One analysis suggests that clearing forests and grasslands to grow biofuel crops releases vast amounts of carbon into the air, far more than the carbon spared from the atmosphere by burning biofuels instead of gasoline.
'We're rushing into biofuels, and we need to be very careful. It's a little frightening to think that something this well intentioned might be very damaging,' the Environmental News Network quoted Jason Hill, an economist and ecologist at the University of Minnesota, as saying.
The second analysis suggests that even converting existing farmland from food to biofuel crops increases greenhouse gas emissions.
When food production is shifted to other parts of the world, it results in the destruction of more forests and grasslands to make way for farmland, says the study.
The analysts reckoned that that it would take about 167 years of farming for a US cornfield devoted to producing ethanol to begin achieving 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, a researcher at the Woodrow Wilson School of Public and International Affairs at Princeton University and the study's lead author.
Intrigued by the studies' findings, 10 prominent ecologists and environmental biologists have written to US President George W. Bush and congressional leaders, calling for a new policy 'that ensures biofuels are not produced on productive forests, grassland or cropland.'