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When it comes to the future of human life on Earth, there's no more basic question than will there be enough food for everybody? Well, a group of scientists just took a fresh look at that question, and their conclusions are both comforting and disturbing. NPR's Dan Charles with our Planet Money Team has this report.

DAN CHARLES: Before Jonathan Foley became an expert on global food production at the University of Minnesota, he was an astronomer.

Dr. JONATHAN FOLEY: So, you know, take an astronomer and have him think about farming, and this is what you get.

CHARLES: What you get is a look at farming on the whole planet as if you were staring at Earth from outer space. When you do that, the thing that jumps out at you, Foley says, is this: Pretty much, the single most destructive thing that we humans do to our planet is grow food.

FOLEY: Agriculture and our croplands and pastures uses up 40 percent of all the land on Earth. It's 70 percent of the water being consumed on the planet. It's about a third of all the greenhouse gas emissions.

CHARLES: That's shocking. A third of all greenhouse gases, you say, are coming from farming?

FOLEY: Conservatively, a third. Probably more.

CHARLES: And then you realize it's going to get worse. Another two or three billion people are coming. Plus, a lot of people are getting richer, which means they eat more. And they eat more meat, which in turn means you have to grow even more crops to feed those animals.

FOLEY: It turns out that we would have to double the world's food supply by 2050 to keep up with that demand.

CHARLES: Double the world's food supply?

FOLEY: That's right. What it took 10,000 years to build up to, we have to double in the next 40 years or less.

CHARLES: Foley and a group of collaborators from around the world took a close look at whether this is even possible. In a study released today by the scientific journal Nature, they say it is, if we do five things. First, stop cutting down forests to grow crops. Second, instead of that, focus on land that's already being used to grow food but isn't very productive.

FOLEY: Eastern Europe, for example, is not producing much food right now, but it could. Much of Africa could be growing much more food than it is today.

CHARLES: An average acre of land in Africa currently produces only about a sixth as much grain as an acre in Illinois. Third, use water more efficiently, also fertilizer. Fourth, in rich countries, don't throw away so much food. In poor countries, keep it from spoiling before it gets to the people who need it. Fifth, and this may be the most controversial thing in this paper, eat less meat.

Right now, a third of all crops in the world go to feed cattle, chickens and pigs. If we do all that, Foley says, there will be enough food for everybody, and we won't have to destroy even more of our planet. But we really do need to do all that.

FOLEY: It is impossible to keep feeding the world the way we are and do it sustainably. You know, if we're going to feed the world and sustain the environment, we have to get on this path.

CHARLES: Now, Foley gave a presentation on this topic recently to an academic audience. And Thomas Hertel from Purdue University got up and said, basically...

THOMAS HERTEL: What about economics?

(SOUNDBITE OF LAUGHTER)

CHARLES: Hertel says the problem with this paper is it doesn't really show us how to get on this different path.

HERTEL: It's all well and good to tell people they shouldn't consume meat. But in the end, consumer preferences will prevail. And that's what's driving the increased production of some of the feed grains.

CHARLES: Farmers all over the world grow whatever earns them the most money. Hertel says economic forces created the kind of farming we have today, and the trick will be to use those same economic forces to help change it.

For instance, taxes or regulations can make it really expensive to clear forests for agriculture or to overdose fields with fertilizer. But when it comes to figuring out how to grow enough food to feed everybody or decide how much grain gets fed to animals instead of directly to people, it's still going to come down to markets, he says. Supply and demand. When food gets scarce, prices do rise, and farmers respond by growing more.

Also, they'll be motivated to do a couple of things on Foley's list: Get more productive and more efficient. Dan Charles, NPR News.

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