Southern Indiana's rolling hills are greener now than they were a century ago, but the region's rate of reforestation may be on the verge of being outpaced by suburban sprawl's deforestation, according to a new report by Indiana University Bloomington and University of Minnesota researchers in the Proceedings of the National Academy of Sciences.
"Land owners in Indiana today are making different decisions about their land than those who lived here in the 1930s," said IU Bloomington geographer Tom Evans. "But we have seen a flattening out of the reforestation curve, and if things keep going the way they're going, it will eventually be surpassed by deforestation rates tied to suburban growth."
Evans and University of Minnesota geographer Steven Manson apply a modern methodology to land use patterns in Monroe County, Indiana, and southern Yucatan, Mexico. The two researchers argue that some land use models fail to make accurate economic predictions when they overlook diversity in land use preferences at an individual level.
Reforestation of abandoned agricultural areas has been the trend in much of the eastern U.S. since the early 20th century. Evans says the reasons for this are many. Some farm owners found themselves unable to sustain long-term production of areas marginal for crops. The urbanization of America has also played a role, as jobs opportunities in cities allow rural commuters to make a living in cities instead of off their land.
And as jobs and the people who do them have moved into the cities, the cities have grown to accommodate them. Improvements to personal vehicles and infrastructure have resulted in suburban sprawl, which often involves the incorporation and development of farms and pristine areas into residential and commercial zoning projects.
"The movement of people to the suburbs will deeply affect how much deforestation occurs," Evans said. "The current rate of reforestation in rural areas may not counter-balance it in the coming years. A lot of the area in southern Indiana that is least suitable for crops or pasture has now been reforested."
In their PNAS paper, Evans' study of southern Indiana was intended to represent land use in a developed country in contrast to Manson's study of Mexico's Yucatan, which is still developing. Evans and Manson present different but allied methodologies for examining and evaluating land use patterns by land owners. The "agent-based models" the researchers use allow for more analytical power at the individual level.
"Some of the traditional approaches to modeling land use don't work well in really complex environments," Evans said. "The problem is, why people choose to develop or not develop land may may not have much to do with what you might expect just from the financial incentives. We often see people making decisions that are not easily predicted. For example, say your neighbor clear cuts his land for development purposes, and you think it looks terrible. You just might do the opposite of what he did whether or not it's in your economic interests to do so."
Steve Manson looked at whether or not land owners in the Yucatan were maximizing the profits from their land use. Manson found that models that also include land owners who clear just enough land for their household did a better job of predicting past land cover than models with the profit maximizers alone.
Understanding land use patterns is important to geographers, social scientists and economists, but it's also important to governments that find it is in the public interest to regulate land use.
"If you make policy based on assumptions of land owner homogeneity, you're going to miss a lot of the complexity that exists at a local level," Evans said. "Different things drive different people. We don't say it's necessarily possible to predict what our landscapes might look like 10 or 20 years from now. Ultimately what we want to do is give policymakers better insight into what different types of outcomes might happen so they can make planning decisions to cope with those possible outcomes."
Evans' work was funded by grants from the National Science Foundation and NASA.
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