Climatic impacts on winter wheat yields in Picardy, France and Rostov, Russia: 1973–2010

The influence of climate on winter wheat yields were examined in two important global breadbaskets—the Picardy Region of northern France and the Rostov Oblast of southern Russia. Thirty-year climatologies were established for each region and the magnitude of change between 1973 and 2010 was quantified for a variety of climate variables important to crop development. Using a “first differences” analysis, the aspects of climate that winter wheat yields have been most sensitive to were identified and the impact of changes in these variables on winter wheat yield trends was quantified. A number of aspects of climate have changed at unprecedented rates in the two regions. Between 1973 and 2010, summer precipitation totals decreased by 61% and maximum summer temperatures increased by 4 °C in Rostov, while fall precipitation totals decreased by 9% and maximum spring temperatures increased by 2.4 °C in Picardy. In addition, winter wheat yields were strongly correlated with a number of climate variables, although the most important drivers of yield variability differed between the two regions. May and June average temperatures explained 49% (p < 0.0001) and 16% (p < 0.05) of interannual yield variability in Rostov, while in Picardy, November precipitation and minimum summer temperatures explained 26% (p ≤ 0.001) and 23% (p < 0.01). The climate variables that exhibited significant historical trends were often not the climate drivers that winter wheat yields were strongly correlated with in Rostov. Therefore, it appears that recent climate change has not significantly impacted winter wheat yield trends thus far in the region. However, in Picardy, there was partial overlap in the climate variables that winter wheat yields were most responsive to and those that have already exhibited significant changes over time. Consequently, climate change has likely caused an 11% decrease in winter wheat yield trends in the region.