Producers grow wheat, rice, corn and soybeans on more than 50 percent of the world’s agricultural land
Human-caused changes in Earth’s biodiversity are well documented but a recent international study led by the University of Toronto looked at the impact of crops grown globally across 22 subcontinental-scale regions between 1961 and 2014.
The study suggested that not only are the same kinds of crops being grown but that they present major challenges for sustainability on a global scale.
Using data from the United Nations’ Food and Agriculture Organization, lead researcher Adam Martin, assistant professor in the U of T’s department of physical and environmental sciences, said farms are often growing just one crop species across thousands of acres.
The crops are wheat, rice, corn, and soybeans. These four alone occupy 50 percent of the world’s entire expanse of agricultural land, while the remaining 152 crops cover the rest.
The dominance of just four crops presents problems on a variety of levels.
“Having four major crops occupy more than 50 percent of global farms is problematic because extremely large expanses of agricultural lands are now virtually ecologically identical worldwide,” said Martin.
“These four crops in particular are widely acknowledged to be those grown in large monocultures where only a single crop species or genetic strain are cultivated under very high chemical inputs and irrigation systems.
“From a sustainability perspective, these crops represent those that contribute the largest to overall environmental impacts of industrial agriculture, including water consumption, greenhouse gas emissions, and declines in soil fertility. Their continued expansion represents a major environmental concern.”
The study recognized that crop diversity has increased in some regions. For instance, in North America 93 different crops are now grown compared to 80 in the 1960s. Even so, in North America six individual genotypes comprise about 50 percent of all corn crops.
Martin said that the four crops represent a disproportionately large amount of food consumed by people (about 75 percent according to some reports). When supplies for these foods drop due to weather-related yield reductions or diversion to biofuels (such as corn), overall food prices spike. As a result, the increasing production and reliance on these crops for food represent a major threat to food security.
The study documented that there was little change in crop diversity from 1961 to the late 1970s followed by a sharp diversification through the early 1980s and a levelling off of diversification beginning in the early 1990s.
“Our working hypothesis is that while the enactment of certain free trade agreements largely throughout the 1980s triggered new crops being grown, later on through the 1990s these same agreements started to favour a select few crops that could be grown at a major competitive advantage,” said Martin. “This may well have been the case with the North American Free Trade Agreement. We expect that in the lead up to NAFTA, new crops began to emerge in the Americas, which is consistent with our data. But later on, NAFTA clearly came to favour the cultivation and dominance of maize and wheat, perhaps at the expense of a more diverse set of crops. This is also consistent with our data.”
As a greater proportion of the world’s industrial farms look the same through monoculture cropping, choosing food that is culturally appropriate and produced through sustainable methods becomes more challenging.
“While food sovereignty still persists, particularly in more rural areas where connections with farmers are more direct, threats to food sovereignty are certainly emerging in more urban areas where these connections are now weakened,” said Martin. “There are also indications that food sovereignty is especially vulnerable in developing regions of the world. In North America, consumers can generally afford to purchase a variety of foods that are produced through sustainable means such as organic. However, in developing regions where a much larger proportion of household income goes toward food, a narrow range of cheaper imported food produced in industrial farms becomes increasingly the main source of food.”
He said that government decisions will also favour certain crops through crop-specific subsidies or policies such as supply management impacting how certain crops are favoured.