Global warming is likely already taking a toll on world wheat and corn production, according to a new study led by Stanford University researchers. But the United States, Canada and northern Mexico have largely escaped the trend.
|A combine harvester reaps, threshes and winnows its way through a field of corn at harvest time. Yields in the U.S., Canada and northern Mexico have yet to feel the impact of global warming. (Photo by Bruce Fitz / U.S. Department of Agriculture)|
"It appears as if farmers in North America got a pass on the first round of global warming," said David Lobell, an assistant professor of environmental Earth system science at Stanford University. "That was surprising, given how fast we see weather has been changing in agricultural areas around the world as a whole."
Lobell and his colleagues examined temperature and precipitation records since 1980 for major crop-growing countries in the places and times of year when crops are grown. They then used crop models to estimate what worldwide crop yields would have been had temperature and precipitation had typical fluctuations around 1980 levels.
The researchers found that global wheat production was 5.5 per cent lower than it would have been had the climate remained stable, and global corn production was lower by almost 4 per cent. Global rice and soybean production were not significantly affected.
The United States, which is the world's largest producer of soybeans and corn, accounting for roughly 40 per cent of global production, experienced a very slight cooling trend and no significant production impacts.
Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn (or maize) yields related to the rise in global temperature. "Yields in most countries are still going up, but not as fast as we estimate they would be without climate trends," Lobell said.