Defoliation values indicate the level of resilience or susceptibility of tree species to the impact caused by atmospheric depositions and gaseous pollutants. Data collected over the past 27 years (1997–2023) show a fluctuating trend up until 2020, with alternating periods of mitigation and intensification of the phenomenon, as well as a greater sensitivity in broadleaved species. However, in the last three years (2021–2023), a worsening of the phenomenon has been recorded, with defoliation values reaching unprecedented levels. These values, exceeding 40% in 2021 and 2022, reached 45% in 2023 for both broadleaved and coniferous species. This suggests a worsening trend, which will need to be confirmed based on data from the coming years.

The phenomenon of forest fires analyzed based on data collected from 1970 to 2023 by the State Forestry Corps, now CUFA (Carabinieri Forestry, Environmental and Agri-food Unit Command), shows a fluctuating trend, with peak years (1993, 2007, 2017, 2021) alternating with years of decline (2013, 2014, 2018). The presence of fires within Protected Areas is high, with exceptionally large burned areas recorded in certain years, such as 2021 and 2022, when 26,507 hectares and 11,101 hectares were affected by fire, respectively.

The incidence of intentional fires is very high, accounting for approximately half of all recorded events and exceeding 60% in some years (2012, 2014, 2015, 2016, 2020).

The indicator analyzes the extent of forest areas affected by wildfires at the national, regional, and protected area scales between 2018 and 2023. The distribution and the surface of burned forested areas show significant annual variability. The 2023 ranks as the worst year after 2021, which was an exceptional year in terms of wildfire-affected forest ecosystems within the analyzed time series.

In 2023, the most affected regions were Sicily (10,080 hectares) and Calabria (2,987 hectares), which together accounted for 83% of the total forest nationwide area affected by wildfires. The most impacted forest classes are the evergreen forests (holm oak forests and Mediterranean scrub), followed to a much lesser extent by deciduous mixed forests (oaks and beech forests) and coniferous forests (pine, fir and larch forests).

Although the time series covers a short period, a linear regression analysis of the national forest cover affected by wildfires indicates an increasing trend. A statistically significant increasing trend has also been calculated for the regions of Sicily, Calabria, Apulia, and Aosta Valley over the considered period. A positive trend has also been observed for Regional Nature Reserves and those included in the Special Protection Areas (SPAs) and Special Areas of Conservation (SACs) within the Natura 2000 Network.