For me, the security of our food supply is one of the most significant of all the climate change impacts. Food shortages lead to famine which leads to mass migration and conflict. It is therefore important to predict how the warming planet will affect the yields of crops that we eat.
A paper published this week in Nature Climate Change finds that without adaptation, crop yields for wheat, rice and maize will start to decline from the 2030s onwards with the greatest impact in the second half of the century. This is much earlier than previously thought.
With adaptation however, these losses can be mitigated, particularly for rice and wheat, less so for maize. Adaption refers to changing farming practices to suit the new climate. This includes things like using different plant varieties, changing planting times, irrigation and also by changing crops altogether.
I’ve taken the following image from the paper. It shows crop yields for maize, wheat and rice in both tropical and temperate regions and the impact of temperature up to 5°C, with and without adaptation (click to view a larger version).
What does this mean? The yields of all three crops decline as the temperature increases. With adaptation, though, these losses can be mitigated and in some cases reversed. Wheat performs best with adaptation in temperate regions and rice does best with adaptation in tropical regions. Adaptation seems to make little difference for maize in both temperate and tropical regions.
The Working Group II IPCC assessment is due to be released at the end of this month and its focus is on impacts, adaptation and vulnerability. The last Working Group II assessment was in 2007 and the outlook for crop yields has worsened since that report. The results of this paper will be a part of this next assessment.
What this paper highlights for me is how increasing temperatures are not necessarily good for the plants we eat and also how important adaptation is going to be.