Wheat models show climate change pressuring yields

A combination of multiple computer models of weather’s impact on wheat warns of a six per cent dent in world wheat production for every degree Celsius in temperature increase.

Scientists have been trying for 20 years to estimate effects of temperature increase and climate change on wheat production, which accounts for 20 per cent of calories consumed globally, but so far, according to a University of Florida release, different research groups have come up with different results.

A new international study, led by Florida agricultural and biological engineering professor Senthold Asseng, instead tests 30 different wheat crop models from the Agricultural Model Intercomparison and Improvement Project (AgMIP) against field experiments.

In the field experiments, the university said, growing season mean temperatures ranged from 15 C to 32 C, including experiments with artificial heating.

Wheat was chosen for the new study as “one of the world’s most important food crops,” Asseng said in the Florida release on Tuesday.

AgMIP is a separate international research project, spearheaded by the University of Florida and others, aimed at improving crop and economic models and the “next generation” of climate impact projections. The new study found many of the models “simulated yields well.”

However, the models used to predict wheat grain yield are “highly uncertain” when simulating how crops respond to temperature, the study said, and several of the AgMIP models were “less accurate at higher temperatures.”

The new study — published Dec. 22 as a letter in the journal Nature Climate Change — instead looked at results from the “ensemble median” of the 30 AgMIP models.

The study found the pooled modeling results “consistently more accurate in simulating the crop temperature response than any single model, regardless of the input information used.”

By extrapolating the model ensemble temperature response, the study authors said, the results indicate warming “is already slowing yield gains at a majority of wheat-growing locations.”

Those reduced gains appeared in the pooled modeling “despite observed yield increases in the past,” Asseng said in a university release.

Looking further out, global wheat production is estimated to fall by six per cent for each degrees Celsius of further temperature increase, the study said, and will become “more variable over space and time.”

Global temperatures have risen by more than 0.6 C and are projected to increase by 2 to 4 C by the end of the century, the university said, citing the International Panel on Climate Change.

New heat-tolerant wheat cultivars and crop management will be needed to counteract such a projected yield decline, Asseng said.

For that, he added, crop models will play a major role in developing new research strategies.

The study was co-authored by Frank Ewert, a professor with the Institute of Crop Science and Resource Conservation at the University of Bonn in Germany, and Pierre Martre, a senior scientist at the French national research institute INRA. –– AGCanada.com Network