Australia’s tropical rainforests have recently been identified as the first in the world to emit more carbon than they absorb, according to a groundbreaking study published in the journal *Nature*. This alarming trend, attributed to the effects of climate change, raises serious concerns for global emissions reduction goals that rely on the natural carbon-sequestering capabilities of ecosystems.
A Shift in Carbon Dynamics
Historically, rainforests have been viewed as vital carbon sinks, effectively absorbing more carbon dioxide than they release. However, research focusing on Queensland’s forests reveals that extreme weather conditions have resulted in a higher incidence of tree mortality than new growth. Dr. Hannah Carle, the lead author of the study from Western Sydney University, emphasised the implications of these findings, stating, “Current models may overestimate the capacity of tropical forests to help offset fossil fuel emissions.”
The study indicates that the conversion of woody biomass—comprising the trunks and branches of deceased trees—into carbon emitters began roughly 25 years ago. This shift poses a significant threat to the forests’ role in mitigating climate change, as Dr. Carle warns, “Forests help to curb the worst effects of climate change by absorbing carbon dioxide released from burning fossil fuels, but our work shows this is under threat.”
Climate Change Accelerating Tree Deaths
The research draws upon nearly five decades of data from 20 forests across Queensland, revealing a troubling correlation between climate change and increased tree mortality. Factors such as rising temperatures, prolonged droughts, and heightened atmospheric dryness have collectively contributed to the decline in tree health and growth. Furthermore, the study indicates that the frequency and intensity of cyclones have risen, further exacerbating the challenges for these vital ecosystems.
Dr. Carle noted, “We have in this study evidence that Australia’s moist tropical forests are the first of their kind globally to exhibit this [woody biomass] change,” labelling the findings as potentially indicative of a larger, concerning trend among tropical forests worldwide.
Global Implications for Emissions Reduction
The senior author of the study, Patrick Meir, echoed Dr. Carle’s concerns, describing the results as “very concerning” and suggesting that similar shifts may occur in tropical forests globally. While he acknowledged the need for further research to fully comprehend the implications, the findings underscore the precarious balance that existing carbon models rely upon.
Australia, known for its significant per capita greenhouse gas emissions, has recently announced ambitious carbon reduction targets, aiming for a minimum 62% reduction from 2005 levels within the next decade. However, the country faces ongoing scrutiny regarding its reliance on fossil fuels, exemplified by the recent decision to extend operations of the North West Shelf gas project for an additional 40 years.
The Current Climate Crisis
A recent report highlighted that Australia has already exceeded a temperature increase of 1.5°C, with no community spared from the “cascading, compounding, and concurrent” risks posed by climate change. This stark reality elevates the urgency of addressing the issues presented by the study of Queensland’s rainforests.
Why it Matters
The findings regarding Australia’s rainforests serve as a critical warning for global climate policy and conservation efforts. If these ecosystems, once regarded as resilient buffers against climate change, are becoming net carbon emitters, it could undermine international emissions reduction commitments and exacerbate the climate crisis. As the world grapples with rising temperatures and increasing environmental instability, the health of Australia’s rainforests has far-reaching implications, signalling urgent action is required to protect not only these vital ecosystems but the planet as a whole.
