Wildfires as a major driver of landscape dynamics in three fire-prone areas of Portugal

Wildfires are a common event in Mediterranean landscapes. We assessed the implications of wildfires on the landscape dynamics of three fire-prone areas of Central and Northern Portugal during a time period of 13–15 years, starting in 1990. Using an information-theoretical approach and probability analysis, we assessed the relative importance of fire and initial land cover on the overall landscape dynamics. We further explored the role of fire on specific land cover dynamics by building transition matrices separately for burned and unburned areas. Finally we simulated future landscapes using the transition matrices to project landscape composition, according to a Markovian process. Fire had a determinant role in the landscape changes observed in the three study areas, as it favored shrubland persistence and the conversion of other land cover types to shrublands and mixed forests. The effect of fire on land cover dynamics could be explained mainly by post-fire vegetation responses due to land abandonment, but human-driven changes were also an important influence on land cover dynamics. In the long term, the current landscape dynamics would result in an increase in landscape diversity. When compared with this projection, either a scenario without fire or a complete periodic burn of the study areas, would result in lower landscape diversity. Comparing the two opposite scenarios, the latter would reduce the proportion of agriculture, while increasing the proportion of shrublands and unmanaged mixed forests of exotic and native species, therefore leading to an increase of fire hazard and to less sustainable landscapes.

► Logistic regression, transition matrices and Markov chains were used to assess the effect of wildfires on landscape dynamics.
► Wildfires strongly influenced landscape dynamics in the three study areas.
► Fire-driven transitions revealed land abandonment leading to a decrease of agriculture and an increase of shrublands and mixed forests of exotic and native species.
► In the three study areas wildfires are promoting more homogeneous and less sustainable landscapes.