Unravelling the effect of climate change on fire danger and fire behaviour in the Transboundary Biosphere Reserve of Meseta Iberica (Portugal-Spain)

The impacts of wildfires are increasing in the Mediterranean Basin due to more extreme fire seasons featuring increasingly fast and high-intensity fires, which often overwhelm the response capacity of fire suppression forces. Fire behaviour is expected to become even more severe due to climate change. In this study, we quantified the effect of climate change on fire danger (components of the Canadian FWI System) and wildfire behaviour characteristics (rate of spread and fireline intensity) for the four major Mediterranean forest ecosystems located in the Transboundary Biosphere Reserve of Meseta Iberica under RCP4.5 and RCP8.5 scenarios. The effect of climate change on wildfire behaviour was supplemented by taking into account net primary production (NPP), hence fuel load. Our results show that the meteorological fire season will start earlier and end later, leading to a significant increase in the number of days with weather conditions that promote high-intensity wildfires, for both climate scenarios. Fuel type shapes how wildfire spread characteristics will unfold. The most relevant changes are projected to occur in pine forests, where a wildfire with median fireline intensity will offer serious resistance to control from spring to autumn. The severity of fire behaviour in shrublands also increases substantially when considering climate change, with high-intensity wildfires potentially occurring in any time of the year. Both deciduous and evergreen broadleaf forests are predicted to typically generate wildfires with low enough intensity to remain within suppression capability. By adjusting fuel load to future climate conditions, our results highlight that fireline intensity in deciduous and evergreen broadleaf forests may not increase during summer, and can even be significantly reduced in shrublands. This study suggests that improved fire planning and management of wildfire-prone landscapes will counteract the effect of climate change on fire behaviour and impacts.

Automated summary

The impacts of wildfires in the Mediterranean Basin are increasing due to more extreme fire seasons and high-intensity fires, which overwhelm fire suppression forces. This study quantified the effect of climate change on fire danger and wildfire behavior in Mediterranean forest ecosystems. The results show that climate change will lead to longer and more intense fire seasons, with significant increases in high-intensity wildfires. However, adjusting fuel load and improving fire planning and management can counteract the effects of climate change.