Biodiversity impacts of the 2019–2020 Australian megafires

With large wildfires becoming more frequent, we must rapidly learn how megafires impact biodiversity to prioritize mitigation and improve policy. A key challenge is to discover how interactions among fire-regime components, drought and land tenure shape wildfire impacts. The globally unprecedented 2019-2020 Australian megafires burnt more than 10 million hectares, prompting major investment in biodiversity monitoring. Collated data include responses of more than 2,000 taxa, providing an unparalleled opportunity to quantify how megafires affect biodiversity. We reveal that the largest effects on plants and animals were in areas with frequent or recent past fires and within extensively burnt areas. Areas burnt at high severity, outside protected areas or under extreme drought also had larger effects. The effects included declines and increases after fire, with the largest responses in rainforests and by mammals. Our results implicate species interactions, dispersal and extent of in situ survival as mechanisms underlying fire responses. Building wildfire resilience into these ecosystems depends on reducing fire recurrence, including with rapid wildfire suppression in areas frequently burnt. Defending wet ecosystems, expanding protected areas and considering localized drought could also contribute. While these countermeasures can help mitigate the impacts of more frequent megafires, reversing anthropogenic climate change remains the urgent broad-scale solution.

Key future takeaways are as follows:

• The most important aspect to consider is the influence of fire frequency and interval on the vulnerability of species to future wildfires.
• While fire management agencies already prepare for high-risk fire seasons during drought, localized climatic conditions are another aspect for managers to consider.
• Expanding and managing the protected area estate could help to buffer species from the effects of changing fire regimes.
• Indigenous fire practices that place the right fire regimes into the right country, are therefore increasingly important for improving fire management for biodiversity conservation.