For the first time anywhere in the world, tropical rainforest trees in Australia have shifted from absorbing carbon to releasing it, according to a new study published in Nature.
Researchers found that trees in Queensland’s tropical rainforests began emitting more carbon from their trunks and branches than they absorbed about 25 years ago, largely due to rising temperatures and drier conditions. The forests’ root systems, however, remain carbon sinks.
“Tropical forests are usually major carbon sinks, but these ones have flipped,” said lead author Dr. Hannah Carle of Western Sydney University. “Because Australia’s moist tropics are warmer and drier than most, they may show what’s coming for other tropical forests worldwide.”
The finding, based on nearly 50 years of data tracking 11,000 trees across 20 forest sites, marks the first long-term evidence of such a shift. Researchers say it could have serious implications for global climate models and carbon budgets.
“This is the first time a tropical forest has been shown to act as a carbon source for two decades,” said Prof. David Karoly of the University of Melbourne, who was not involved in the study. “If similar changes occur elsewhere, it means climate projections may be underestimating future warming.”
Although the forests still absorb CO₂, their reduced capacity means it will be harder to offset emissions, underscoring the urgency of cutting fossil fuel use.
The study highlights the importance of long-term environmental monitoring. “These unique datasets let us see the real-world effects of climate stress on forests,” said Dr. Raphael Trouvé of the University of Melbourne. “They show that theory doesn’t always match reality—and that our planet’s carbon balance is changing faster than expected.”
