🔗 Share this article Australian Rainforest Trees Shift from Carbon Sink to Emissions Source in Global Milestone Trees in Australia's tropical rainforests have achieved a global first by shifting from acting as a carbon sink to becoming a source of emissions, due to increasingly extreme temperatures and drier conditions. The Tipping Point Discovered This crucial shift, which affects the trunks and branches of the trees but does not include the root systems, began approximately 25 years ago, as per recent research. Trees naturally store carbon during growth and emit it upon decay and death. Generally, tropical forests are considered carbon sinks – taking in more carbon dioxide than they release – and this uptake is expected to increase with higher CO2 levels. However, nearly 50 years of data collected from tropical forests across northern Australia has shown that this essential carbon sink may be at risk. Research Findings Roughly 25 years ago, tree trunks and branches in these forests became a net emitter, with more trees dying and insufficient new growth, as the study indicates. “This marks the initial rainforest of its kind to show this symptom of change,” commented the principal researcher. “It is understood that the moist tropics in Australia exist in a slightly warmer, drier climate than tropical forests on different landmasses, and therefore it could act as a future analog 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 precursor for other tropical forests globally, and further research are required. But should that be the case, the findings could have significant implications for global climate models, carbon budgets, and environmental regulations. “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 definitively spotted – not merely temporarily, but for two decades,” 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 past few decades, which was assumed to continue under many climate models and strategies. But should comparable changes – from absorber to emitter – were observed in other rainforests, climate projections may underestimate global warming in the coming years. “This is concerning,” it was noted. Ongoing Role 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 even more rapid transition away from fossil fuels. Research Approach The analysis utilized a unique set of forest data starting from 1971, including records tracking approximately 11,000 trees across 20 forest sites. It considered the carbon stored in trunks and branches, but excluded the gains and losses below ground. An additional expert highlighted the importance of gathering and preserving extended datasets. “It was believed 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 incorrect – it allows us to compare models with actual data and better understand how these systems work.”