Impacts of a single fire event on large, old trees in a grass-invaded arid river system

Abstract Background Large old trees are keystone structures of terrestrial ecosystems that provide unique habitat resources for wildlife. Their widespread decline worldwide has serious implications biodiversity and ecosystem integrity. In arid regions, large relatively uncommon often restricted to areas with elevated soil moisture nutrients. Introduced grasses, now pervasive in many dryland environments, also thrive such promoting more frequent intense fire, potentially threatening the persistence trees. Here we report on impact a single wildfire river red gums ( Eucalyptus camaldulensis Dehnh.) riparian woodland invaded by buffel grass Cenchrus ciliaris L.), invader desert worldwide. 2018, 266 > 80 cm equivalent trunk diameter were mapped at six sites ‘pre-fire’ baseline. Within year, impacted large, unprecedented burnt an area 660 km 2 ha 15 days. Sites resurveyed February 2019 assess fate Reference fire severity, calculated from remote-sensed imagery, is provided additional context. Results total, 67 trees, 27% all destroyed. If unburnt patches excluded, 54% exposed destroyed remainder lost average 79% their canopy. Conclusions This severe detrimental effect estimated be centuries old, indicative tree-loss occurring across remote Australia habitats where fuelled predominantly invasive grasses. volumes novel fuels along creeklines combination extreme weather events major factors driving spread, extent impacts causing shift predictable, rainfall-dependent wildfires fires can occur anytime. We predict further abundance similar will widely throughout over next decade substantial long-term multiple species. New strategies urgently required manage better protect critical they provide.