A warming planet gathers no crops?

Global warming is changing our economy, health and communities! New research has found that the world now faces a substantially increased risk, over the next two decades, of a major slowdown in the growth of global crop yields as a result of climate change.

Two authors, one from Stanford University, in California, the United States (US), and another from the National Centre for Atmospheric Research (NCAR), a US federal organisation managed by the University Corporation for Atmospheric Research, say the odds of a major production slowdown of wheat and corn, even with a warming climate, aren’t very high …

“But the risk is about 20 times more significant than it would be without global warming, and it may require planning by organisations that are affected by international food availability and price,” notes NCAR in a release about the new study: Getting caught with our plants down: the risks of a global crop yield slowdown from climate trends in the next two decades.

Claudia Tebaldi, NCAR scientist and a co-author of the study (published online in the July 2014 issue of the journal Environmental Research Letter), adds: “Climate change has substantially increased the prospect that crop production will fail to keep up with rising demand in the next 20 years.”

NCAR states that global yields of corn and wheat crops have typically increased by about one to two percent per year in recent decades. The United Nations Food and Agriculture Organisation projects that global production of major crops will increase by 13 percent per decade through 2030 – “likely the fastest rate of increase during the coming century”, the federal organisation points out.

“However, global demand for crops is also expected to rise rapidly during the next two decades as a result of population growth, greater per-capita food consumption and increasing use of biofuels,” it adds.

David Lobell, a professor at Stanford and the other author of Getting caught with our plants down, points out that he wanted to study the potential impact of climate change on agriculture over the next two decades, because of questions he has received from stakeholders and decision-makers in governments and the private sector.

“I’m often asked whether climate change will threaten food supply, as if it’s a simple yes or no answer,” says Lobell. “The truth is that, over a 10- or 20-year period, it depends largely on how fast the Earth warms and we can’t predict the pace of warming very precisely. The best we can do is to attempt to determine the odds.”

Lobell and Tebaldi set out to estimate the odds that climate change could interfere with the ability of crop producers to keep up with demand. “Whereas other climate research had looked at the crop impacts that were most likely, Lobell and Tebaldi decided to focus on the less likely, but potentially more dangerous, scenario; that climate change would reduce yield growth by ten percent or more,” notes NCAR.

The authors also determined the correlation between warming temperatures and reduced yields. “For example, an increase in 1°C would slow corn yields by seven percent and wheat yields by six percent,” states the Atmospheric Research Institute.

“Depending on the crop-growing region, the odds of such a temperature increase in the next 20 years were between 30 and 40 percent, in simulations that included increases in carbon dioxide. In contrast, such temperature increases had a much lower chance of occurring in simulations that included only natural variability, and not human-induced climate change.”

The study warns that although society could offset the climate impacts by planting wheat and corn in cooler regions, such planting shifts, to date, have not occurred quickly enough to offset warmer temperatures. The authors also found little evidence that other adaptation strategies, such as changes in crop varieties or growing practices, would totally offset the impact of warming temperatures.

“Although further study may prove otherwise, we do not anticipate adaptation being fast enough to significantly alter the near-term risks estimated in this paper,” they conclude.