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Decreasing diversity in global food supplies threatens crop production and nutrition

As agricultural practices have evolved in recent decades, the total number of plant species grown for food worldwide has decreased. Diets have changed and become more Westernized. These trends have significant implications for the global food supply. In his 1975 book Crops and Man, Jack Harlan warned "more and more people will be fed by fewer and fewer crops."

farmers holding cassava roots

A recent study published in the Proceedings of the National Academy of Sciences examined how national food supplies have changed over the past 50 years for 98% of the world's population. Colin Khoury, a research scientist at the International Center for Tropical Agriculture in Cali, Colombia and lead author of the study, says, "Major staples such as wheat, rice, maize, and potato have become increasingly dominant in diets around the world." Overall, people are consuming more calories, fat, and protein, especially from meat and dairy, as well as oils and sugars.

Khoury notes that wheat and rice dominate diets in over 90% of all countries. Also, "some crops that were not globally important 50 years ago have risen greatly in importance. These especially include oil crops, such as soybean and palm oil."

As a result of these dietary changes, locally and regionally important crops have suffered. The study shows significant decreases in the importance of cereals like sorghum, millets, and rye. Starchy root crops like sweet potato, cassava, and yam have also declined. Although this decrease in crop diversity has happened around the world, "the changes in diets have been especially extreme in East and Southeast Asia, and in Sub-Saharan Africa," says Khoury. He observes that, over the time period studied, global diets increased in similarity by an average of 36%.

Khoury says, "Many contributing facets have moved the world toward 'Western' diets dominated by a few major crops." The study identified increases in wealth and purchasing power, globalization, urbanization, agricultural modernization, and development as major causes. These changes potentially threaten our food supply—as an ecological system becomes less diverse, it becomes more fragile and likely to fail.

bar graph showing change in diet

Human diets as a whole used to contain a greater variety of local and seasonal crops. Failures of any particular crop affected people locally but rarely affected humanity on the large scale. Once mass transportation allowed us to get food from one location to the other, season and geography became less important. People could “favor” one food over another. Now, we eat more of foods we prefer, versus what is available. Thus, if we like wheat, we eat more wheat. But, what if the wheat crops grown in major production regions and transported around the world were devastated by disease? Now a large part of our diet is at risk.

To address these problems, Khoury says, we will require a combination of scientific research, political agreements, and change in agricultural practices. "We need to ensure that the crops we absolutely depend on are genetically diverse." Resistance to disease, pests, and climate-related stress will be helped by growing many varieties with different characteristics. In addition, Khoury notes, "we need to ensure that the crops we increasingly depend on are nutritionally adequate."

Khoury observes that the decrease in crop diversity in diets may contribute further to higher rates of diabetes and heart disease. These major health concerns are already on the rise due to dietary changes. "These are diseases of overabundance," he says. "We need to promote healthier consumption patterns—how much we eat, what we eat, and how we eat."

The study concludes that it's not too late to make significant changes. It suggests that increasing awareness of healthy diets may help reverse current global trends of consuming more animal fat and protein. That, in turn, will affect the mix of important crops in food supplies. As Khoury says, "It could be very important to look at alternative crops that are resilient and invest in them to make them more productive. These crops may also be helpful in providing healthier alternatives in diets."