MINNEAPOLIS, Minn. --- Two studies published last week in the journal Science concluded that any major shift to growing biofuel crops for fuel production would actually increase greenhouse gas emissions instead of reduce them.

One study analysis asserted that clearing forests and grasslands to grow the crops would release vast amounts of carbon into the air, more than offsetting the benefits of burning biofuels instead of gasoline.

"We're rushing into biofuels and we need to be very careful," Jason Hill, one of the study co-authors, told the Los Angeles Times. "It's a little frightening to think that something this well intentioned might be very damaging." Hill is an economist and ecologist at the University of Minnesota.

The second study concluded that converting existing farmland from food to biofuel crops would increase greenhouse gas emissions because food production would be shifted to other parts of the world and result in the destruction of more forests and grasslands to make way for farming.

The analysis found that a U.S. cornfield devoted to producing ethanol would have to be farmed for 167 years before it would begin to deliver a net reduction in emissions.

"Any biofuel that uses productive land is going to create more greenhouse gas emissions than it saves," said Timothy Searchinger, the study's lead author. He is a researcher at the Woodrow Wilson School of Public and International Affairs at Princeton University.