Back to nature. An analysis of global land use and population growth has led Rockefeller scientists to conclude that use of land for farming has reached a peak, with former farmlands returning to nature. Above, land that was farmed and grazed in Chile is now returning to forest. Credit: Jesse H. Ausubel

(Phys.org)—With the global population racing past seven billion, demographers and world leaders have been concerned with depletion of resources to support everyone. The future, though, may be less bleak than some have feared. Changes in population growth and how farmers use land have brought the world to "peak farmland," a team of Rockefeller University scientists report in a special issue of the journal Population and Development Review.

"We are excited to report that we believe that humanity has reached peak farmland, and that a large net global restoration of land to nature is ready to begin," says senior author Jesse H. Ausubel, director of Rockefeller's Program for the Human Environment. "Happily, the cause is not exhaustion of arable land, as many have feared, but rather moderation of population and tastes and ingenuity of farmers."

Ausubel, with co-authors Paul Waggoner and Iddo K. Wernick, analyzed factors such as global land use and population growth over the last 50 years. Looking at the production index of all crops of the UN's Food and Agriculture Organization, they found that from 1961 to 2009 land farmed grew by only 12 percent while the index rose about 300 percent.

"Without lifting crop production per hectare, farmers would have needed about 3 billion more hectares, about the sum of the United States, Canada and China, or almost twice South America," says Ausubel. "The expanded cropland would have come at the expense of other covers, especially forest and grassland."

Using China as an example, Ausubel and his colleagues show that in 2010 China's maize farmers spared 120 million hectares from the land that would have been required with the yields of 1961, twice the area of France. Overall, the researchers found producing an equivalent aggregate of crop production in 2009 required only about 35 percent of the land needed in 1961.

In addition to improved yields achieved by farmers, the researchers credit additional factors leading to peak farmland: parents giving birth to fewer children, and consumers raising their calorie consumption more slowly than their affluence and moderating their meat eating.

"Our analyses over the past 20 years witness food decoupling from land," says Ausubel. "For millennia food production tended to grow in tandem with land used for crops, a fundamental relationship in population and development. Now land for food is flat. If yields had remained at prior levels, immense, continental areas of forest and range and desert would have been shaved and ploughed for human food during the past 50 years. Surprisingly, instead, we find humanity gradually moving toward what we call, with deliberate hyperbole, landless agriculture. We believe humanity now stands at peak farmland, and the 21st century will see release of wide areas of land, hundreds of millions of hectares—more than twice the area of France—for nature."

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