For anyone that hasn’t been paying attention to how fast food prices are rising, and why, this week’s new report published in Science will come as news. You know that canard about how rising CO2 levels will help us grow more crops? Turns out, not so much…
Science Magazine reports:
“It’s a frustration having to always answer questions about the future and having everyone think of climate change as something in the future,” says David Lobell, an agricultural scientist at Stanford University in Palo Alto, California. “It’s not something we have to anticipate. It’s something we have to learn from and deal with right now.”
Lobell and colleagues analyzed agricultural records of corn, rice, wheat, and soybeans from 1980 to 2008. Those four crops make up 75% of the calories consumed by the world’s population. Using historical weather data on temperature and precipitation, the researchers constructed a trend line of weather patterns, controlling for a certain amount of seasonal variation, and linked it to crop data year by year. They also constructed a second trend line that assumed no warming during the period, and then compared the two.
Worldwide, the authors report online today in Science, yields of corn and wheat declined by 3.8% and 5.5%, respectively, compared with what they would have been without global warming. Rice and soybean production remained the same. But the trends vary considerably from region to region. Unlike most other regions, the United States and Canada saw no climate-linked decline in food production during this period. Lobell says that this is consistent with data from the Intergovernmental Panel on Climate Change (IPCC) showing that the eastern part of the United States has not warmed as much as other parts of the world for unknown reasons.
The most surprising finding, Lobell says, was how widely temperature trends varied by region and how dramatically they affected crop production. Rainfall, by contrast, seemed to contribute little to agricultural production trends. Although new technology and better farming practices have led to an overall increase in productivity, Lobell says, this increase isn’t keeping pace with warming. As the group reports in the paper, a rise in temperature of 1°C tends to lower yields by 10% in countries that aren’t at high latitudes.
There is lots of published peer reviewed science on this topic but here is the “coles notes” explanation: higher levels of atmospheric CO2 cause some plants to increase the size of their stalks (inedible material) while they decrease the size of their leaves. The explanation is simple: plants pull in CO2 though openings called stomata but this is also the place where plants loose water. So when a leaf is growing in higher levels of atmospheric CO2, plants adapt by creating a lower number of stomata.
To learn more, just Google these phrases:
stomata co2 response
“spencer weart” stomata
In his book “Climate Wars”, author Gwynne Dyer states on page 50 “while rice will germinate at temperatures as high as 45 degrees Celsius, most of the grains will be sterile if the temperature remains above 36 C fore more than a few hours during anthesis (the most critical part of the flowering cycle) and many countries already experience these temperatures”
Failure to flower will mean starvation for many people dependent upon rice.