Asian Rice Yields Drop As Climate Change Warms Nighttime Temperatures

rice fields in bali photo

photo: @marco via flickr

Just as Lester Brown writes about rising temperatures leading to rising food prices, a new report in the Proceedings of the National Academy of Sciences details the connection, already evident and likely to become more so, between rising temperatures and declining rice yields in parts of Asia. It's decidedly not a pretty picture.Examining statistics from 227 farms across six important rice-producing countries in Asia, a team of researchers led by Jarrod Welch of the University of California, San Diego found that rising temperatures have significant effects on crop yields.

As daily minimum temperatures rise (as in, nights don't get as cool) rice yields drop. Data from the Philippines shows yields declining 10% for every 1°C increase in daily minimum temperatures.

On the other end of daily temperature, higher maximums increase crop yields, but only to a certain point after which yields decline. Even when higher maximums increase yields though, this benefit is less than the negative impact of less cool nights.

BBC News quotes Welch:

We see a benefit of [higher] daytime temperatures principally because we haven't seen a scenario where daytime temperatures cross over a threshold where they'd stop benefiting yields and start reducing them.

There have been some recent studies on US crops, in particular corn, that showed the drop-off after that threshold in substantial.

The report concludes that future warming implies "a net negative impact on yield from moderate warming in coming decades. Beyond that, the impact would likely become more negative."

Read the original report: Rice yields in tropical/subtropical Asia exhibit large but opposing sensitivities to minimum and maximum temperature
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More on Global Warming & Agriculture:
Rising Temperatures, Rising Food Prices
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