Researchers have assembled a new model designed to help calculate the effect of a human reaction to climate change on a land's agricultural utility.

Humans have responded to shifting climates throughout the millennia, whether it be the Mayans moving away from key ceremonial centers due to drought, or the much more recent migration of individuals living in Burkina Faso in West Africa from the drought-ridden north to the south. In both instances, the arrival of a population was linked to a transformation of the landscape through the clearing of native vegetation and planting of crops.

"Humans can transform an ecosystem much more rapidly and completely than it can be altered by shifting temperature and precipitation patterns," said Lyndon Estes, lead author and associate research scholar at Princeton University's Woodrow Wilson School of International and Public Affairs.

Published in the journal Conservation Biology, the "model provides an initial approach for understanding how agricultural land-use might shift under climate change, and therefore which currently natural areas might be converted to farming," Estes said.

Together with Michael Oppenheimer and Dave Wilcove from the Wilson School's Program in Science, Technology and Policy, as well as researchers from other institutions, Estes studied South Africa - a part of the world considered vulnerable to climate change and whose dominant crops are maize and wheat.

First, the team created a land-use model by estimating an area's potential crop output and simulating the amount of maize and wheat grown between 1979-1999 due to the available historical weather data for these two decades. Ruggedness of each area was also taken into account in order to better measure whether the land would be profitable to farm or not.

Next, the team studied wheat and maize production under 36 climate-response situations, including the effect of rising levels of carbon dioxide and a myriad of future climates. Using their land-use model, the scientists were able to estimate how climate-related changes in productivity would affect the land's utility, and how that would affect the region's land conservation.

The results suggested that the majority of South Africa's conservation lands are likely to stay that way under future climate-change scenarios since most are highly rugged.

"While studying the direct response of species to climatic shifts is important, it's only one piece of a complicated puzzle. A big part of that puzzle relates to how humans will react, and history suggests you don't need much to trigger a change in the way land is used that has a fairly long-lasting impact," Estes said. "We hope that conservation planners can use this approach to start thinking about human climate change adaptation and how it will affect areas needing protection."