U of T-led study finds global crop diversity on the decline

Aerial photo of a combine harvesting a wheat field
The study, led by U of T Scarborough's Adam Martin, tracked crops on large-scale farmlands around the world between 1961 and 2014 (photo by Christian Ender via Getty Images)

A new University of Toronto study suggests we’re growing more of the same kinds of crops around the world, presenting a major challenge to agricultural sustainability.

The study, undertaken by an international team of researchers led by U of T Scarborough’s Adam Martin, used data from the U.N.’s Food and Agricultural Organization to look at which crops were grown where on large-scale industrial farmlands from 1961 to 2014.

While they found crop diversity within specific regions has increased – in North America for example, 93 different crops are now grown compared to 80 back in the 1960s – Martin says that, globally, we’re now seeing more of the same kinds of crops grown on much larger scales.

In other words, large industrial farms in Asia, Europe, North America and South America are all beginning to look the same. 

“What we’re seeing is large monocultures of crops that are commercially valuable being grown in greater numbers around the world,” says Martin, who is an assistant professor in U of T Scarborough’s department of physical and environmental sciences.

“So large industrial farms are often growing one crop species, which are usually just a single genotype, across thousands of hectares of land.”

Soybeans, wheat, rice and corn are prime examples. These four crops alone occupy just shy of 50 per cent of the world’s entire agricultural lands, while the remaining 152 crops cover the rest.

It’s widely assumed that the biggest change in global agricultural diversity took part during the so-called Columbia exchange of the 15th and 16th centuries – when commercially important plant species were transported to different parts of the world.

But the study’s authors found that in the 1980s there was a massive increase in global crop diversity as different types of crops were grown in new regions on an industrial scale for the first time. By the 1990s, however, the growth in diversity flattened out and has since declined.  

The lack of genetic diversity within individual crops is pretty obvious, says Martin. For example, in North America, six individual genotypes comprise about 50 per cent of all maize (corn) crops.

The decline in global crop diversity is an issue for a number of reasons. For one, it affects regional food sovereignty. “If regional crop diversity is threatened, it really cuts into people’s ability to eat or afford food that is culturally significant to them,” says Martin.

In addition, Martin says if there’s increasing dominance by a few genetic lineages of crops, then the global agricultural system becomes increasingly susceptible to pests or diseases. He points to a deadly fungus that continues to devastate banana plantations around the world as an example.

Martin hopes to apply the same global-scale analysis to look at national patterns of crop diversity as a next step for the research. He adds that there’s a policy angle to consider, too, since government decisions that favour growing certain kinds of crops may contribute to a lack of diversity. 

“It will be important to look at what governments are doing to promote more different types of crops being grown or, at a policy-level, are they favouring farms to grow certain types of cash crops,” he says.

The study, published in the journal PLOS ONE, received funding from the Natural Sciences and Engineering Research Council of Canada, among others. 

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