Is Climate Change Reducing Crop Yields?

Will the warmer temperatures and extra carbon dioxide that come with climate change improve plant growth? The answer is not forever. In fact, it’s possible we’ve reached a point where plant growth will actually decline globally due to climate change.

NASA scientists recently published a study in the journal Science showing that since 2000, global plant productivity declined by 1%. This decrease comes in spite of increased productivity in the Northern Hemisphere, particularly at higher latitudes, during that time. A drying trend in the Southern Hemisphere is counteracting these increases, though.

A 1% decrease might not sound like a lot, but it comes on the heels of a 6% increase of plant production between 1982 and 1999. This led many researchers to believe that climate change would continue to improve plant productivity for quite awhile into the future. In fact Steve Running, one of the researchers of the current study, stated:

"We see this as a bit of a surprise, and potentially significant on a policy level because previous interpretations suggested global warming might actually help plant growth around the world.”

However, it appears one of the few benefits of climate change may have already passed by. Even that benefit is a tenuous one. A study in June 2010 from University of California, Davis showed that increased atmospheric carbon dioxide can reduce grain protein content by up to 20%. So even the increased productivity climate change brings in the Northern Hemisphere can negatively impact the quality of our food.

The increase in productivity in the Northern Hemisphere doesn’t necessarily help people who rely most on agriculture and forests for subsistence either. The majority of those people live in the global South. If climate change continues to dry out crops and forests, a number of other issues arise.

First, subsistence farmers will have to plant more drought-resistant crops. There are major policy implications for governments that have large populations that fall into this category. For one, these crops, especially ones that are genetically modified (a whole other thorny issue), tend to be more expensive. Governments will have to help subsidize them to reduce the threat of food instability.

The other issue the study brings to mind is the competition between biofuels and food production. In countries like Brazil, which has an advanced sugar cane biofuels program and a large poor rural population, decisions will need to be made about how to balance the two opposing interests.

Add programs from the United Nations that look to pay countries to mitigate climate change using forests and you have three important, competing land management ideas that don’t always match up. If the decline in net plant productivity continues due to climate change or other factors, governments will be facing even more challenging decisions in the future. As one of the researchers Steve Running said in an interview:

“This is a pretty serious warning that warmer temperatures are not going to endlessly improve plant growth.”

The message is that now is the time to start planning for the worst case scenario.

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