DR. Norman Borlaug's "Green Revolution" promised improved agricultural production and food security by creating and implementing relevant technologies throughout the developing world, transitioning agriculture from subsistence to commercial.
Researchers from the University of Minnesota and Canada's McGill University suggested that, in recent years, Borlaug's revolution has essentially withered on the vine.
A report published in the Dec. 18 issue of the journal Nature Communications on a study by those researchers found that yields have stagnated or fallen for key food crops in several regions of the world.
While developing and analyzing geographically detailed maps of annual harvested areas and yields for corn, rice, wheat and soybeans from 1961 through 2008, the researchers found that although virtually all regions showed a yield increase sometime during that period, in 24-39% of the harvested areas, depending on the crop, yields plateaued or actually declined in recent years.
Among the top crop-producing nations, significant areas of China and India are witnessing what the researchers described as an "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 as areas where yields are still rapidly improving," said Deepak Ray, a research fellow with the University of Minnesota's Institute on the Environment (IonE). "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."
Ray and his colleagues found that yields for two key food crops that provide roughly half of the world's dietary calories -- rice and wheat -- are declining across a higher percentage of acreage than yields for corn and soybeans.
"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," IonE director Jonathan Foley, a chaired professor in the University of Minnesota's College of Biological Sciences, said. "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 anymore?"
The article notes that while global demand for agricultural crops is expected to double by 2050 -- driven by increases in population, meat and dairy consumption and biofuel use -- crop production over the past 20 years has not kept pace. Between 1985 and 2005, total global crop production increased by 28%, based on a 2.5% net expansion of global cropland, a 7% increase in harvest frequency and an average 20% increase in crop yields per hectare.
Looking at the data, the researchers found that yields for the four crops studied never improved in a very small slice of the globe -- less than 1%. Those areas included outlying regions of U.S. production centers and developing areas of Europe and Asia (Figure). In most regions of the world -- between 61% and 76% -- yields continue to increase.
Globally, however, 35% of rice and 37% of wheat production areas have seen yield stagnation. These include many areas of the developed world, including soybean-producing regions of the U.S., wheat-producing areas in Europe and rice-producing areas of Japan.
In just 1-3% of the world's productive regions, yields have actually collapsed in recent years due partly to climate-related challenges. For example, wheat yields in Australia have dropped considerably as the country has dealt with a prolonged drought.
Discussing the reasons behind the observed yield trends, the researchers noted that both biophysical and socioeconomic causes play a role and are not necessarily mutually exclusive. In other words, climate change may play a role in Europe's wheat yield stagnation while those same weather patterns concurrently may lead to expanded wheat production in other regions.
Ray said the paper suggests two actions based on the research findings. First, it recommends working to maintain a positive trajectory for the 61-76% of cropland on which yields continue to increase. Second, it encourages producers to examine yield trends in crop-producing regions around the world to identify what's working and what might be improved.
"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 yield growth has stagnated or reversed, figure out what limiting factors are at play (and) then work to turn that trend around."