Australian Rainforest Trees Shift from CO2 Absorber to Carbon Emitter in Global Milestone

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

Critical Change Identified

This crucial shift, which affects the trunks and branches of the trees but does not include the underground roots, began approximately 25 years ago, as per recent research.

Forests typically absorb carbon during growth and release it when they decompose. Overall, tropical forests are regarded as carbon sinks – absorbing more CO2 than they release – and this absorption is expected to increase with higher CO2 levels.

However, nearly 50 years of data gathered from tropical forests across Queensland has shown that this vital carbon sink could be under threat.

Research Findings

Approximately 25 years ago, tree stems and limbs in these forests turned into a carbon source, with more trees dying and inadequate regeneration, according to the research.

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

“We know that the humid tropical regions in Australia exist in a somewhat hotter, arid environment than tropical forests on other continents, and therefore it could act as a coming example for what tropical forests will encounter in global regions.”

Global Implications

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

But should that be the case, the results could have major consequences for international climate projections, CO2 accounting, and environmental regulations.

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

On a global scale, the portion of carbon dioxide taken in by forests, trees, and plants has been relatively constant over the last 20 to 30 years, which was expected to persist under numerous projections and strategies.

But should comparable changes – from absorber to emitter – were observed in other rainforests, climate forecasts may underestimate global warming in the coming years. “Which is bad news,” he added.

Continued Function

Even though 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 take in additional CO2 would make emissions cuts “a lot harder”, and require an accelerated shift from carbon-based energy.

Research Approach

This study utilized a unique set of forest data dating back to 1971, including records tracking 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 emphasized the importance of collecting and maintaining long term data.

“We thought the forest would be able to absorb additional CO2 because [CO2] is increasing. But looking at these decades of recorded information, we find that is not the case – it enables researchers to confront the theory with reality and improve comprehension of how these ecosystems work.”