Global warming will cut crop harvests by 2% each decade, researchers say

Decline in predicted crop yields is larger than first thought and could endanger food security, unless CO² emissions are cut
Oliver Milman 19 Mar 14;

Wheat field Australia Wheat harvests in tropical areas will be among those crops most affected with yields declining by 40% under modelling by researchers. Photograph: Simon Freeman/AAP/Grain Corp

Climate change will cause bigger falls in crop yields than previously thought, exacerbating food insecurity, a new study has found.

The research, conducted by Australian, British and American scientists, found that the situation will worsen in the second half of the century, with tropical areas worse hit than temperate regions.

An analysis of more than 1,700 simulations found that across all regions and all crops, including wheat, maize and rice, yields will drop by 2% each decade, based on a 2C rise by 2050.

However, for some crops, the situation will be much worse, with wheat and maize in tropical areas experiencing a 40% decline if temperatures reach 5C warmer than pre-industrial levels.

Governments have agreed a target of limiting temperature rise to 2C above pre-industrial levels, although scientists warn the planet could experience a 4C or even 5C rise if carbon dioxide emissions are not drastically cut.

The report’s co-author Dr Mark Howden, of the CSIRO, said the situation was worse than previously thought.

“We looked at a whole range of temperature and rainfall scenarios and found results that were distinctly far more negative than the previous IPCC report,” he said.

“The impacts are consistently negative beyond 2C of warming. There will be greater and greater impacts upon crop yields in future decades. Maize is the most sensitive, but also crops grown in tropical environments such as wheat and rice.”

Howden said countries already expected to suffer food insecurity due to climate change will be the worst hit by yield declines, with rising temperatures causing more damage than changes to rainfall patterns.

In Australia, a lack of rainfall will be the biggest issue for many farming areas, with a hotter, drier climate causing more variable, lower yields.

Howden said adaption to these trends, such as changing planting times and irrigation, could produce a 10-15% increase in global yields compared to no action, providing food to 500 million to 1 billion people around the world.

However, with increased consumption and population growth will require a 14% increase in yields per decade, a target Howden said would be “far more difficult” with climate change.

“We have to work on the adaption path, so manage the climate we will expect rather than the one we currently have,” he said.