"Changes in log yield if crop is exposed for one day to a particular 1◦C temperature interval..." Excerpted partial image and partial caption credit: PNAS, publication of Wolfram Schlenker and Michael J. Roberts, Supporting Information Appendix (pdf)
Most people realize that grain yields can fall when croplands are either continuously very wet or extremely dry, for extended periods. Futures market traders closely track weather reports and soil moisture at critical times of the year, knowing that changes in these can affect yield and, hence, prices on relatively short notice. Extreme US examples include: Upper Mississippi River floods eliminating yields over vast acreages; and, South Texas farmers losing hope of producing crops of any sort. What happens, though, when soil moisture is acceptable, but it's extraordinarily warm at critical times in the food crop's life cycle? Matt's post from August of 2009, US Corn, Cotton & Soybean Yields Could Decline Up To 82% Due to Climate Change, introduced us to a study documenting that hot days are significantly damaging to the named crops. Other science journals are taking notice; and I expect to see print and broadcast media reporting on this issue soon.
For example: New Scientist reports:
Wolfram Schlenker at Columbia University, New York, and Michael Roberts at North Carolina State University in Raleigh used a high-resolution dataset of weather patterns from 1950 to 2005 to discover how yields of three key US crops respond to increasing temperatures.The cited research was published by the NAS under the title - Nonlinear temperature effects indicate severe damages to U.S. crop yields under climate change Here is the money quote, excerpted directly from the Schlenker, Roberts paper abstract:
"The single best predictor of a year's yield is the amount of time temperatures exceed about 29 °C and the extent to which they do so," they say. "Below this, warmer temperatures are beneficial for yields, but the damaging effects above 29 °C are staggeringly large."
Holding current growing regions fixed, area-weighted average yields are predicted to decrease by 30-46% before the end of the century under the slowest (B1) warming scenario and decrease by 63-82% under the most rapid warming scenario (A1FI) under the Hadley III model.
Comments and extrapolations:
Changes such as those projected by the cited authors won't occur uniformly across nations, or even across agronomic regions. Analogous to drought or flood losses, the impacts of hot weather on crop yield will come and go, perhaps with a seemingly random characteristics. The projected impact on commodity grain prices and availability will be visible to professionals, however. Increasingly so, as climate change results in more severe and widespread weather extremes (which at times means excessive heat, as well as cool weather extremes).
The impacts won't hit just US commodity prices and food availability. Subsistence corn growers in subtropical and tropical countries such as Mexico and Kenya, respectively, will be directly affected as well, unseen by commodity traders until food aid is arranged.
Expect prices of corn-based ethanol and corn syrup to rise rapidly at times, in response to heat-wave caused yield drops, and as increasingly large portions of US grain production is diverted to corn chips and emergency food aid shipments, for example.
The US Farm Bureau, always a conservative organization, is currently actively lobbying against Cap & Trade provisions of a US climate bill...against their heirs interest; per the cited research! However, I find it hard to believe that the agribusiness professionals who pay close, analytical attention to the 'big picture' are unconcerned about the sustainability of their business model.
Where's the outrage? And, the testimony in support of a strong climate bill?
When do commodity grain traders and distributors testify before Congress, in active support of climate action? One can easily understand Nike Corporation pulling out of the US Chamber of Commerce in order to maintain a green corporate image with the heavily young market of electronics buyers.
Cash crop yield is a key factor in agribusiness raw material pricing This includes food processors and fast food brands that use grains as major ingredients. When do we hear from them? Even bottlers. Do they not see the coming risk of corn syrup price increases constantly eroding profits?
More posts on grain yield and climate change.
Could Food Shortages Bring Down Civilization?
Common BioFuel Myth: Corn-Based Ethanol To Blame For Global Food Shortages
Why GMO Foods Have Failed at Producing Healthy Food for More ...
Stop Crying Wolf! Cap-and-Trade Will Increase Farmer's Production Costs Less Than 1%