NextBillion - An Initiative of the William Davidson Institute at the University of Michigan

Thursday, November 5, 2015

Science has made huge progress in improving the productivity of plants. Through breeding to increase the edible parts of crops, planting in new arrangements, and by developing new fertilizers and pesticides, scientists have helped feed ever more people. The Green Revolution in the 1950s and ’60s doubled and quadrupled yields of wheat, rice, and other crops around the world, and we’ve seen productivity increases ever since.

The question now is how science continues to make improvements as the global population grows, and demand for food keeps rising. We will need 70% more calories globally by midcentury, according to U.N. estimates.

Stephen Long, a plant scientist at the University of Illinois, says techniques developed during the Green Revolution are hitting their limits. For example, you can’t keep increasing the edible portion of individual plants “because you’ve still got to have some stems and leaves and structure to hold the grain,” he says. “Sixty to sixty-five percent is about as far as you’re going to get with that strategy.” (Wheat looks dramatically different today, with bigger ears.)

Yield increases—the amount of a plant you can grow in one space—are now flattening out, too. A recent analysis from University of Nebraska–Lincoln found that 30% of major cereal crops, like corn, wheat, and rice, have reached their “maximum possible yields.” And we know that continued use of heavy “inputs” like nitrogen fertilizer (a key part of the Green Revolution) are harmful to soil quality and often injurious to the wider environment.

“If we look at current rates of yield improvement globally, we’re going to come nowhere near that [required 70%] percentage increase. So we really need new ideas and breakthroughs,” Long says.

Long and others are looking to the fundamental molecular machinery of plants, particularly the way plants convert sunlight and carbon dioxide during photosynthesis. Long thinks this process is the best opportunity left to improve plant sizes and thus raise crop productivity. If you can’t increase the relative size of what’s edible in a plant, he says, you need to work on its absolute size, and that means getting into the guts of how plants grow.