Peak farmland? The landscape of the future has more wilderness.

• Author: Bailey, Ronald
• Position: Trends in agricultural productivity - Column

"HUMANITY NOW STANDS at Peak Farmland, and the 21st century will see [the] release of vast areas of land, hundreds of millions of hectares, more than twice the area of France, for nature," declared Jesse Ausubel, director of the Program for the Human Environment at Rockefeller University, in a December lecture. Ausubel was outlining the findings of a study he and his collaborators had reported in the Population and Development Review Supplement that month. Unlike other alleged resource "peaks," peak farmland reflects not the exhaustion of resources but the fruits of human intelligence and affluence.

The trend toward reducing farming's impact on nature took off with the Green Revolution of the 1960s.That leap in agricultural productivity was sparked by plant breeder Norman Borlaug and his colleagues, who created high-yield varieties of wheat and rice, an effort so successful that Borlaug received the Nobel Peace Prize in 1970.

While Borlaug was working to avert famines, others were declaring them inevitable. "The battle to feed all of humanity is over," Stanford biologist Paul Ehrlich declared in his best-selling 1968 dystopian screed The Population Bomb. "In the 1970s the world will undergo famines--hundreds of millions of people are going to starve to death in spite of any crash programs embarked upon now." The epicenter of Ehrlich's alarm was impoverished India.

In 1960 India's population was 450 million, and the average Indian subsisted on a diet of just over 2,000 calories per day. Indian farmers wrested those meager calories from 161 million hectares (400 million acres) of farmland, an area a bit more than twice the size of Texas. By 2010 the Indian population was more than two and half times as big, national income had risen 15-fold, and the average Indian ate one-sixth more calories. Yet the amount of land devoted to crops rose just 5 percent, to 170 million hectares.

Had wheat productivity in India remained the same as it was in 1960, Ausubel and his colleagues calculate, farmers would have had to plow up an additional 65 million hectares of land, an area one and a half times the size of California. Instead, as people abandoned the land for cities, Indian forests expanded by 15 million hectares--bigger than the area of Iowa.

This trajectory of rising agricultural productivity has also been seen in post-Mao China. During that period, China's population doubled, and its GDP rose 45-fold.While the amount of land harvested for corn also...