Climate change may greatly affect the production of corn and wheat by 2030 if current trends continue, according to a new study. Corn yields are projected to decline 24 percent, while wheat could potentially see growth of about 17 percent. Along with rice and soybeans, these crops provide nearly two thirds of human food consumption, so the changes could have global effects. The results were published in the journal Nature Food.
Using advanced climate and agricultural models, scientists found that the change in yields is due to projected increases in temperature, shifts in rainfall patterns, and elevated atmospheric carbon dioxide concentrations from human-caused greenhouse gas emissions. These changes would make it more difficult to grow corn in the tropics, but could expand wheat’s growing range.
“We did not expect to see such a fundamental shift, as compared to crop yield projections from the previous generation of climate and crop models conducted in 2014,” said lead author Jonas Jägermeyr, a crop modeler and climate scientist at NASA’s Goddard Institute for Space Studies and Columbia University’s Earth Institute. The projected corn response was surprisingly large and negative, he said. “A 20 percent decrease from current production levels could have severe implications worldwide,” he said.
To arrive at their projections, the research team used two sets of models. First, they used climate model simulations from the international Climate Model Intercomparison Project-Phase 6 (CMIP6). Each of the five CMIP6 climate models used for this study runs its own unique response of the earth’s atmosphere to greenhouse gas emission scenarios through 2100. These responses differ somewhat due to variations in their representations of the planetary climate system.
Then the research team used the climate model simulations as inputs for 12 state-of-the-art global crop models that are part of the Agricultural Model Intercomparison and Improvement Project (AgMIP), an international partnership coordinated by Columbia University. The crop models simulate on a large scale how crops grow and respond to environmental conditions such as temperature, rainfall and atmospheric carbon dioxide, as provided by the climate models. Each crop’s behavior is based on its real life biological responses studied in indoor and outdoor lab experiments.
In the end, the team created about 240 global climate-crop model simulations for each crop. By using multiple climate and crop models in various combinations, the researchers became confident in their results.
“What we’re doing is driving crop simulations that are effectively growing virtual crops day by day, powered by a supercomputer, and then looking at the year-by-year and decade-by-decade change in each location of the world,” said Alex Ruane, a Goddard Institute scientist and coauthor of the study.
The study focused only on climate impacts; the models do not address economic incentives, changing farming practices, or adaptations such as breeding hardier crop varieties, although that is an area of active research. The research team plans to look at these angles in followup work, since they will also determine the fate of agricultural yields in the future as people respond to climate-driven changes.
Soybean and rice projections also showed regional change patterns, but at the global scale the different models still disagree on the overall impacts from climate change. For corn and wheat, the climate effect was much clearer, with most of the model results pointing in the same direction.
Corn, or maize, is grown all over the world, with large quantities produced in countries nearer the equator. North and Central America, West Africa, central Asia, Brazil and China will potentially see their maize yields decline in the coming years as average temperatures rise across these breadbasket regions, putting more stress on the plants.
Wheat, which grows best in temperate climates, may see a broader area where it can be grown as temperatures rise, including the northern United States and southern Canada, the north China plains, central Asia, southern Australia, and East Africa. However, these gains may level off by mid-century.
Temperature is not the only factor the models consider when simulating future crop yields. Higher levels of carbon dioxide in the atmosphere have a positive effect on photosynthesis and water retention. This increases crop yields, but often at a cost to the nutritional values of crops. This effect happens more so for wheat than maize. Rising global temperatures also are linked with changes in rainfall patterns, and the frequency and duration of heat waves and droughts, which can affect crop health and productivity. Higher temperatures also affect the length of growing seasons, and accelerate crop maturity.
“You can think of plants as collecting sunlight over the course of the growing season,” said Ruane. “They’re collecting that energy and then putting it into the plant and the grain. So, if you rush through your growth stages, by the end of the season, you just haven’t collected as much energy.” As a result, the plant produces less total grain than it would with a longer development period. “By growing faster, your yield actually goes down.”
“Even under optimistic climate change scenarios, where societies enact ambitious efforts to limit global temperature rise, global agriculture is facing a new climate reality,” Jägermeyr said. “And with the interconnectedness of the global food system, impacts in even one region’s breadbasket will be felt worldwide.”
Adapted from a press release by NASA.