🔗 Share this article

Australian tropical rainforest trees have become the first worldwide by transitioning from serving as a CO2 absorber to becoming a source of emissions, due to increasingly extreme temperatures and arid environments.

Critical Change Discovered

This significant change, which affects the trunks and branches of the trees but excludes the root systems, started around a quarter-century back, according to new studies.

Trees naturally store carbon as they develop and release it upon decay and death. Overall, tropical forests are considered carbon sinks – absorbing more CO2 than they release – and this uptake is assumed to increase with higher CO2 levels.

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

Research Findings

Roughly 25 years ago, tree stems and limbs in these forests turned into a carbon source, with increased tree mortality and inadequate regeneration, according to the research.

“This marks the initial rainforest of its kind to show this symptom of change,” commented the principal researcher.

“It is understood that the humid tropical regions in Australia exist in a slightly warmer, drier climate than tropical forests on different landmasses, and therefore it might serve as a coming example for what tropical forests will encounter in global regions.”

Worldwide Consequences

One co-author mentioned that it remains to be seen whether Australia’s tropical forests are a precursor for other tropical forests globally, and additional studies are required.

But if so, the results could have major consequences for international climate projections, CO2 accounting, and climate policies.

“This research is the first time that this critical threshold of a switch from a carbon sink to a carbon source in tropical rainforests has been identified clearly – not merely temporarily, but for 20 years,” stated an authority on climate science.

Worldwide, the portion of carbon dioxide taken in by forests, trees, and plants has been quite stable over the last 20 to 30 years, which was expected to persist under many climate models and strategies.

But should comparable changes – from sink to source – were observed in other rainforests, climate projections may understate heating trends in the coming years. “Which is bad news,” he added.

Continued Function

Although the equilibrium between gains and losses had changed, these forests were still playing an important role in soaking up CO2. But their reduced capacity to absorb extra carbon would make emissions cuts “more challenging”, and require an accelerated transition away from fossil fuels.

Data and Methodology

The analysis utilized a distinct collection of forest data dating back to 1971, including records tracking roughly 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 emphasized the value of gathering and preserving extended datasets.

“We thought the forest would be able to store more carbon because [CO2] is rising. But examining these long term empirical datasets, we find that is incorrect – it allows us to confront the theory with reality and better understand how these systems work.”