High in Victoria’s Central Highlands stand the mountain ash (Eucalyptus regnans)—the world’s tallest flowering trees, reaching up to 80 m and storing more carbon per hectare than even the Amazon. But decades of research now reveal a troubling pattern: for every 1 °C of warming, these majestic forests lose around 9% of their trees. If global temperatures rise by 3 °C by 2080, nearly a quarter of these forests could vanish. What makes this especially alarming is that mountain ash forests are among Earth’s most carbon-dense ecosystems, locking away between 415–819 tonnes of carbon per hectare, with some untouched stands holding close to 1,500 tonnes. Their decline could flip them from vital carbon sinks into dangerous carbon emitters. The changes are happening quietly but relentlessly. Hotter and drier conditions accelerate “self-thinning,” where giant trees monopolize water and nutrients, pushing smaller trees to their death. As they fall and decay, millions of tonnes of carbon are released—equivalent to putting millions of cars on the road for decades. And the risks don’t stop there: these forests provide critical water supplies to 4.5 million Melburnians and shelter endangered species like Leadbeater’s possum and greater gliders, whose populations are already collapsing. Add in the growing threat of bushfires, and the silent unraveling of these forests becomes one of the clearest warnings yet of how climate change is reshaping our planet’s most powerful ecosystems. More
