Panel 1
Stefania Ercole
Defoliation values indicate the level of resilience or susceptibility of different species to the impact of atmospheric deposition and gaseous pollutants.
Data collected over the past 28 years (1997–2024) show a fluctuating trend up to 2020, with alternating periods of decrease and increase in the phenomenon, and a greater sensitivity observed in broadleaved species. Starting in 2021, however, a worsening of the phenomenon was recorded, with exceptionally high defoliation levels never observed before.
In 2023, these values reached 45% for both broadleaved and coniferous species.
This deteriorating trend, which will need to be confirmed by future monitoring, slightly eased in 2024, when defoliation levels reached 35.6% in conifers and 43.3% in broadleaved species.
Impact indicator expressed through the annual average defoliation values of forest tree canopies (both coniferous and broadleaved species), recorded from 1997 to 2024 within a network of permanent monitoring areas identified as part of the National Integrated Program CON.ECO.FOR. (Forest Ecosystem Control), launched in 1995 by the State Forestry Corps and now carried out by the Carabinieri Command for the Protection of Biodiversity and Parks. Monitoring is conducted within permanent areas (254 Level I sites + 31 Level II sites) distributed across the national territory, representing Italy's main forest communities.
To provide information on the condition of the canopies of Italy's main broadleaved and coniferous forest species, in order to highlight their level of resilience or susceptibility to the impact caused by atmospheric depositions and gaseous pollutants.
The indicator complies with the requirements set by international agreements signed by Italy within the framework of ICP Forests (International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests), operating under the UNECE Convention on Long-range Transboundary Air Pollution (CLRTAP), and the MCPFE (Ministerial Conference on the Protection of Forests in Europe).
The CON.ECO.FOR. Program carries out forest monitoring activities based on the UN/ECE International Convention on Long-range Transboundary Air Pollution and in implementation of the EU regulation on forest monitoring and environmental interactions.
Panel 2
Ministry of Agricultural and Forestry Policies, 1999. CONECOFOR programme. First report 1999.
ANPA, 2000. Indicators of Sustainable Forest Management. State of the Environment Series 11/2000.
UNECE, BFH, 2005. The Condition of Forests in Europe, 2005 Executive Report.
https://www. carabinieri. it/arma/oggi/associazione/associazione-per-la-tutela-forestale-ambientale-e-agroalimentare/progetti-life
Defoliation values may be influenced by specific events not directly related to the impact of atmospheric pollutants. Therefore, these values alone may not be sufficient to provide a precise picture of the phenomenon.
Not foreseen.
Data quality assessment
Carabinieri Forestry, Environmental and Agri-Food Unit Command, SM - Projects Office, Conventions, Environmental Education, CON. ECO. FOR. Program (Forest Ecosystem Controls).
Request for data from the Carabinieri Forestry, Environmental and Agri-Food Unit Command, SM - Office for Projects, Agreements, Environmental Education, CON. ECO. FOR. Program (Forest Ecosystem Controls).
National
1997-2024
Indicator assessment
The indicator reports the percentage distribution of sampled trees within the permanent monitoring areas of the CON.ECO.FOR. Program, distinguishing between coniferous and broadleaved species. Monitoring is conducted within two networks of sampling areas:
- Level I network: 254 areas
- Level II network: 31 intensive monitoring areas
These areas are distributed across the national territory and represent Italy’s main forest communities.
Defoliation is assessed visually by trained personnel using dedicated reference manuals and is categorized into five classes:
- 0 = 0–10%, no damage
- 1 = >10–25%, slight damage
- 2 = >25–60%, moderate damage
- 3 = >60–<100%, severe damage
- 4 = 100%, dead trees
The temporal analysis of the phenomenon is based on the trends in the percentage of trees with defoliation greater than 25%.
The overall condition can be classified as poor, given the significant increase in defoliation observed from 2021 to the present, reaching levels never before recorded for both coniferous and broadleaved species (Figure 1, Table 1). Moreover, the percentage of trees showing a defoliation degree greater than 25% the established damage threshold—is sufficiently high to raise concern.
Between 1997 and 2020, total defoliation values averaged around 35%, with fluctuations across the years. The phenomenon worsened during 2017–2018 (reaching nearly 39%), then showed signs of improvement in 2019–2020, stabilizing at around 35–36%.
Defining a clear trend is difficult due to the oscillating nature of the phenomenon; however, since 2021 a marked deterioration has been recorded, indicating a negative trend. Defoliation levels exceeded 40%, a threshold never reached in the 28 years of monitoring (Figure 1, Table 1).
This worsening trend slightly eased in 2024, with defoliation values of 35.6% for conifers and 43.3% for broadleaved species. Therefore, the trend assessment will need to be confirmed or revised based on future data.
Data
Table 1: Percentage distribution of sampled trees by defoliation class and species category
State Forestry Corps until 2016, now Carabinieri Forestry, Environmental, and Agri-Food Unit Command, SM - Projects, Agreements, Environmental Education Office, CON.ECO.FOR. Program (CONtrolli ECOsistemi FORestali - Forest Ecosystem Controls)
Defoliation classes: Class 0: 0-10%, no damage; Class 1: >10-25%, slight damage; Class 2: >25-60%, moderate damage; Class 3: >60-<100%, severe damage; Class 4: 100%, dead trees
* The total values in brackets represent the percentage distributions of the total sample.
Figure 1: Annual trend in the percentage distribution of sampled trees for which a degree of defoliation > 25% (classes 2-4) was recorded.
State Forestry Corps until 2016, now Carabinieri Forestry, Environmental, and Agri-Food Unit Command, SM - Projects, Agreements, Environmental Education Office, CON.ECO.FOR. Program (CONtrolli ECOsistemi FORestali - Forest Ecosystem Controls)
Data collected over the last 28 years (1997–2024) from permanent monitoring plots across Italian forests, within the framework of the CON.ECO.FOR. Program, show a fluctuating pattern of defoliation, with broadleaved species displaying greater sensitivity up to 2020 (Figure 1).
From 2021 onwards, however, a clear deterioration has been observed, with defoliation levels reaching 45% in 2023 (Table 1).
When interpreting these results, it is important to consider that, beyond the impact of atmospheric deposition and gaseous pollutants, multiple stress factors may influence the vegetative condition of tree species—including climatic variability, pest outbreaks, and forest fires.