Increased vulnerability to wildfires and post fire hydro-geomorphic processes in Portuguese mountain regions: what has changed?

Abstract

The main objectives of this study were to understand the frequency of forest fires, post-fire off-site hydrological response and erosional processes from a social and ecological perspective in two basins located in the central cordillera, Portugal. It also discusses the driving forces that contribute towards increasing the social-ecological vulnerability of systems in the face of hazards and emphasizes the importance of learning from disasters. Based on the historical incidence of wildfires, it is possible to identify several areas affected by two, three or four fires, since 1975. Following the two major fires, in 1987 and 2005, flash floods, intense soil erosion and sedimentation processes were generated, causing severe damage. Significant socioeconomic, political and ecological changes have been affecting mountain regions in the last decades. Approximately 80% of the population and more than 90% of the livestock have disappeared, common lands have been afforested with Pinus pinaster, and several agricultural plots have been abandoned. These factors have all contributed towards creating non- or submanaged landscapes that have led to a dramatic increase in the magnitude and frequency of wildfires and to post-fire hydrological and erosional processes when heavy rainfall occurs. Moreover, the low population density, high level of population ageing and very fire-prone vegetation that now covers large areas of both basins, contribute to a situation of extreme socio-ecological vulnerability, meaning that disasters will continue to occur unless resilience can be restored to improve the capacity to cope with this high susceptibility to hazards.