Observed trends in multiple breadbasket yield shocks

Abstract

Extreme climate events in breadbasket regions have become more frequent due to climate change, exposing crops to a greater frequency and intensity of abiotic stress. But by using observed crop yield statistics and an ensemble of statistical models, we demonstrate that over the last six decades the frequency of crop yield shocks in breadbasket regions has been decreasing due to both climate and non-climate factors. Here non-climate factors refer to interannual variability unrelated to abiotic stress, such as biotic stress and management decisions. We find that although the risk posed by extreme heat to crop yields has been increasing, this risk has been offset by changes to precipitation, extremely cold days, and average growing season temperature in many breadbaskets. As a result, total climate-related crop yield shocks have been decreasing for soybeans and wheat, while they have remained roughly constant for maize. Meanwhile, non-climate risks to crop yields have decreased in nearly every breadbasket region across crops. Because non-climate risks have decreased faster than climate risks, we find that the climate accounts for a greater proportion of crop yield shocks in the recent period (1991–2020) compared to an earlier period (1961–90). Our results indicate that extreme climate events are more important than ever to the relative stability of the food production system, even as the overall frequency of multiple breadbasket yield shocks decreases.