50% and exceeding 50% in the more distant future threaten many Mediterranean regions. There is however also a stable outlook for Britain and Ireland, The Netherlands, Belgium, and the North-Western parts of France. Yield increases are projected for Southern Finland and the Baltic states. This regional exception to the general downward perspective is in good agreement with a map presented in the European Drought Risk Atlas (Rossi et al. 2023, https://doi.org/10.2760/608737 ).