Study shows yields have plateaued or dropped in many places for world's most important crops

December 18, 2012
Detailed analysis of maize (corn) yields around the world show a disconcerting stagnation or collapse in many locations since the heyday of the Green Revolution. Credit: Deepak Ray, Institute on the Environment.

The Green Revolution has stagnated for key food crops in many regions of the world, according to a study published in the Dec. 18 issue of Nature Communications by scientists with the University of Minnesota's Institute on the Environment and McGill University in Montreal, Canada.

Led by IonE research fellow Deepak Ray, the study team developed geographically detailed maps of annual crop harvested areas and yields of maize (corn), rice, wheat and soybeans from 1961 to 2008. It found that although virtually all regions showed a yield increase sometime during that period, in 24 to 39 percent of the harvested areas (depending on the crop) yield plateaued or outright declined in recent years. Among the top crop-producing nations, vast areas of two of the most populous – China and India – are witnessing especially concerning stagnation or decline in yield.

"This study clearly delineates areas where yields for important food crops are stagnating, declining, or never improved, as well areas where yields are still rapidly improving," Ray says. "As a result, it both sounds the alert for where we must shift our course if we are to feed a growing population in the decades to come, and points to positive examples to emulate."

Interestingly, the researchers found that yields of wheat and rice – two crops that are largely used as , and which supply roughly half of the world's dietary calories – are declining across a higher percentage of cropland than those of corn and soybean, which are used largely to produce meat or biofuels.

"This finding is particularly troubling because it suggests that we have preferentially focused our efforts on feeding animals and cars, as we have largely ignored investments in wheat and rice, crops that feed people and are the basis of in much of the world," said study co-author and IonE director Jonathan Foley, professor and McKnight Presidential Chair in the College of Biological Sciences. "How can we meet the growing needs of feeding people in the future if one-third of our cropland areas, in our most important crops, are not improving in yield any more?"

The paper suggests two actions based on its findings. First, it recommends working to maintain the positive trajectory for the 61 to 76 percent of where yield is still climbing. Second, it encourages crop-producing regions around the world to look at their yield trends and those of others to identify what's working and what might be improved.

"Previous research suggests that many factors work together to limit yield growth, from cultivation practices to pests to a need for improved seeds," Ray said. "What this paper does is provide concrete, detailed information policy makers can use to identify regions where growth has stagnated or reversed, figure out what limiting factors are at play, then work to turn that trend around."

Explore further: Pollinator decline not reducing crop yields just yet

More information: … full/ncomms2296.html

Related Stories

Pollinator decline not reducing crop yields just yet

November 10, 2008

( -- The well-documented worldwide decline in the number of bees and other pollinators is not, at this stage, limiting global crop yields, according to the results of an international study published in the latest ...

Improving wheat yields for global food security

July 25, 2011

With the world’s population set to reach 8.9 billion by 2050, CSIRO scientists are hunting down and exploiting a number of wheat’s key genetic traits in a bid to substantially boost its grain yield.

Recommended for you

Finding a lethal parasite's vulnerabilities

December 15, 2017

An estimated 100 million people around the world are infected with Strongyloides stercoralis, a parasitic nematode, yet it's likely that many don't know it. The infection can persist for years, usually only causing mild symptoms. ...


Adjust slider to filter visible comments by rank

Display comments: newest first

3.3 / 5 (7) Dec 18, 2012
I willfully deny that this is happening and choose to live in a reality where crop yields will continue to grow exponentially forever.

The rest of you can starve if you like. I will never do so in my reality.

3 / 5 (2) Dec 18, 2012
"This finding is particularly troubling because it suggests that we have preferentially focused our crop improvement efforts on feeding animals and cars, as we have largely ignored investments in wheat and rice, crops that feed people and are the basis of food security in much of the world,"

Using crop lands for biofuels for cars never made any sense to me. It serves only to increase food prices, and it is not renewable, because eventually the soil is going to be depleted of nutrients. so "biofuels" are not sustainable, because we will deplete the continental food production much more quickly over decades or generations compared to farming for human food and livestock feed only.

Further, direct solar harvesting for electricity is more efficient than biofuels anyway, I think somewhere between 3 and 6 times more efficient.

