Each degree of global warming will cut into harvests of the world’s staple crops, according to a new study that takes a broad view of the agricultural research field. Twenty-nine researchers published the paper this week in Proceedings of the National Academy of Sciences.
Wheat, corn, rice and soybeans make up two-thirds of humans’ caloric intake. Each crop reacts differently to rising temperatures, and the effects vary from place to place. On average, though, the world can expect 3.1 to 7.4 percent less yield per degree Celsius of warming, according to the research.
The Paris climate agreement, which the United States plans to quit, has committed the international community to less than 2 degrees Celsius of warming by the end of the century.
Rice, a main food source for developing countries, could decline an average of 3.2 percent. Some research pointed toward an even greater impact — as much as 6 percent. Soybeans, the world’s fourth-most important commodity crop, could yield 3.1 percent less per degree.
The researchers only studied the direct effect of rising average temperatures, but indirect effects could change things, too. Water stress and drier soils might drag down harvests. So could more frequent heat waves. Climate change could also affect pests, weeds and diseases.
The United Nations predicts the world’s population will grow to 9.8 billion by 2050 from 7.6 billion today. Warmer conditions could make it harder to grow enough food for so many mouths, and the crops that do grow could offer fewer nutrients.