U.S. experts warn that rules governing biofuel production encourage deforestation and mean the technology is therefore a "false" method of reducing greenhouse gas emissions.

In a study to published on Oct. 23 in the journal Science, a group of 13 scientists called for the rules, which contain a loophole exempting carbon dioxide emitted by bioenergy regardless of its source, to be overturned.

"The error is serious, but readily fixable," said lead researcher Timothy Searchinger of Princeton University.

The study called for the issue to be addressed in the climate treaty that nations around the world are hoping to sign at the Copenhagen summit in December to supercede the Kyoto Treaty.

Researchers said numerous analyses -- including one released by the U.S. Department of Energy -- have found that this loophole "could lead to the loss of most of the world's natural forests as carbon caps tighten."

The rules were found in the Kyoto Protocol, which was framed in 1997 and put into force in 2005, legally binding 37 industrialized countries to cut their greenhouse gas output, noted researcher Daniel Kammen.

The European Union's Emissions Trading System and this year's climate bill passed by U.S. House members also enable the same loophole, said Kammen, from the University of California in Berkeley.

The study said it meant that "bioenergy from any source, even that generated by clearing the world's forests, a potentially cheap, yet false, way to reduce greenhouse gas emissions."

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