I've also considered the hydrogen storage problem, and the easiest way to store hydrogen is as Methane, since it's a larger molecule.
3.7 / 5 (3) Dec 18, 2012
It may seem silly at first, but pure hydrogen is too hard to store because it escapes too easy. Containers require meta-materials and nano-technolgy.

Methane, CH4, the primary component of natural gas, has been stored forever in common tanks.

So if anything, an artificial, solar powered synthesis of Methane as a storage medium would be better than hydrogen just because it would be lower tech, and therefore cheaper.

Mankind made 35 billion tons of of CO2 last year. now 12/44 times 35 billion tons is 9.55 billion tons of carbon. Which is like burning an adult tree for every person on Earth...every year...

If not for the nuclear and hydro power and the spattering of wind and solar power we already use, we'd probably be making 2 or 3 times as much CO2 per year.

While Methane is not as low in carbon as hydrogen itself (which is zero,) by the time you count other costs, Methane may actually be "cleaner". It's certainly a lot less carbon per unit energy than say gasoline or diesel.
5 / 5 (1) Dec 18, 2012
@VD: And of course in your world population and so demand increase exponentially too, to explain the production.

Happily in our world that has proven not to be the case. Population will likely top out in the 30's - 40's.

We also don't demand crops to stay the same. As in all technology, exponential increase in efficiency comes out of production changes.

For example, Venter's synthetic bacteria proposal for simple nutrients and fuels (at first) can radically increase efficiency, and even utilize ocean areal instead of cutting into land food production.
1 / 5 (1) Dec 18, 2012
@Lurker - I like the cut of your jib, however presumably the methane would then require combusting to release its energy, producing water and CO2... whereas solar-powered hydrogen cuts carbon out completely..

Then again, crops like CO2 and water...
not rated yet Dec 19, 2012
The researchers who understand reality, and are (usually) employed in industry so they don't have to apply for grants from the funny farm in Washington (or other capitals) know that there are three major contenders for fueling fuel-cells: methane, methanol (wood alcohol), and ethanol (the alcohol you drink). Current regulations in most areas make (relatively) pure ethanol unlikely as a fuel. (In fact getting the last 4% of water out is a bitch and would never be done for fuel cell purposes anyway. But I digress.)

My expectation is that the final choice will be an ethanol/methanol blend. Easy to make from biomass by destructive distillation, and more important easy to purify, filter, transport and store. (It is a liquid, and much nice than gasoline to work with.)

The ratio of carbon to hydrogen should be a non-issue. There are fuel cells that work on all three fuels and consume the carbon. Yes, that puts CO2 back in the air, but the keyword is back.

1 / 5 (1) Dec 19, 2012
The best way to make fuel without using our food supply is to make fuel from waste. There is so much waste out there that isn't being utilize. We need to stop growing crops for biofuels unless its a crop that's inedible like algae or growing bacteria in a biovat.
1 / 5 (1) Dec 19, 2012
Great job guys. Let's argue about fuels and fuel cells while the real problem is over population. We're headed down a path that could turn out to be quite disastrous. All it would take would be a volcanic eruption that blocked a good percentage of the solar energy reaching earth and crop yields would be slashed. Then what? Do I need to explain what the world would be like if 1st world nations had millions of starving citizens?
The world is a finite space and I for one am not interested in altering my diet or lifestyle so that some greedy, brain dead people can have 19 kids and counting. Nor am I willing to accept to risk associated with overpopulation just because people are too stupid to recognize the danger. Growing food in the ocean? You do realize that a whole ecosystem is using that space right? That ecosystem which has provided food for eons is already on the verge of collapse due to over-harvest and pollution and you want to add new stress?
3 / 5 (2) Dec 19, 2012
If we run out of food it will make fuel shortages and global warming seem like a minor inconvenience.
4 / 5 (2) Dec 23, 2012
The world in not a finate space there is always up.
not rated yet Dec 23, 2012
JimCool thinks that if someone stands on his head the world will magically increase the amount of sunlight it receives, and hence increase the net productivity of the biosphere.

Why he thinks such foolish things is a mystery to me.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.