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Trees in Australia's tropical rainforests have become the first worldwide by transitioning from serving as a CO2 absorber to turning into a carbon emitter, driven by increasingly extreme temperatures and arid environments.

Critical Change Discovered

This crucial shift, which affects the stems and limbs of the trees but does not include the underground roots, began approximately 25 years ago, as per new studies.

Trees naturally store carbon during growth and release it upon decay and death. Overall, tropical forests are regarded as carbon sinks – taking in more carbon dioxide than they release – and this absorption is assumed to increase with rising atmospheric concentrations.

However, close to five decades of data gathered from tropical forests across Queensland has shown that this essential carbon sink may be at risk.

Research Findings

Roughly 25 years ago, tree stems and limbs in these forests became a net emitter, with increased tree mortality and inadequate regeneration, as the study indicates.

“It’s the first tropical forest of its kind to show this symptom of transformation,” stated the principal researcher.

“It is understood that the moist tropics in Australia occupy a somewhat hotter, arid environment than tropical forests on different landmasses, and therefore it might serve as a future analog for what tropical forests will encounter in other parts of the world.”

Worldwide Consequences

A study contributor mentioned that it is yet unclear whether Australia’s tropical forests are a precursor for other tropical forests globally, and additional studies are needed.

But should that be the case, the findings could have major consequences for global climate models, CO2 accounting, and climate policies.

“This research is the initial instance that this critical threshold of a switch from a carbon sink to a carbon source in tropical rainforests has been definitively spotted – not just for one year, but for 20 years,” stated an authority on climate science.

On a global scale, the share of carbon dioxide absorbed by forests, trees, and plants has been quite stable over the last 20 to 30 years, which was expected to persist under numerous projections and policies.

But should comparable changes – from absorber to emitter – were detected in other rainforests, climate projections may understate heating trends in the coming years. “Which is bad news,” it was noted.

Ongoing Role

Even though the equilibrium between growth and decline had changed, these forests were still playing an important role in soaking up CO2. But their reduced capacity to take in additional CO2 would make emissions cuts “a lot harder”, and require an even more rapid shift from carbon-based energy.

Data and Methodology

The analysis utilized a distinct collection of forest data dating back to 1971, including records tracking approximately 11,000 trees across numerous woodland areas. It focused on the carbon stored in trunks and branches, but excluded the changes in soil and roots.

Another researcher highlighted the importance of gathering and preserving extended datasets.

“It was believed the forest would be able to store more carbon because [CO2] is rising. But looking at these decades of recorded information, we discover that is incorrect – it enables researchers to confront the theory with reality and improve comprehension of how these systems work.”