Nature study: colonial era left Australia's forests more prone to megafires

A team led by palaeoecologist Michael-Shawn Fletcher of the University of Melbourne has reconstructed 1,000 years of fire and vegetation history in a eucalypt forest in south-eastern Australia, in a paper in Nature (online since 7 October 2026). It is based on a sediment core from a lake in Croajingolong National Park, on the traditional lands of the Gunaikurnai people, whose land council organisation is among the co-authors. Pollen and charcoal were dated using lead-210 and radiocarbon data. These are measured data from a natural archive, not a model calculation.

For 800 years, the data indicate, the landscape was an open, grassy woodland kept open by small, regular cultural burns. After British colonisation, which the authors date from 1788, eucalypt cover rose fourfold according to the study (the Nature news report speaks of a doubling around 1840), woody shrubs spread, and from the mid-19th century the share of charcoal from very hot fires increased. The freely available summary gives no precise uncertainty range for the dating. Importantly, the authors say the changes began before human-caused warming became noticeable.

The researchers describe a self-reinforcing "catastrophic wildfire loop": hotter fires favour more flammable vegetation, which in turn feeds hotter fires. Fletcher told Nature the study offers "another variable" for tackling the problem, rather than focusing only on climate change. According to Nature, the 2019/20 "Black Summer" fires burned more than eight million hectares of forest in south-eastern Australia. The authors consider it essential to integrate Indigenous knowledge into fire management; that this would lower the risk of devastating fires – especially as the climate warms – is their conclusion, which the study itself did not test.