🔗 Share this article

Australian tropical rainforest trees have achieved a global first by transitioning from serving as a CO2 absorber to turning into a carbon emitter, due to rising heat extremes and drier conditions.

Critical Change Discovered

This crucial shift, which affects the trunks and branches of the trees but excludes the underground roots, began approximately a quarter-century back, as per recent research.

Forests typically absorb carbon as they develop and release it when they decompose. Overall, tropical forests are considered carbon sinks – absorbing more CO2 than they emit – and this absorption 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 vital 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 more trees dying and insufficient new growth, according to the research.

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

“It is understood that the humid tropical regions 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 experience 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 worldwide, and additional studies are required.

But should that be the case, the results could have significant implications for global climate models, CO2 accounting, and climate policies.

“This paper is the first time that this tipping point of a transition from a carbon sink to a carbon source in tropical rainforests has been identified clearly – not merely temporarily, but for two decades,” stated an authority on climate science.

Worldwide, the share of carbon dioxide taken in by forests, trees, and plants has been quite stable over the past few decades, which was expected to persist under numerous projections and strategies.

But if similar shifts – from sink to source – were observed in other rainforests, climate projections may underestimate global warming in the future. “This is concerning,” he added.

Continued Function

Although the equilibrium between growth and decline had shifted, these forests were still playing an important role in soaking up CO2. But their diminished ability to absorb extra carbon would make emissions cuts “more challenging”, and require an even more rapid transition away from fossil fuels.

Research Approach

The analysis utilized a distinct collection of forest data dating back to 1971, including records monitoring roughly 11,000 trees across numerous woodland areas. It considered the carbon stored above ground, but not the changes in soil and roots.

An additional expert highlighted the importance of gathering and preserving extended datasets.

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