Growing palm oil trees to make biofuels could be accelerating the effects of climate change, new research showed, adding further weight to claims the crop is not environmentally sustainable.

In a paper published in the journal Nature, an international team of scientists examined how the deforestation of peat swamps in Malaysia to make way for palm oil trees is releasing carbon which has been locked away for thousands of years.

Microbes then penetrate the carbon and the harmful greenhouse gas carbon dioxide is released, which is thought to be the biggest contributor to global warming.

Unsustainable methods of growing crop-based biofuels have come under fire as environmentalists question the emissions savings they make, the agricultural land they occupy and whether the growth of certain crops contribute to deforestation.

More than 80 percent of palm oil is grown in Indonesia and Malaysia. According to some estimates, an area the size of Greece is cleared every year for palm oil plantations.