(Reuters) - A U.N.-backed forest preservation scheme could become too valuable and complex, raising the risk local communities, the very people seen as key to the scheme's success, could be shut out, scientists say.

Green Business  |  COP15

Reducing emissions from deforestation and degradation, or REDD, has already attracted billion of dollars of funding pledges from rich nations keen to see the scheme established as part of a broader global climate pact from 2013.

REDD would allow developing nations to earn valuable carbon offsets for projects that preserve or rehabilitate forests, which soak up planet-warming carbon dioxide as they grow.

Rich nations would buy the offsets to help them meet emissions reduction goals at home. That demand would underpin forest investments that could reach $30 billion a year by 2020, the United Nations has estimated.