Australian tropical rainforests now release more carbon than they absorb, groundbreaking study finds

For decades, we’ve counted on forests as nature’s carbon vacuum cleaners, but alarming new research reveals this fundamental assumption may no longer hold true. A comprehensive study published in Nature has documented the first case of tropical forest woody biomass switching from carbon absorber to carbon emitter—and it’s happening in Australia’s lush Queensland rainforests.

Scientists analyzed nearly 50 years of data from 20 rainforest sites in far northeast Queensland, tracking approximately 11,000 tree stems between 1971 and 2019. Their findings paint a troubling picture: around the year 2000, these moist tropical forests stopped being net carbon sinks and became net carbon sources instead. Before 2000, the forests absorbed about 0.62 metric tons of carbon per hectare annually. Now, they’re releasing 0.93 tons per hectare each year.

The culprit behind this dramatic shift is accelerating tree mortality. Death rates have doubled compared to earlier decades, while new forest growth hasn’t kept pace with these losses. Climate change drives this deadly equation, subjecting rainforest species—evolved for consistently warm, wet conditions—to unprecedented temperature extremes and prolonged droughts that damage plant tissues and inhibit growth.

This research represents a critical wake-up call about climate change’s cascading effects on ecosystems we’ve long relied upon for carbon storage. As these ancient carbon repositories transform into carbon sources, the findings underscore the urgent need for aggressive climate action to protect remaining forest carbon sinks worldwide.