Indigenous population expansion and cultural burning reduced shrub cover that fuels megafires in Australia

Indigenous burning practices in Australia once halved shrub cover, reducing available fuels and limiting wildfire intensity for thousands of years, but the removal of these practices following European colonization has led to an increase in the tinder that has fueled today’s catastrophic megafires, researchers report. The findings suggest that reintroducing cultural burning practices could provide a strategy to curb future fires. “Through detailed histories of Indigenous burning regimes across the world and Indigenous-led collaborations in contemporary wildfire management projects, we can inform sustainable and healthy solutions that ‘tame the flames’ threatening global socioenvironmental systems,” write the authors. Climate change is increasing the frequency and intensity of wildfires in many regions, particularly the forests of western North America and southeastern Australia. In addition to anthropogenic climate change, human forest management and fire suppression have led to a buildup of shrubby vegetation that fuels more intense fires. This dense shrub layer allows ground fires to spread to the forest canopy above, resulting in destructive and difficult-to-control crown fires. For millennia, humans have used fire as a tool, with Indigenous groups worldwide practicing “cultural burning” to promote biodiversity, improve hunting, and reduce fuel loads through frequent, low-intensity burns. This approach creates spatial diversity in vegetation and helps to prevent severe wildfires. In fire-prone regions like southeastern Australia, colonial suppression of Indigenous burning practices has caused fuel loads to increase, resulting in more frequent high-intensity fires. However, while traditional Indigenous burning practices in Australia have recognized benefits, data on vegetation structure under Indigenous management is limited. To address this gap, Michela Mariani and colleagues analyzed 2833 archaeological and palaeoecological records of vegetation cover, climate, fire activity, and human population size, spanning from the pre-human landscapes of the Last Interglacial to the post-colonial period. Mariani et al. found that Indigenous population expansion and cultural burning practices during the mid-late Holocene (6,000 to 1,000 years ago) coincided with a roughly 50% reduction in shrub cover (from ~30% from the early to mid-Holocene to 15% during the late to mid-Holocene). However, since British colonization in the 18^th century, shrub cover has surged to an unprecedented 35% - surpassing levels seen even before human presence on the continent – contributing to modern megafires.