Rivers up in smoke: impacts of Australia's 2019-2020 megatires on riparian systems

Background. Increasing occurrence of megafires and wildfires is threatening the integrity of many natural systems and sustainability of the ecosystem services they provide. For example, the 2019-2020 Australian fires were one of the costliest natural disasters in the country's recorded history. Aims. This study aims to analyse the extent and severity of the fires on riparian systems across coastal catchments of New South Wales. We open a discussion about whether megafires and wildfires are creating novel riparian ecosystems and if prescribed and cultural burns should be used as a riparian vegetation management technique. Key results. Of the 81 304 km of stream analysed, similar to 29% (23 266 km) were impacted by extreme or high-severity burning, with vegetation canopy completely consumed, or completely scorched and partially consumed. A further 21% (17 138 km) experienced moderate to low-severity burning, with partial canopy scorching or understorey burning. Such widespread, synchronous burning of riparian systems is unprecedented. Conclusion and implications. Riparian management strategies must evolve to mitigate against future catastrophic fires that are becoming more frequent and severe under climate change. Research needs to establish the extent to which Australian riparian ecosystems are adapted to fire, the regimes and customs of cultural burning in these zones, and how to use such burning in riparian management.