FOREST ECOSYSTEM AREAS AFFECTED BY WILDFIRES: STATUS AND CHANGES

The time series of annual values of forest areas affected by large fires at national, regional and protected natural area levels have been analyzed using standard statistical methods (mean and linear regression), in order to assess the existence of trends, as well as variability and general characteristics of the phenomenon at different spatial scales.

Analysis of the time series of total burned areas provided by ISTAT since 2000 shows that 2007, 2017 and 2021 correspond to exceptional events (outliers) due to the overall extent of affected areas. For this reason, considering that the ratio between total and forest burned areas remains relatively stable, the year 2021 has been excluded from statistical analyses performed for trend assessment in the present indicator.

The stochastic component of the phenomenon, which affects the analysis, clearly emerges from the series. Therefore, the significance of trend results was primarily verified. Where no significant trend was observed, system status evaluation was discussed by comparing the current indicator value with the mean value over the considered period.

The methodology used to build the indicator since 2018 is based on evaluating burned areas by distinguishing between different forest ecosystem classes. To obtain a quantitative assessment of burned forest covers, polygons corresponding to areas burned as identified by EFFIS were combined with the distribution of forest categories obtained from the Ecosystems Classification Model - Forest4 (ECM-F4) developed by ISPRA. These forest classes follow the EUNIS (European Nature Information System – latest 2021 update) nomenclature at levels II and III:

• T1 – deciduous broadleaved forests (e.g., oak and beech forests);
• T2 – evergreen broadleaved forests (e.g., holm oak woods and Mediterranean scrub);
• T3 – coniferous forests (e.g., fir and pine forests);
• T34 – temperate sub-alpine forests (e.g., larch forests).

Forests not classified by the ECM-F4 model are included under code TNC (unclassified forest surface class). The EFFIS polygons and the other spatial datasets used were reprojected into a unified metric decimal coordinate system to calculate statistics for the various thematic classes. Annual values of burned area in the various classes were calculated at national and regional level, within protected natural areas of the EUAP network (Official List of Protected Areas) established by the State-Regions Conference resolution of December 17, 2009 (National Parks; Regional Parks; State Reserves; Regional Reserves), and within Natura 2000 sites: Special Areas of Conservation (SACs) and Special Protection Areas (SPAs).

The effects of wildfires were also considered for wetlands under the Ramsar Convention, old-growth forests, and biogeographical regions (alpine, continental, and Mediterranean).
Using specific spatial analysis tools on QGIS, the surface area of each forest class mapped by ECM-F4 for the identified intersection areas was calculated. Geostatistical processing was performed using GRASS GIS, Bash, R and QGIS software.
For protected natural areas, burned area estimates were carried out separately within each category. Indeed, overlapping institutional boundaries exist due to different administrative acts defining the EUAP and Natura 2000 networks, resulting in overlapping areas within and between the two systems. In this case, EFFIS polygons of burned areas were intersected (thematic overlay) with the polygons of the various considered themes, and then all areas belonging to the same type were merged to avoid double counting of the same surface.