Drought or high temperatures: which is the main threat to agricultural yields in Central Europe?

Recently, the European Commission's Joint Research Centre published the European Drought Risk Atlas (Rossi et al. 2023, https://doi.org/10.2760/608737 ). It illustrates the spatial drought risk distribution for several economical sectors. For agriculture, observed yield losses of five crops (wheat, barley, maize, potatoes, and rice) were connected to numerous drought indices ranging from meteorology to river runoff. Temperature was however deliberately excluded from the analyzed drought factors.

A statistical crop yield model developed by the author, ABSOLUT (Conradt 2022, https://doi.org/10.1007/s00484-022-02356-5 ), showed that large parts of inter-annual crop yield variations can be explained by three meteorological factors only: monthly values of temperature, precipitation, and solar radiation. The model works in spatially disaggregated regions, e.g. for the approximately 400 German districts or for Austria split into 25-km tiles. For each sub-region and crop, the most relevant time aggregates of the meteorological factors and their individual importance for the yield estimation are automatically determined. For instance, in Central Europe a positive influence of solar radiation is regularly observed for spring barley; for winter wheat, negative effects of high temperatures towards the end of the growing season are the rule. However, in the colder climate of Northern Europe (Estonia) higher temperatures are generally associated with higher yields.

In addition or even instead of meteorological variables, ABSOLUT can also be trained on drought indices. Including drought information in addition to meteorological data will probably improve the yield estimations (cf. Eini et al. 2023, https://doi.org/10.1016/j.agwat.2022.108107 ). Dropping either temperature or drought information from the input will show the importance of each factor causing yield losses. In this contribution, I will show the results of respective experiments with ABSOLUT for winter wheat and silage maize in Central Europe in an attempt to answer the question in the title.