Panel 1
Stefania Ercole
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.
Impact indicator expressed through the annual average defoliation values of forest tree canopies (both coniferous and broadleaved species), recorded from 1997 to 2023 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
Ministero politiche agricole e forestali, 1999. Programma CONECOFOR. Primo rapporto 1999.
ANPA, 2000. Indicatori di Gestione Forestale Sostenibile. Serie Stato dell’Ambiente 11/2000.
UNECE, BFH, 2005. The Condition of Forests in Europe, 2005 Executive Report.
https://www.carabinieri.it/arma/oggi/organizzazione/organizzazione-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.
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Data quality assessment
Comando Unità Forestali, Ambientali e Agroalimentari Carabinieri, SM - Ufficio Progetti,Convenzioni, Educazione Ambientale, Programma CON.ECO.FOR.(CONtrolli ECOsistemi FORestali).
Data request to Comando Unità Forestali, Ambientali e Agroalimentari Carabinieri, SM - Ufficio Progetti, Convenzioni, Educazione Ambientale, Programma CON.ECO.FOR.(CONtrolli ECOsistemi FORestali).
National
1997-2023
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 status is poor, given the significant increase in defoliation in both broadleaved and coniferous species over the past three years, reaching over 40%, with a peak of 45% in 2023 (Figure 1, Table 1). The percentage of trees with defoliation exceeding 25%, which represents the damage threshold, raises serious concerns.
Between 1997 and 2020, total defoliation values averaged 35%, with fluctuations over the years. The phenomenon worsened in 2017-2018, reaching nearly 39%, but showed improvement in 2019-2020, stabilizing around 35-36% on average. Due to this fluctuating pattern, defining a long-term trend is complex. However, in the last three years (2021-2023), a marked deterioration has been recorded, indicating a negative trend, with defoliation values exceeding 40%—unprecedented in the 27 years of monitoring (Figure 1, Table 1). The trend assessment, currently based on the last three years, will need to be confirmed or revised with future data collection.
Data
Table 1: Percentage distribution of sampled trees by defoliation class and species category
State Forestry Corps until 2016, now Forestry, Environmental and Agri-food Carabinieri Unit Command, SM - Office of Projects,Conventions, Environmental Education, CON.ECO.FOR.(CONtrols ECOsystem FORestals) Program.
Defoliation classes: Class 0: 0-10%, no damage; Class 1: >10-25%, mild damage; Class 2: >25-60%, moderate damage; Class 3 : >60-<100%, severe damage: Class 4: 100%, dead trees
* Total values in parentheses represent percentage distributions over the total sample
Data collected over the last 27 years (1997-2023) from permanent monitoring areas across Italian forests within the CON.ECO.FOR. Program shows an historically fluctuating trend in defoliation, with broadleaved species exhibiting higher sensitivity (Figure 1). However, in the last three years, the situation has worsened, with defoliation levels reaching 45% in 2023 for both broadleaved and coniferous species (Table 1).
When evaluating these results, it is essential to consider that, in addition to the impact of atmospheric depositions and gaseous pollutants, multiple stress factors can influence vegetation conditions. These include climatic trends, pest attacks, and wildfires, all of which can significantly contribute to forest canopy decline.