Australian rainforests no longer serve as a carbon sink: study

Australia’s tropical rainforests, once crucial carbon sinks, have started emitting more carbon dioxide (CO₂) than they absorb, according to a new scientific study published Thursday. Researchers attribute this concerning change to climate change, warning that rising temperatures and drought are disturbing the fragile balance that has historically allowed rainforests to store carbon and help regulate the global climate.

A turning point in forest carbon dynamics

The research team examined nearly 50 years of growth data from Queensland’s tropical rainforests, discovering that around the year 2000, these ecosystems started releasing more CO₂—mainly through the decay of dead trees—than they could absorb via photosynthesis.

“Extreme heat and moisture stress caused by climate change have led to higher tree mortality rates,” explained Professor Patrick Meir, senior author of the study. “This is the first time we’ve observed such a persistent pattern in a natural, undisturbed forest—and it’s very concerning.”

Climate extremes and cyclones intensify the trend

The findings, published in the journal Nature, identify temperature spikes, atmospheric dryness, and drought as the main drivers of forest decline. Additionally, **Cyclones—expected to intensify further due to climate change—**have contributed to the damage.

David Bauman, co-author and scientist at the French National Research Institute for Sustainable Development, said the results mirror earlier trends in the Amazon rainforest, where rising tree deaths are weakening the region’s carbon storage capacity. “The timing was earlier than we expected, and the climatic effects were stronger,” he noted. 

A warning for the world’s rainforests

Experts say the implications of this research go beyond Australia. “All tropical forests are likely to respond similarly,” said Meir, although the exact timing may vary by region.

Dr Melanie Zeppel, Associate Director at Pollination, a climate investment firm, called the results “a wake-up call,” emphasising that “the impacts of climate change on forest carbon are more severe than previously reported.”

Global climate targets under threat

While the researchers acknowledged remaining uncertainties—particularly concerning roots and soil carbon dynamics, they emphasised that the evidence indicates an accelerating climate crisis. “Limiting global warming to below 1.5°C has become more urgent and more difficult,” said Bauman.

Despite its vulnerability to climate-related disasters, Australia remains one of the world’s largest exporters of coal and gas, with per capita CO₂ emissions among the highest globally, according to World Bank data.

The United Nations recently reported that the yearly rise in global atmospheric CO₂ was the highest ever recorded, highlighting the urgent need for stronger international measures to reduce emissions.