As the debate over global warming and the idea of “going green” becomes more popular, many environmentalists and politicians have viewed biofuel as a logical replacement for fossil fuels.

But according ABC News, two recently released studies are questioning the global movement toward biofuel, claiming production of biofuel actually contributes to global warming, doing more harm than good.

The studies, one conducted by Minnesota-based Nature Conservancy and one by Princeton University, examined growing vegetation used for biofuel and the environmental impact it has on global warming.

The researchers said U.S. demand for ethanol crops like corn, soy and switchgrass has resulted in the conversion across the globe of natural habitats, like grasslands and rainforests, into fuel-ready farmland, which has released mass amounts of carbon into the air, ABC News reported.

“You ask the world’s farmers to produce energy and that’s going to take additional land and that land has to come from somewhere,” Joe Fargione, regional science director for the Natural Conservancy and the lead author of one study, told ABCNews.com.  “Unfortunately, much of it is coming from our natural ecosystem. What’s the consequence of that?”

“Any biofuel that causes the clearing of natural ecosystems will increase global warming,” he continued.

Fargione also argues that the findings call into question the energy bill recently passed by Congress, which calls for increased biofuel production 15 billion gallons by 2015.

“If you create a carbon tax or a low carbon fuel standard that penalizes fuel based on the amount of carbon it emits and then you miscalculate how much carbon biofuels are actually emitting, then biofuels are actually worse than the fossil fuels they replace,” he told ABCNews.com.

But according to the Renewable Fuels Association, a trade organization representing the U.S. ethanol industry, the studies failed to put biofuel production in context with fossil fuel production.

Don’t give up completely on biofuels just yet, ABC says. Both sets of researchers say there is still hope in biofuel made from abandoned, depleted farmland and biomass waste, like unused parts of a corn plant.

Still, Fargione maintains that biofuels aren’t the only answer in the fight against global warming. “It’s worth doing, but it’s not a silver bullet,” he said.