Losing grasslands in the Corn Belt

Mar 1, 2013

—Commodity boom blamed for loss of grasslands, birds.

Production agriculture’s reach for higher profits in response to the recent commodity boom is to blame for a depletion of grasslands in the western Corn Belt and diminishing populations of native birds in North America and Europe, according to two studies released in last week.

The studies come at a time when the future of conservation programs and biofuels could depend on the outcome of ongoing budget battles in Washington and on a national campaign by oil companies and others to eliminate the Renewable Fuel Standard.

A South Dakota State University (SDSU) study sounds alarm bells about the potential future of advanced biofuels production using perennial bioenergy crops such as prairie grasses. It points to the loss of grasslands in six states as reason for concern that many western Corn Belt states may be seeing an advanced biofuels opportunity slip away.

The study, “Recent Land Use Change in the Western Corn Belt (WBC) Threatens Grasslands and Wetlands,” said the expansion of corn and soybean acres into grasslands in North Dakota, South Dakota, Iowa, Nebraska and Minnesota in response to doubling commodity prices and feedstock demand for biofuels has led to the loss of some 1.3 million acres of grasslands in those states between 2006 and 2011.

“Across the WCB, we found a net decline in grass-dominated land cover totaling nearly 530,000 ha [about 1.3 million acres],” the study said.

“With respect to agronomic attributes of lands undergoing grassland conversion, corn/soy production is expanding onto marginal lands characterized by high erosion risk and vulnerability to drought.

“Longer-term land cover trends from North Dakota and Iowa indicate that recent grassland conversion represents a persistent shift in land use rather than short-term variability in crop rotation patterns.

“Our results show that the WCB is rapidly moving down a pathway of increased corn and soybean cultivation. As a result, the window of opportunity for realizing the benefits of a biofuel industry based on perennial bioenergy crops, rather than corn ethanol and soy biodiesel, may be closing in the WCB.”

The SDSU study does not address overall loss of agriculture land in the U.S. in the past several decades.

U.S. agriculture land as a whole has been diminishing at the hands of development since the early 1980s, according to the Farmland Information Center (FIC).

Between 1982 and 2007, a total of 22.3 million acres of farmland was converted to developed land in the U.S. That includes a total of about 1.1 million acres of farmland in Iowa, North Dakota, South Dakota, Minnesota and Nebraska, the study found, according to the FIC.

Bird losses

A second study, entitled “Pesticide Acute Toxicity Is a Better Correlate of U.S. Grassland Bird Declines than Agricultural Intensification,” points to the use of pesticides as the reason for a decreasing population of so-called “agricultural” birds across North America and Europe.

The study conducted by the Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, the Pest Management Regulatory Agency and Health Canada, found the use of pesticides and herbicides are at least partly to blame for a decline in “common agricultural birds” in North America and in Europe.

On a state-by-state basis, researchers looked at a number of variables to predict the number of grassland species increasing or declining, according to breeding bird surveys conducted between 1980 and 2003.

“Best predictors of species declines were the lethal risk from insecticide use modeled from pesticide impact studies, followed by the loss of cropped pasture,” the study said.

“Loss of permanent pasture or simple measures of agricultural intensification such as the proportion of land under crop or the proportion of farmland treated with herbicides did not explain bird declines as well.

“Because the proportion of farmland treated with insecticides and more particularly the lethal risk to birds from the use of current insecticides, feature so prominently in the best models, this suggests that, in the U.S. at least, pesticide toxicity to birds should be considered as an important factor in grassland bird declines.”

In Corn Belt states, the study identified 61 declining bird species, including 31 that are considered to be on a “significant” decline.

“Our results suggest that the use of lethally toxic insecticides cannot be ignored when trying to identify causes of grassland population declines in North America,” the study said.

“Indeed, they offer a more plausible explanation for overall declines than does the oft-cited habitat loss through agricultural intensification. It was remarkable that loss of permanent pasture did not appear to be much of a predictor of grassland bird declines.” — Todd Neeley, DTN