BayCEER Workshop 2024

Climatic compound events and their effect on yield variability

Food scarcity under a growing world population is a pressing problem, especially amplified by increased yield variability due to climate change. Spatiotemporal variability on a small sub-country scale is rarely addressed in the literature so far, as well as the influences of climatic compound events (multiple extreme events occurring together) which are therefore the subject matter of this study.

To identify spatial differences in variability and stagnation, the time series of grain maize and winter wheat in the 96 counties of Bavaria since 1983 were decomposed into their trend and variability. The effect of extreme heat and drought on this variability was quantified in linear regressions. The magnitude of the effect was quantified by the reached explanatory values and was compared between the two crops, their development phases, and extreme events occurring independently from each other or together as compound events.

The variability of grain maize yields is mostly affected by the number of compound events during the whole development phase, with an average explanatory value of 0.40. The variability of winter wheat can be explained best by extreme events occurring independently from each other in the whole or the reproductive development phase (explanatory value of 0.31). Spatially, compound events have the strongest impact on the variability of maize yields in the central and northwestern areas of Bavaria. Those areas also have the highest share of maize in the agricultural land, and the large, homogeneous croplands with few buffers against climatic conditions might be an explanation for the strong influence of compound events.

With the results of this study, agricultural practices could be shifted from focusing on high yields to focusing on yield stability, as found in the south of Bavaria. Especially, as the frequency of compound events is supposed to increase with climate change.