Researchers in the United States have come to the conclusion that 'peak farmland' has been reached worldwide, and that from now on the amount of the Earth's surface used for agriculture will decline.

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Although the concept of 'peak farmland' is normally used in a bleak context, associated with the point at which the earth will no longer be able to support its human population adequately, the scenario envisaged by the American researchers is actually a positive one.

On Monday, scientists from New York's Rockefeller University announced that an area twice the size of France may be able to return to a more natural state as increased yields and decelerated population growth reduce the burden on farmland. Their optimistic assessment stands in contrast to more Malthusian projections put forward by the United Nations and backed by industry and environmentalists alike.

Although UN figures show increased demand from the biofuel and livestock industries, twinned with the effects of climate change and shifting consumption patterns will increase pressure on farmland, possibly meaning more land will be converted to grow food and fuel by the middle of the current century, the Rockefeller team suggest otherwise.

The researchers predict an astounding 10 percent of the arable land currently in use could be returned to a more natural state by 2060. Jesse Ausubel, director of the university's Program for the Human Environment and lead author of the Rockefeller study, said that improved yields, new technologies and innovation at farm level would ease pressure and free up land. He based his assessments on figures from the rapidly growing economies of India and China.

However, although some commentators have said the reports' predictions are possible, they added that improvements predicted by Ausubel and the Rockefeller researchers would be dependent on new technologies being made available around the world, and on supporting and empowering people to improve yields in other global regions.

Although the Rockefeller report's authors predict 150 million hectares could be returned and allowed to regenerate by 2060, FAO figures released earlier this year claim over 70 million hectares of extra land will be needed to feed the global population by the same date.

Ausubel admits that water stresses, a changing climate, shifting patterns of meat consumption and an increase in biofuel production could all potentially affect his predictions, though he said meat consumption is increasing at only half the rate of affluence. The Rockefeller report also shows production of non-food crops, such as biofuels and bioenergy feedstocks, cotton and tobacco, is expected to outstrip increases in food production towards the middle of the century.

Furthermore, in addition to basing his predictions on assumptions about the growth of biofuels and effects of climate change, Ausubel's consumption data is balanced against GDP figures, which may increase while real incomes for the majority in a given country decline. The China Household Finance Survey, released last week, showed China has a significant level of income inequality, although the country's GDP is increasing.

Nevertheless, commenting on his report on Tuesday (18th December) in New York, Mr Ausubel said, "20 years ago… I observed the pervasiveness of projections of unremitting deforestation, owing largely to extension of agriculture, and… asked the question, 'How much land can 10 billion people spare for Nature?' [However, I] calculated that large expanses of land could be spared if population growth slowed, tastes changed, and yields continued rising."

However, Ausubel believes the area of land used for farming is currently at its apogee, and land is ready to be released. He said, "Happily, the cause is not exhaustion of arable land, as many have feared, but rather moderation of population and tastes and ingenuity of farmers."

Concluding optimistically, he said, "Importantly, sparing land usually means sparing water. And substituting bits or information in Precision Agriculture can also spare inputs of energy and nitrogen and other materials. Precision agriculture includes better weather forecasts, closer spacing of plants, better and more judiciously applied fertilizers, smart farmers… Land spared can become habitat for wildlife or carbon orchards."

The full Rockefeller report, Peak Farmland and the Prospects for Sparing Nature, is available here.