On European scale 30 year of annual crop yield data are related to dry and wet spells, detected by the drought indices SPI and SPEI. Goal of the study was to see if the fluctuations in crop yield can be explained by droughts or wet periods.
Worldwide drought is one of the most devastating hazards and can impact important sectors humans rely on. One of these is agriculture. Some research has been done to find relations between drought and crop yields mostly on country or regional level. Investigation on these relations for widely cultivated crops on European scale was still missing. To fill this literature gap we used 35-year of observed annual crop yield data of five selected crops (i.e. barley, wheat, sugar beet, potato and maize) and de-trended the data by i) moving average and ii) linear regression to eliminate multiannual trends due to technological development. The crop yield data were related to the meteorological drought indices Standardized Precipitation Index (SPI) and Standardized Precipitation and Evaporation Index (SPEI) given for 1979-2009, both including accumulation periods of 1, 2, 3 and 6 months. For both the drought indices as the crop yield data, information was gathered at NUTS2 level and up scaled to the European level and the three biggest climate regions, i.e. Atlantic, Continental and Mediterranean. SPI and SPEI were highly correlated and had to be divided over separated linear statistical models. The models showed that for the SPI as well as for the SPEI the highest correlations were found for barley and wheat in the moving average de-trended data set. Impacts of dry spells on crop yield at European scale is visible, but regional differences within biogeographical climate regions exist.