Smoke on the water: Pervasive effects of megafires on the mammal fauna of the world's largest wetland

Abstract Disruptions in fire regimes increasingly threaten biodiversity worldwide, yet the long‐term impacts of megafires on mammal assemblages in fire‐prone ecosystems remain poorly understood. The 2020 megafires in the Brazilian Pantanal, the world's largest tropical wetland, burned one‐third of its area, causing unprecedented biodiversity impacts and highlighting the need to understand ecological consequences. We assessed the effects of the 2020 megafires on mammal diversity and relative abundance in the Pantanal Matogrossense National Park using environmental DNA (eDNA) metabarcoding, camera trapping and Bayesian multispecies occupancy models. These methods allowed us to evaluate species, site and assemblage‐level responses to fire, accounting for imperfect detection and landscape heterogeneity. Despite the Pantanal being fire‐prone, we observed significant negative effects on mammals at multiple ecological levels, persisting 2 years post‐fire. Species richness declined from 84 species observed pre‐fire to 44 observed post‐fire. eDNA metabarcoding identified 38 species (23 exclusively), while camera traps recorded 21 species (6 exclusively). A significant negative correlation was found between burned area proportion and both species richness and aggregated relative abundance per site. Impacts were severe on large‐bodied, threatened species, such as the giant armadillo ( Priodontes maximus ), jaguar ( Panthera onca ) and lowland tapir ( Tapirus terrestris ). They experienced significant declines in relative abundance, highlighting the vulnerability of megafauna to severe wildfires. The combination of eDNA and camera trapping proved essential for capturing the full extent of biodiversity impacts in post‐fire landscapes. Synthesis and applications . Our findings highlight the severe and lasting consequences of the 2020 wildfires, observed 2 years after the event, with habitat loss and direct mortality leading to population declines for both forest‐dwelling and open‐habitat species. The complementary use of eDNA metabarcoding and camera trapping enhances biodiversity assessments, though gaps in reference databases remain. These results emphasize the urgent need for adaptive management strategies to mitigate fire impacts, restore habitats and bolster the Pantanal's resilience. Effective governance, stakeholder collaboration and integrated fire management policies are crucial for safeguarding this globally significant wetland.