Indigenous territories and protected natural areas across nine South American countries account for more than half the carbon stored in the Amazon, the study published in the journal Carbon Management reported.
If this land is exploited for logging, mining or commercial farming, much of the carbon will be released into the atmosphere, accelerating global warming, the study "Forest Carbon in Amazonia: The Unrecognized Contributions of Indigenous Territories and Protected Natural Areas" said.
"International recognition and investment in indigenous and protected areas are essential to ensuring their continued contribution to global climate stability," Richard Chase Smith, of Peruvian NGO Common Good Institute, said in a statement.
Territories of Amazonian indigenous people store more forest carbon than whole tropical countries including Indonesia and the Democratic Republic of Congo, Wayne Walker, a scientist who worked on the study, said in a statement.
Interest in the Amazon's resources from ranchers, mining companies and timber barons could force indigenous people off the land and contribute to deforestation, thus releasing more carbon into the atmosphere.
More than 1.3 million square kilometres of Amazonian protected areas, an area larger than the Colombian, Ecuadorean and Peruvian Amazon combined, are at risk, the study said.
"We have never been under so much pressure," Edwin Vásquez, president of the Indigenous Coordinating Body of the Amazon Basin, a rights group, said in a statement.
The Amazon embraces 2,344 indigenous territories and 610 protected areas. Preserving these territories would cost $2-4 billion, the study's authors said, arguing that present funding commitments for reducing deforestation could cover the expense.
Destruction of carbon-rich ecosystems in the Amazon would diminish their ability to function properly, causing potentially irreversible damage to the atmosphere, the study said.
This story was originally published on Thomson Reuters Foundation. (Reporting By Chris Arsenault; Editing by Tim Pearce)