The world’s most productive agricultural regions face the greatest losses from climate change, with major farming areas in wealthy nations potentially losing as much as 40% of their maize and wheat production this century, a comprehensive new study has found.

In their analysis of more than 12,000 regions across 55 countries, a team of researchers from top U.S. and international institutions found that for every 1°C increase in global temperature, global food production could decline by approximately 120 calories per person per day—equivalent to 4.4% of current daily consumption.

The study, published in Nature, reveals that even when so-called climate adaptation strategies are undertaken, “breadbasket” regions are particularly vulnerable, and will face substantial reductions in the production of most key food crops, presenting a concerning outlook for global food security.