Forests soak up vast amounts of planet-warming carbon dioxide each year and are crucial in the fight to curb climate change.

Many governments and scientists want to put a price on the carbon locked away in forests as an incentive to curb deforestation, which contributes nearly a fifth of mankind's greenhouse gas emissions.

Researchers led by Oscar Venter of the University of Queensland in Australia studied data from 808 concessions in Kalimantan, Indonesia's part of Borneo island, covering 8 million hectares (20 million acres).

Of this area, they found 3.3 million hectares of forest within the concessions remained uncleared and was under imminent threat of being converted to oil palm plantations.

'They are not meant to be clearing forest for palm oil development. It's pretty clear that forests are being felled for oil palm,' said Mr Venter, a conservation biologist and lead author of the study published on Friday in Conservation Letters.

Mr Venter, speaking to Reuters from Brisbane in Queensland state, said the team conducted an economic analysis by asking how much it would cost the concession owners to stop clearing the forest and how to pay for lost revenues.

They looked at the role of carbon credits under a UN-backed scheme that aims to reward developing nations for preserving forests in return for tradeable carbon offsets.

The scheme, called reduced emissions from deforestation and degradation, or REDD, is likely to be included in a broader UN climate pact to be negotiated in December.

A new climate pact from 2013 could usher in a multi-billion dollar trading scheme for REDD credits that rich nations could buy to help meet emissions reduction targets. -- REUTERS