Climate-driven upward spread of forest fires in European mountain regions

Forest fires are becoming increasingly frequent and seriously threaten European mountain regions. However, changes in the elevational distribution of forest fires in European mountain regions and their drivers remain largely unknown. Using remote sensing and climatic time series (2000–2022) combined with statistical approaches, we found that large forest fires (> 30 ha) are spreading upwards and are becoming more frequent at high elevations, notably from 2015 to 2022. Changes in burned area were mostly driven by climatic drivers (R² = 0.39), including vapor pressure deficit (VPD), soil moisture, and precipitation, suggesting that further warming could make European mountain regions increasingly fire prone. Whereas fires below 1,400 m occurred under a broad range of climatic conditions, fire occurrences above this threshold were enabled by extreme atmospheric aridity, underscoring that climate change is expanding fire into ecosystems historically buffered from burning. Our results indicate that understanding fire activity in mountain regions in the context of changing climate is essential for effective fire management and preservation of mountain ecosystem functions and services.