1. International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests)
Institute for World Forestry , December 2005.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

2. Political background
In the early 1980s a severe deterioration of forest condition was observed in large areas of Europe.
This became evident by means of increased defoliation of tree crowns.
Growing concern that the observed damage was caused by air pollution led in 1985 to the establishment of the “International Co-operative Programme on the Assessment and Monitoring of Air Pollution Effects on Forests” (ICP Forests).
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

3. Political background
ICP Forests was established under the Convention on Long-range Transboundary Air Pollution (CLRTAP) of the United Nations Economic Commission for Europe (UNECE).
CLRTAP provides an institutional framework that brings together science and policy by means of an international scientific cooperation and political negotiation platform.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

4. Political background
ICP Forests supplies CLRTAP with scientific data for international air pollution abatement policies.
Since 1991 ICP Forests has been cooperating closely with the European Commission (EC).
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

5. Political background
The lead country of ICP Forests is Germany. ICP Forests has been coordinated from the beginning on by the Federal Research Centre for Forestry and Forest Products (BFH) in Hamburg, Germany.
Today, 42 European countries participate in ICP Forests, including USA and Canada.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

6. Structure of ICP Forests
ICP Forests is supervised by its Task Force, in which all participating countries are represented. The Task Force is assisted by the Programme Coordinating Centre (PCC), by a Programme Coordinating Group (PCG), and by several Expert Panels and Working Groups.
The structure of these bodies and the related bodies of EU are shown in the following organigram.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

7. Structure of ICP Forests
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

8. Aims of ICP Forests The mandate of ICP Forests is:
to monitor effects of air pollution as well as other anthropogenic and natural stress factors on the condition and development of forests and to contribute to a better understanding of cause-effect relationships in forest ecosystem functioning.
ICP Forests aims to assess forest condition and its development in Europe, to relate it to environmental factors and to regularly inform policy makers, scientists and the public of the results.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

9. Aims of ICP Forests
Two main objectives are being pursued by the ICP Forests in
order to achieve this goal:
to provide a periodic overview on the spatial and temporal variation in forest condition in relation to anthropogenic and natural stress factors on an European and national large-scale systematic network (Level I).
to contribute to a better understanding of the relationships between the condition of forest ecosystems and stress factors, in particular air pollution, through intensive monitoring on a number of selected permanent observation plots spread over Europe (Level II).
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

10. Monitoring Level I
Level I is an extensive monitoring system that consists of a large number of plots on which monitoring of low intensity is conducted.
Stand and site characteristics are assessed prior to the surveys for each plot.
Main parameters to be assessed are:
Crown condition
Soil condition
Foliar condition
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

11. The surveys conducted are:
Monitoring Level I
The surveys conducted are:
Parameter
Assessment interval
Number of plots
crown condition
annually
6100
soil condition
once up to now
approx. 5300
foliar condition
approx. 1500
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

12. Monitoring Level I
The map shows the approximately 6000 permanent monitoring plots systematically arranged in a 16 x 16 km grid throughout Europe.
Some countries maintain denser networks in order to derive results at the national scale.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

13. Monitoring Level II
For intensive monitoring, more than 860 Level II plots have been selected, representing the major forest ecosystems of the countries that are actively participating.
A larger number of observations and measurements are made on these plots to investigate factors and processes at the ecosystem scale.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

14. The core surveys conducted are:
Monitoring Level II
The core surveys conducted are:
Survey
Frequency
Number of plots
crown condition
annually
866
soil condition
every ten years
865
foliar condition
every two years
855
tree growth
every five years
859
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

15. Monitoring Level II The complementary surveys conducted are: Survey
Frequency
Number of plots
ambient air quality
continuously
133
atmospheric deposition
499
soil solution chemistry
243
ground vegetation
every five years
730
meteorological condition
202
phenology
according to phenophases 59
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

16. Submission of data
In each country participating in the surveys a National Focal Centre (NFC) assesses the data and submits them to the PCC of ICP Forests.
The database management at PCC comprises: data validation, data correction in cooperation with the countries and data storage under a relational database management system.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

17. Data evaluation
PCC evaluates both the Level I and Level II data in cooperation with the Expert Panels of ICP Forests and related programmes under CLRTAP.
Reports are published annually by the BFH in cooperation with the UNECE.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

18. Results
When forest damage in Europe became obvious in the 1980s, its main symptom was defoliation of tree crowns.
Defoliation is a visible reaction on numerous environmental factors affecting tree vitality.
As it can be assessed with reasonable effort, it is used to trace the development of forest condition at the European-wide scale.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

19. Crown condition
This map represents the mean plot defoliation of all species in 2004.
Defoliation is particularly high in central and in parts of south eastern Europe.
Defoliation in 2004 was attributed largely to the severe heat and drought in the summer 2003.
More important than defoliation in a particular year is the development of defoliation over the time.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

20. Crown condition
The map shows the development of defoliation from 1997 to 2004.
Plots with increasing defoliation are distributed across Europe.
Decreasing defoliation is due to a recovery of Scots pine that started in Poland and continued in the Baltic States and Belarus.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

21. Crown condition
The following figure shows the development of defoliation of the main species since Most species have shown again increasing defoliation in the last 5 years.
The largest increase in mean defoliation was found for beech, holm-, sessile and European oak.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

