The Amazon rainforest is fast approaching a crucial tipping point. In the wake of relentless deforestation, the rainforest is struggling to recover itself, with huge swathes now turning from a carbon sink into a carbon source.

Environmental scientists in Brazil have found that up to one-fifth of the Amazon rainforest is now emitting more carbon dioxide than it absorbs. Although the rest of the rainforest is still in “working order”, this significant change could hold some profound implications for the world’s climate. 

The full study has not yet been published, but the authors have spoken about their research to BBC Newsnight. The researchers said that their findings were based on new real-world data, gathered by flying aircraft fitted with sensors that can detect concentrations of greenhouse gases. 

One of the chief reasons for this shift is deforestation. Rainforests act as carbon sinks through their wealth of trees and plant life “sucking up” carbon dioxide from the environment and using it for photosynthesis. The carbon is sequestered by the plants and stored as biomass. A huge amount of carbon is also stored in the soil as dead organic matter, such as decomposing trees. 

However, rainforests also emit carbon, primarily through the respiration of microorganisms that decompose trees once they die. Equally, forest fires release the stored carbon back into the atmosphere too. 

In the past, the Amazon has absorbed more carbon than it emits. However, with fewer and fewer trees around thanks to rampant deforestation, parts of the forest are now in carbon debt.

"[The Amazon] used to be, in the 1980s and 90s, a very strong carbon sink, perhaps extracting 2 billion tonnes of carbon dioxide a year from the atmosphere," Professor Carlos Nobre, study co-author from the University of Sao Paulo's Institute for Advanced Studies and Brazil's leading expert on the Amazon, told Newsnight. 

"Today, that strength is reduced perhaps to 1 to 1.2 billion tonnes of carbon dioxide a year."

Another study, released this week in the journal Science Advances, has also looked at the Amazon rainforest's carbon cycle and the disturbance from wildfires. The researchers used models to deduce that increasing temperatures from climate change will double the area burned by wildfires, affecting up to 16 percent of the southern Brazilian Amazon’s forests by 2050. 

All of this will pump out a hell of a lot of carbon – up to 17 billion tonnes (18.7 billion tons) of carbon dioxide – into the atmosphere, enough to change the Amazon from a net carbon sink to a net carbon source.

But it's not all doom and gloom. The researchers found that disaster could be averted by preventing deforestation. If this is achieved, it could reduce the forest fire area by up to 30 percent and cut carbon emissions from fires by 56 percent in the region.

However, judging by Brazil's increasing pace of deforestation in January 2020, the necessary changes likely won't arrive anytime soon.