Zones where urban land covers meet wildland areas have become a critical point of interaction between human settlements and natural ecosystems at risk of wildfire. These zones span diverse socioeconomic, governance, and ecological dimensions that are often not accounted for with frequently used methodologies. We developed and mapped a tri-dimensional Pyro-Socio-Ecological Zone (PSEZ) framework based on a suite of composite indicators that account for disparate Ecological, Socioeconomic, and Governance contexts in southern Italy (IT) and southern California (CA), USA. In CA, PSEZ with high governance consistently present a lower number of wildfires compared to PSEZ with low governance values. In IT, PSEZ with low governance indicate a lower number of wildfires and more burned area while PSEZ with high governance levels had more wildfires and less burned area. Overall, we found that the distribution of PSEZs and wildfire governance implications differed between CA and IT, underscoring greater spatial fragmentation, disparate contexts, and complex socio-ecological interactions in these peri-urban areas. Findings highlight that care is warranted when applying USA derived methods and concepts to fire-prone, landscapes in different geographies and contexts.

Understanding the relationship between heat wave occurrence and wildfire spread represents a key priority in global change studies due to the significant threats posed on natural ecosystems and society. Previous studies have not explored the spatial and temporal mechanism underlying the relationship between heat waves and wildfires occurrence, especially over large geographical regions. This study seeks to investigate such a relationship with a focus on 37 ecoregions within a Eurasia longitudinal gradient. The analysis is based on the wildfire dataset provided by the GlobFire Final Fire Event Detection and the meteorological dataset ERA5-land from Copernicus Climate service. In both cases we focused on the 2001-2019 timeframe. By means of a 12 km square grid, three wildfire metrics, i.e., density, seasonality, and severity of wildfires, were computed as proxy of fire regime. Heat waves were also characterized in terms of periods, duration, and intensity for the same period. Statistical tests were performed to evaluate the different patterns of heat wave and wildfire occurrence in the 37 ecoregions within the study area. By using Geographically Weighted Regression (GWR) we modeled the spatial varying relationships between heat wave characteristics and wildfire metrics. As expected, our results suggest that the 37 ecoregions identified within the Eurasia longitudinal gradient differ in terms of fire regimes. However, the occurrence of heat waves did not show significant differences among ecoregions, but a more evident variability in terms of relationship between fire regime metrics and heat waves within the study area. The outcome of the GWR analysis allowed us to identify the spatial locations (i.e., hotspot areas) where the relationship between heat waves and wildfires is positive and significant. Hence, in hotspots the presence of heat waves can be seen as a driver of wildfire occurrence in forest and steppe ecosystems. The findings from this study could contribute to a more comprehensive assessment of wildfire patterns in this geographical region, thus supporting cross-regional prevention strategies for disaster risk mitigation.

Background: Wildfires in Southern Europe arise from interacting climatic, ecological, and socio-ecological mechanisms. Drought enhances fuel desiccation, land cover change reshapes vegetation flammability, and the expansion of the wildland–urban interface (WUI) increases ignition pressure and exposure. Understanding how these drivers overlap spatially and temporally is essential to identify where reinforcing or decoupled processes shape wildfire dynamics. This study develops a spatially explicit framework integrating drought variability (Standardized Precipitation–Evapotranspiration Index, SPEI), Landscape Flammability Classes (LFC), and Wildland–Urban Interface (WUI) expansion to detect statistically supported hotspots and coldspots of wildfire occurrence across biogeographical regions. Methods: We analysed a 20-year dataset (2001–2020) at 12-km resolution, combining number of fire and fire size with long-term trends in three macro-drivers (SPEI, LFC, WUI). Temporal changes in wildfire parameters were estimated using generalized linear models with False Discovery Rate (FDR) correction. Trends in SPEI and WUI were assessed through Mann–Kendall and Kendall tau tests supported by Theil–Sen slope estimation, while LFC change was derived from land-cover transitions between 2000 and 2018. Finally, a spatial co-occurrence analysis classified each grid cell as a hotspot, coldspot, or mismatch area based on the degree of alignment between macro-driver trajectories and wildfire trends. Results: Significant and candidate hotspots were concentrated in the Anatolian, Continental, and Mediterranean bioregions, where over 30% of burned areas showed concurrent increases in drought intensity, landscape flammability, and WUI expansion. The Anatolian bioregion exhibited the strongest increases in WUI (+ 73.4%) and LFC (+ 67.2%), while the Continental region was dominated by widespread drying (90.5% of its area). Coldspots were mainly located in the Atlantic region, reflecting coherent declines in both wildfire parameters and macro-drivers. Mismatch zones, encompassing more than half of the burned area, revealed high spatial variability where fire dynamics diverged from macro-driver trends, indicating the influence of local-scale or non-mechanistic processes. Conclusions: The joint analysis of climate variability, fuel continuity and human pressures shows that wildfire patterns in Southern Europe depend on how the long-term trends of these macro-drivers align or decouple. Hotspots reveal regions where multiple drivers evolve in the same direction as wildfire activity, whereas mismatch areas highlight the role of local processes that interrupt large-scale relationships. The framework provides a quantitative basis for interpreting spatial heterogeneity in wildfire dynamics and supports integrated, multi-driver assessments for Mediterranean wildfire research.

Key message: Mediterranean forest stands manifest diverse flammability traits according to their potential ecological successional stage and promoting a gradient from flammable to less flammable ecosystem. From a general consideration of vegetation as ‘fuel’, it has been well proven that plant traits have the potential to promote the forest stand gradient from flammable to less flammable. While the ever-growing literature helps to assess the relationship between plants and their flammability at species level, at the landscape scale this relationship should be evaluated along with a variety of forest features such as structural and stand parameters and from the perspective of successional forest stages. To this end, we clustered several forest stands in Southern Europe (Apulia region, Italy), characterized by oaks, conifers, and arboreal shrub species, according to their flammability traits. We hypothesized that flammability traits change along different horizontal and vertical structural features of forest stands, shifting from high to low-flammability propensity. The results confirmed that forest stands with greater height and diameter classes are associated with traits with a low-flammability propensity. It is worth highlighting the importance of shrub coverage in differentiating the clusters denoting their strong influence in increasing fuel load (litter and fuel bed traits). Finally, our findings lead us to assume that high-flammability propensity traits are associated with typical pioneer successional stages, supporting the notion that later successional forest stands are less flammable and, therefore, that flammability decreases along with succession.