Indigenous lands and protected areas in the Amazon rainforest account for just 10% of all carbon emissions from tropical forests spread across the nine countries of the Amazon in South America, researchers said on Monday. The Amazon, as the world's largest tropical rainforest, is considered key to the fight against climate change because of the vast amounts of planet-warming carbon it stores.

Trees suck carbon dioxide from the air, but when cut down, they release that carbon through burning or rotting. The research, published in the Proceedings of the National Academy of Sciences journal, showed that from 2003 to 2016 the Amazon was a net source of carbon to the atmosphere. The region released about 1,290 million tonnes of carbon when both losses and gains were combined.

While previous research has largely focused on carbon emissions linked to deforestation, the new study also took into account those caused by natural factors like drought, as well as gains made through forest growth. Using data from satellite imagery and field visits, the study showed tree growth helped indigenous lands - which cover about a third of the Amazon - record the lowest net carbon loss.

The bulk - 90% - of net emissions were found to come from outside indigenous and protected areas. "What we find is that from a carbon standpoint, protected land and indigenous territories are doing a tremendous job in buffering against losses, particularly losses associated with deforestation," said Wayne Walker, a scientist at the Woods Hole Research Center, a US climate science institute.

But those protected lands are not immune from losses, added Walker, the study's lead author. "Losses are seen from degradation associated with illegal activities, illegal mining and illegal deforestation ... to natural-related disturbance losses associated with drought and forest fires," he told the Thomson Reuters Foundation.

The study used and updated data first published in the journal Science in 2017, he noted. With rising deforestation rates, particularly in Brazil - home to the biggest share of the Amazon - protecting the rainforest is an urgent priority, including doing more to safeguard indigenous lands and tenure, scientists say. In Brazil, those lands are increasingly under threat, as right-wing President Jair Bolsonaro has said indigenous reserves are too large and his government wants to allow commercial mining and agriculture there.

Walker said the study showed that compared with unprotected land, forests under the stewardship of indigenous peoples and local communities continued to have better carbon outcomes. "Their role is critical and must be strengthened if Amazon basin countries are to succeed in maintaining this globally important resource," he added.