Thu, Dec 26, 2013 - Page 9 News List

Have we already reached ‘peak food’?

Most conventional yield projection models are oblivious to the real world, US researchers say

By Nafeez Ahmed  /  The Guardian

Illustration: Mountain people

Industrial agriculture could be hitting fundamental limits in its capacity to produce sufficient crops to feed an expanding global population, according to new research published in Nature Communications.

The study by scientists at the University of Nebraska-Lincoln in the US argues that there have been abrupt declines or plateaus in the rate of production of major crops, undermining optimistic projections of constantly increasing crop yields.

As much as “31 percent of total global rice, wheat and maize production” has experienced “yield plateaus or abrupt decreases in yield gain, including rice in eastern Asia and wheat in northwest Europe,” the study said.

The declines and plateaus in production have become prevalent despite increasing investment in agriculture, which could mean that maximum potential yields under the industrial model of agribusiness have already occurred.

Crop yields in “major cereal-producing regions have not increased for long periods of time following an earlier period of steady linear increase,” it added.

The paper makes for ominous reading. Production levels have already flattened out with “no case of a return to the previous rising yield trend” for key regions amounting to “33 percent of global rice and 27 percent of global wheat production,” the study said.

The US researchers concluded that these yield plateaus could be explained by the inference that “average farm yields approach a biophysical yield ceiling for the crop in question, which is determined by its yield potential in the regions where the crop is produced.”

They wrote: “We found widespread deceleration in the relative rate of increase of average yields of the major cereal crops during the 1990-2010 period in countries with greatest production of these crops, and strong evidence of yield plateaus or an abrupt drop in rate of yield gain in 44 percent of the cases, which, together, account for 31 percent of total global rice, wheat and maize production.”

Past trends over the last five decades of perpetually increasing crop yields were “driven by rapid adoption of green revolution technologies that were largely one-time innovations” that cannot be repeated.

These include major industrial innovations such as “the development of semi-dwarf wheat and rice varieties, first widespread use of commercial fertilizers and pesticides, and large investments to expand irrigation infrastructure,” it said.

Although agricultural investment in China increased threefold from 1981 to 2000, rates of increase for wheat yields have remained constant, decreased by 64 percent for maize and are negligible in rice.

Similarly, the rate of maize yield has remained largely flat despite a 58 percent investment increased over the same period.

The study warned: “A concern is that despite the increase in investment in agricultural R&D [research and development] and education during this period, the relative rate of yield gain for the major food crops has decreased over time together with evidence of upper yield plateaus in some of the most productive domains.”

The study criticizes most other yield projection models which predict compound or exponential production increases over coming years and decades, even though these “do not occur in the real world.”

It said that “such growth rates are not feasible over the long term because average farm yields eventually approach a yield potential ceiling determined by biophysical limits on crop growth rates and yield.”

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