How do you feed 9 billion people without destroying the planet?

Transform the global food system in the next 40 years by using crops to feed people instead of fattening livestock and producing fuel; eliminate food waste; and overhaul the use of fertilizers like nitrogen that are polluting waters around the world.

Those are some of the conclusions in a study led by a University of Minnesota researcher published online Wednesday by the journal Nature. It provides a snapshot of the perilous state of the world's food system -- and how it has changed the face of the planet.

Though the problems described in the paper have been well documented, the study takes the unusual approach of suggesting solutions for all of them simultaneously.

"We wanted to address food and environmental problems," said Jonathan Foley, the lead author. "Up until now they've been treated as separate."

Unlike some academic research, the paper is getting national attention, and Foley has been making his case in meetings with food industry executives at corporations such as General Mills and Cargill, and international environmental and agricultural groups.

How to feed the world without destroying the planet "is a critical question that everyone in this industry is trying to grapple with," said Jerry Lynch, vice president of sustainability for General Mills. The paper is "a good analysis that helps crystalize the challenge and the potential strategies."

Others, however, said the study ignored one of the most fundamental realities of agriculture -- the economic structure of the food industry.

"Our food system is largely fashioned to benefit the largest industrial agriculture interests, and runs directly contrary to a sustainable and healthy food system," said Adam Warthesen, policy manager for the Land Stewardship Project.

Foley said he started the research a few years ago while analyzing satellite photos of land change for the National Aeronautic and Space Administration. The images showed tens of thousands of acres of forests and grasslands disappearing, all of it converted to cropland, he said.

For the past two years Foley and a team of 20 scientists from around the world compiled and analyzed international production data to reveal a troubling picture of agriculture.

Today it takes up 38 percent of the earth's surface, the study found. Virtually every acre of land that is suited for farming is now being farmed. Worldwide, 70 percent of the grassland, 45 percent of deciduous forests and 27 percent of the tropical forests have been converted to agriculture.

Some regions of the world, like Africa, don't have nearly enough fertilizer, while others like the United States and China use far too much.

A billion people are starving or malnourished, while another billion are overweight or obese. The population is expected to grow to 9 billion or 10 billion the coming four or five decades, which will require a doubling of food supplies.

"We can't keep doing this," Foley said simply.

New thinking

The team came up with a strategy to double the world's food production while reducing the environmental effects of agriculture.

First, use financial incentives and economic development to stop the conversion of forests to farmland, the paper says. Growth in the food supply must come from improving yields where they are low -- India, Eastern Europe and Africa.

Today, more than a third of the world's cropland is dedicated to growing feed for animals and to biofuels. Add pastures to that "and we find the land devoted to raising animals totals ... an astonishing 75 percent of the world's agricultural land," the study said. Devoting more cropland to human food production could boost calories produced per person by nearly 50 percent.

Reducing food waste, from farm to table to garbage can, could boost supplies by a similar amount. Grazing should be promoted on land that is unsuitable for crops, the study suggested.

Foley said he recognizes that the "30,000 foot view" presented by the paper may seem impractical. But not entirely. For example, 40 percent of nitrogen pollution comes from 10 percent of the world's farms -- a manageable problem, he said. Ending the destruction of forests in two countries, Brazil and Indonesia, would have an immediate impact on climate change, he added.

"We don't have to solve every problem everywhere," he said.

Josephine Marcotty • 612-673-7394