22. Crown condition
Defoliation is mostly explainable by natural factors such as:
climatic stressors (heat, drought, frost and snow)
biotic stressors (insects and fungi)
The influence of air pollution is generally weak, but varies greatly with sites and tree species.
Following its mandate, ICP Forests pays particular attention to the effects of air pollution.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

23. Deposition
ICP Forests started to implement deposition measurements at Level II plots in the second half of the 1990s.
Deposition is measured in the open field (bulk deposition) as well as in the forest stands (throughfall).
Throughfall measurements have to be interpreted with care as rainwater washes certain elements from the tree foliage (leaching) and others are taken up by leaves and needles (canopy uptake).
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

24. Deposition
After intensive quality verifications, complete data sets for bulk deposition of nitrate (NO3), ammonium (NH4), and sulphate (SO4) were available for 169 plots over the years 1996 to 2001.
The figure shows the development of bulk deposition in this period and the notable decrease in SO4 in bulk deposition.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

25. Deposition
In addition, plot specific deposition means were calculated for NO3, NH4 and SO4 between the period of 1999 to 2000.
These plot specific values show clear spatial patterns.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

26. Sulphur deposition
Bulk SO4 deposition was particularly high in the eastern parts of central Europe. In these regions sulphate depositions ranged between 9.4 and 57.0 kg ha-¹ yr-¹.
Similarly high deposition in Belgium and the United Kingdom coincided with high sodium deposition, indicating deposition of sea salt.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

27. Sulphur deposition
Trends in bulk deposition show a significant decrease in sulphate depositions at 21.7% of the plots from 1996 to 2001.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

28. Nitrogen deposition
Plots with mean annual bulk deposition of nitrate above 5.0 kg ha-¹ yr-¹ are mostly situated in southernmost Norway and Sweden, in The Netherlands, Belgium, Germany, Switzerland and in northernmost Italy.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

29. Nitrogen deposition
Between 1996 and 2001 deposition of nitrate significantly decreased on 10.2% of the plots located mainly in Poland, Germany and Austria.
Trends in nitrogen deposition are partly correlated with trends in precipitation.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

30. Ammonium deposition
Plots with mean annual bulk deposition of ammonium above 8.7 kg ha-¹yr-¹ are located mainly in Poland, Belgium, The Netherlands, and north-western Germany.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

31. Ammonium deposition
Decrease in ammonium deposition was significant on a very small share of plots only.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

32. Ozone concentrations
Ozone (O3) concentrations were measured on more than 100 sites across Europe by means of passive samplers.
Passive sampling was made weekly, fortnightly or monthly between 2001 and 2003.
High solar radiation and high temperatures were observed to create high ozone concentrations.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

33. Ozone concentrations
Mean O3 concentrations from April to September 2002
The ozone concentrations were below 45 ppb on most of the measured sites.
However, the Mediterranean region shows a higher concentration of O3, between 45 and 60 ppb.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

34. Ozone concentrations
Mean O3 concentrations from April to September 2003
In the summer of 2003, O3 concentrations increased on most of the sampling sites of Italy due to high solar radiation.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

35. Ozone concentrations
During a three years‘ test phase, also a system was installed to detect ozone induced injury at plant leaves and needles.
The photos show typical symptoms.
Acer pseudoplatanus
Salix
caprea
Fagus sylvatica
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

36. Forest growth
Another indicator for forest condition is forest growth. Forest growth can be both increased and decreased by deposition.
The increase in forest growth observable over the last four decades may be the result of nitrogen deposition, increasing carbon dioxide (CO2) concentrations, increasing temperature and changes in silviculture.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

37. Forest growth
It has, however, been shown at Level II plots, that tree growth is lower on plots with higher defoliation.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

38. Political implications
The results published by ICP Forests in the last two decades provide a realistic picture of the extent and development of forest damage and constitute a part of the scientific basis of eight legally binding protocols under CLRTAP.
The following protocols were signed between 1984 and 1999 and consider the following issues:
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

39. Political implications
Long-term Financing of the Cooperative Programme for Monitoring and Evaluation of the CLRTAP
Reduction of Sulphur Emissions or their Transboundary Fluxes by at least 30%
Control of Nitrogen Oxides or their Transboundary Fluxes
Control of Emission of Volatile Organic Compounds or their Transboundary Fluxes
Heavy Metals
Persistent Organic Pollutants
Abatement of Acidification, Eutrophication and Ground-level Ozone
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

40. Political implications
Main results of CLRTAP protocols
are:
Emission reduction of 70% of SO4 and 25% of NO3 between 1980 and 2000.
Acidification is slowed but not stopped, critical loads are still exceeded at many sites.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

41. Political implications
The results of ICP Forests show that more efforts are needed to further reduce air pollution in Europe.
The next objective that is planned until 2010 is the emission reduction of SO2, NOx and NH3 by 60%, 40% and 17%, respectively compared to their values 1990.
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

42. Political implications
In future, the database and infrastructure of ICP Forests will also be used for contributions to environmental policy processes other than CLRTAP, for instance:
The Ministerial Conference on the Protection of Forests in Europe (MCPFE)
The Convention on Biological Diversity (CBD)
The United Nations Forum on Forests (UNFF)
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany

43. ICP Forests Programme homepage: www.icp-forests.org BFH homepage:
CLRTAP homepage:
Design & Layout: S.Schütt
Institute for World Forestry, BFH
Federal Research Centre
for Forestry and
Forest Products (BFH)
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Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstr. 91, D Hamburg, Germany