Extreme weather breaks phenological and landscape controls on temperate peatland fuel moisture; implications for carbon stock release through changing wildfire regimes

Temperate peatlands and heathlands are at increasing risk of severe wildfires under future climates which may combust legacy carbon stocks. The moisture content of the different fuel layers determines the threat posed. The controls on fuel moisture and their response to extreme weather have previously been unknown. Here, we show that controls differ between fuel layers. Fine dead fuel moisture is dominated by weather, live fuel by temporal controls including season and phenology, and soil organics by elevation and soil type. This separation of controls in time and space produces a landscape resistance to severe wildfire. However, extreme weather events break the phenological control on live fuel moisture and the landscape control of organics, resulting in low moisture content across all fuel types. This leads to the most severe conditions for fire ignition, spread and impact in traditionally non-fire prone regions, producing a landscape susceptible to severe environmental impacts and carbon emissions within a new summer wildfire regime.