The role of dry and heat extremes on vegetation dynamics in the recent fire seasons in Southern Europe

Rural fires are recurrent in Southern Europe due to climate conditions, land use change, or a combination of both. Wet and mild winters and dry and warm summers favour the growth of vegetation and its subsequent low moisture content, increasing fuel availability. In Portugal, between 15 and 20 September 2024, severe wildfires burned more than 145,000 hectares and caused the death of more than 9 people. In Greece a major fire, stated as the largest recorded in the EU, started near the city of Alexandroupolis on August 21, with around 80.000 hectares burnt, mainly affecting the Dadia Forest and causing the death of almost two tens of migrants. Despite the crucial role played by dry fuel conditions fostering the propagation of wildfires, favourable meteorological conditions and fuel accumulation are related to the recorded fire activity and burned area. The influence of spring meteorological conditions on fire season burned area through their effect on fuel accumulation and dryness is assessed. The link between hot temperature and water availability in spring and the increased risk of summer flammability and fire spread through their influence on vegetation gross productivity is evaluated using satellite-derived data. The important role of fuel accumulation during the early growing season in fire-prone regions is highlighted in the case of Portugal in 2024 and Greece in 2023 and reinforces the crucial importance of fuel management for the definition of effective fire prevention measures in the context of warmer and drier conditions forecasted for southern European Countries.

Acknowledgements: This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025 and LA/P/0068/2020 https://doi.org/10.54499/LA/P/0068/2020 and also on behalf of DHEFEUS -2022.09185.PTDC and the project FAIR- 2022.01660.PTDC).