環境：オーストラリアの植民地化が山火事の激化に寄与した可能性

Changes to land management following British colonization of Australia may have amplified the influence of climate change on increasing wildfire intensity, research in Nature indicates. The study reveals 1,000 years of vegetation, fire and landscape change in southeastern Australia, showing how the colonizers shaped the fire-prone eucalypt forests that cover the area today. Reinstating Indigenous cultural burning practices might help to reduce wildfire risk.

Climate change is widely recognised as a main driver of global wildfires, but land management may be an unaccounted-for driving force. Before British colonization, the Indigenous Gunaikurnai people of southeastern Australia used small-scale cultural burning to reduce fuel build-up and prevent large wildfires. This practice was discontinued following British colonization in the 19th century, and there is limited evidence for how vegetation and fire dynamics differed before and after these changes in land management. Some widely used national datasets further obscure these changes by presenting post-colonial forest as the 'natural' reference point.

To investigate southeast Australia’s long-standing vegetation and fire history, Michael-Shawn Fletcher and colleagues extracted and analysed a 1-m sediment core from the deepest part of Purghagoolah (Lake Elusive) in southeastern Australia. By analysing ancient pollen, charcoal and sediment layers, they reconstructed 1,000 years of vegetation, fire activity and landscape change. The authors find that under Gunaikurnai management, the area existed as open woodland that remained stable for over 800 years. Following changes in land management after colonization and the halting of cultural burning in the 1800s, eucalypt tree cover increased fourfold from around 9% to 34%. Macroscopic charcoal analysis shows that the intensity, temperature and frequency of the fires increased under post-colonization land management, owing to fuel accumulation (eucalypt trees are highly flammable). Rates of soil erosion also increased after colonization. The changes predated the emergence of human-driven climate warming in around the 1950s, suggesting that historical land-use change might have made a long-term contribution to rising wildfire occurrences.

Highly flammable eucalypt forests cover much of southeast Australia today. The 2019–2020 Black Summer fires, which burned more than 24 million hectares, serve as a recent example of the scale and long-lasting impact of fires in these forests. The authors conclude that Indigenous knowledge and cultural burning practices could help to inform future wildfire management strategies.

• Article
• Published: 07 October 2026

Fletcher, MS., Romano, A., O’Shea, C. et al. Australia’s current wildfire crisis linked to colonial land-use change. Nature (2026). https://doi.org/10.1038/s41586-026-11097-z