Climate Change Already Reducing Crop Yields: Study

Scientists warn that climate change resulting from global warming could reduce the world’s ability to grow food just when an increasing population needs it most.

Now, new research indicates it may already be happening.

A recent paper published in Sciencemagazine says two of the world’s four major crops show declining yields over the last 30 years and suggests changes in weather patterns may be to blame.

The paper, which appeared May 5 in the magazine’s online version, says global corn and wheat production declined by 3.8 and 5.5 per cent respectively between 1980 and 2008. Soybeans and rice were roughly equal in yield advances and declines.

The four crops make up roughly 75 per cent of the food calories people consume.

The paper, whose lead author is Stanford University researcher David Lobell, notes global average temperatures have risen by about 0.13 C per decade since 1980. An even faster warming pace of 0.2 C per decade is expected over the next 20 to 30 years.

The majority of countries in the world have experienced temperature increases for corn and wheat cropland at or above those levels. That trend is slowing harvest growth rates in most countries except, notably, the United States, according to the paper.

It does not mention Canada, although, by extrapolation, this country could be in the same category as the U.S.

The rate of temperature change is so significant that even good farming practices are not enough to compensate for the effects, according to the paper.

“Climate trends were large enough in some countries to offset a significant portion of the increases in average yields that arose from technology, CO2 fertilization and other factors,” it says.

The fact that “climate changes are already exerting a considerable drag on yield growth” makes the impact on global food prices even more real, the paper adds. It estimates that 6.4 per cent of global commodity price increases are due to climate change, even taking fertilizer use into consideration.

This scenario emphasizes the need for more research into breeding crops able to withstand changing weather patterns, said Stuart McMillan, weather and crops analyst with the Canadian Wheat Board.

But even that may not do the trick, he added.

“Even if we say we need to invest more in agriculture, it still may not be enough to offset some of the negative impacts of highly variable weather,” said McMillan.

“To me, it is very worrisome.” Some researchers suggest

Western Canada could be an overall winner from a warmer climate because its crop belt would extend farther northward.

But there’s no guarantee of that, McMillan said.

“It does not necessarily mean that suddenly we’ll have massive production north of Prince Albert or north of Swan River,” he said.

“We have limited infrastructure as you get farther and farther north. The soil gets poorer.”

Paul Bullock, a University of Manitoba soil scientist specializing in climate change, called theSciencepaper “interesting, but not necessarily predictive.”

The paper is not a forecast but only a statistical analysis, something the authors themselves acknowledge, Bullock said.

“If I was deciding on future food or agriculture policy in the USA, I would not base my decisions solely on these results.” [email protected]

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