LAND use change is something of a controversial subject, and its study is often used as a tool for discouraging further agricultural development in or near sensitive ecosystems.
A 2013 study published this month in the journal Proceedings of the National Academies suggests that economic incentives have led to increased corn and soybean plantings in the western Corn Belt (WCB), to the detriment of native grasslands and the endangered Prairie Pothole Region.
The study -- conducted by South Dakota State University ecologists Christopher Wright and Michael Wimberly with the university's Geographic Information Science Center of Excellence -- looked at the rate and type of land conversion in the Dakotas, Nebraska, Minnesota and Iowa from 2006 through the 2011 growing season. The study found that more than 1.3 million acres of grass-dominated land cover in the WCB were converted to cropland.
The researchers categorized much of the converted land as "marginal," presenting a high risk for erosion and vulnerability to drought.
A doubling of commodity prices in recent years, coupled by other economic incentives and federal policies, have led farmers in the WCB to plant more corn and soybeans despite some meteorological risk.
"The western periphery of the Corn Belt is characterized by a climate where mean annual evapotranspiration exceeds mean annual precipitation, suggesting that farmers here are willing to accept higher levels of drought risk in seeking higher cash returns from corn and soybeans," the researchers explained. "Federal crop insurance and disaster relief programs mitigated this risk, creating incentives for converting grassland to cropland, potentially at cross purposes with other national policies intended to conserve grassland."
Grassland conversion between 2006 and 2011 was primarily concentrated in North and South Dakota, east of the Missouri River (Map). In these states alone, the researchers found a net loss of 671,000 acres of grassland. Iowa, meanwhile, saw a net loss of 376,000 acres of grassland during the same period.
Comparing the rate of grassland conversion to the rate of deforestation seen in Brazil, Malaysia and Indonesia in the 1980s and 1990s, the report notes an annual conversion rate of 1.0-5.4%. Historically, U.S. grassland conversion rates have not reached such levels since the rapid spread of agricultural mechanization in the 1920s and 1930s.