COMMUNICATION FROM THE COMMISSION

Commission Notice (1) on ecosystem monitoring under Article 9 and Annex V of Directive (EU) 2016/2284 of the European Parliament and of the Council on the reduction of national emissions of certain atmospheric pollutants (NEC-Directive)

(2019/C 92/01)

1.   Introduction and legal basis

The aim of this guidance is to address the key questions that Member States may have with regard to the practicalities of setting up and operating a network of monitoring sites that meets the requirements of Article 9 of Directive (EU) 2016/2284 (NEC-Directive) (2). As guidance, this document is not of a legally binding nature, and Member States have the flexibility to set up their networks as appropriate and practical for their domestic circumstances, as long as they ensure the monitoring of air pollution impacts as required by Article 9. When reporting their networks, Member States are encouraged to submit a document explaining how the networks have been developed to fulfil the requirements of the NEC-Directive.

Both Directive 2001/81/EC (3) (‘old NEC-Directive’) and Directive (EU) 2016/2284 (‘NEC-Directive’) have the aim to improve not only human health but also the condition of ecosystems across the EU. The Clean Air Programme for Europe (4) includes, in addition to its target for reduction of health impacts across the Union, a target for a reduction by 35 % of the ecosystem area subjected to eutrophication by 2030, compared with 2005.

The determination of the extent of ecosystem impacts of air pollution in the EU is based on exceedance of critical loads and levels for sulphur, nitrogen and ozone based on predominantly long range transport of pollutants. The calculation of these effect thresholds has relied on the work of the Working Group on Effects under the Gothenburg Protocol to the Convention on Long-Range Transboundary Air Pollution (LRTAP Convention (5)), including the work of the Coordinating Centre for Effects (CCE) and the International Cooperative Programmes (ICPs) on Waters, Forests, Vegetation, Integrated Monitoring (6), and the monitoring networks established for that purpose in the area of participating Parties to the Gothenburg Protocol.

Given the central importance of this work for the ecosystem objectives of the EU air policy, and to assess the effectiveness of the national emission reduction commitments, the co-legislators have included in the NEC-Directive provisions requiring the monitoring of the ecosystem impacts of air pollution. The mandatory monitoring is furthermore intended to reinforce the work being done under the LRTAP Convention.

The principal obligations on Member States under the NEC-Directive are as follows:

—

To ensure the monitoring of negative impacts of air pollution upon ecosystems based on a network of monitoring sites that is representative of their freshwater, non-forest natural and semi-natural habitats, and forest ecosystem types, taking a cost-effective and risk-based approach (Article 9 ( 1) first subparagraph);

—	To report by 1 July 2018 and every four years thereafter, to the Commission and the European Environment Agency, the location of the monitoring sites and the associated indicators used for monitoring air pollution impacts (Article 10(4)(a));

—	To report by 1 July 2019 and every four years thereafter, to the Commission and the European Environment Agency, the monitoring data referred to in Article 9 (Article 10(4)(b)).

The Commission shall:

—	Report by 1 April 2020 and every four years thereafter, to the European Parliament and the Council, on the progress towards the Union's biodiversity and ecosystem objectives in line with the 7th Environment Action Programme (7th EAP) (7) (Article 11(1)(a)(iii)) (see section 2 for details).

The establishment of a fully operational network for air pollution impact monitoring is a matter of incremental improvement. This guidance focuses on the key issues for the first reporting cycles (2018 and 2019). On the basis of the information reported by the Member States under Article 10 the Commission will, in its report to be published in 2020 under Article 11 of the NEC-Directive, assess to what extent the monitoring networks established so far would need to be reinforced in order to meet the requirements of Article 9. Based on that assessment and on any other issues or lessons learned that will have emerged in the course of the implementation process, it will be assessed whether further improvements in the monitoring are needed. Those improvements should then be implemented, to the extent possible, for the second reporting cycle (2022 and 2023).

This guidance is structured as follows:

—	Section 2: Objectives of ecosystem monitoring under the NEC-Directive

—	Section 3: Scope and design of the ecosystem monitoring network

—	Section 4: Relationship with other monitoring activities

—	Section 5: Reporting

—	Section 6: Support for implementation

—	Section 7: Case studies

2.   Objectives of ecosystem monitoring under the NEC-Directive

The objective of the ecosystem monitoring scheme is to provide the knowledge base for the assessment of the effectiveness of the NEC-Directive in protecting the environment. With regard to the protection of the environment, the Directive (Article 1 and Article 11) refers to ‘the Union's biodiversity and ecosystem objectives in line with the 7th EAP’, which in relation to air pollution are defined as follows: ‘air pollution and its impacts on ecosystems and biodiversity are further reduced with the long-term aim of not exceeding critical loads and levels’ (8).

The intention is thus to reinforce an ecosystem monitoring network needed to determine the state of, and predict changes in, terrestrial and freshwaters ecosystems in a long-term perspective with respect to the impacts of sulphur oxides (SOX), nitrogen oxides (NOX), ammonia (NHy), and ground level ozone (i.e. acidification, eutrophication, ozone damage or changes in biodiversity). Thus the ultimate objective of the monitoring is to improve information on the impacts of air pollution on terrestrial and freshwater ecosystems, including the extent of any impacts and the ecosystem recovery time when the impacts are reduced, and to contribute to a review of critical loads and levels.

To work towards these objectives, Member States shall coordinate with other monitoring programmes in their territory and across the European Union, and under the LRTAP Convention if appropriate. The ecosystem monitoring currently implemented under the Birds (9), Habitats (10) and Water Framework (11) Directives involves a wide-ranging reporting network on the overall state of ecosystems, but air pollution impacts are not monitored under these Directives. Therefore, data concerning ecosystem condition collected under these broad-based assessments will be only partially relevant to the objectives of Article 9 (this issue is taken up in more detail in section 4 below, on ‘Relationship with other monitoring activities’). The NEC-Directive monitoring follows the LRTAP Convention effects monitoring in being specifically related to investigating the impacts of air pollution as a pressure on ecosystems, with a view to better understanding the mechanisms involved, the extent of impacts and the recovery prospects. The ecosystem monitoring under the LRTAP Convention is therefore directly relevant to the NEC-Directive objectives.

3.   Scope and design of the ecosystem monitoring network

3.1.    The impacts of interest

The air pollution impacts of interest for the ecosystem monitoring are in the first instance those relating to the substances for which reduction commitments are set in Annex II to the Directive (i.e. SO2, NOX, NMVOC, NH3 and PM2,5), that is: acidification, eutrophication, and ozone damage to vegetation growth and biodiversity. While the impacts of other pollutants (e.g. heavy metals) are also of concern, a stepwise approach is appropriate and it is proposed that the first phase of monitoring focus on these three impacts.

3.2.    Ecosystem types

Article 9(1) of the NEC-Directive requires that Member States conduct monitoring on the basis of: ‘a network of monitoring sites that is representative of their freshwater, natural and semi-natural habitats and forest ecosystem types, taking a cost-effective and risk-based approach’.

There is a large number of ecosystem types distributed throughout Europe (12) with a significant variation in the number of ecosystem types per Member State. While the network coverage must be representative of the ecosystems existing in their territories, Member States should take a cost-effective and risk-based approach as provided in Article 9(1) of the NECD when choosing the number and locations of the sites and the kind of indicators monitored.

A starting point for identifying a representative number of ecosystems and their habitats to be monitored is the number of biogeographical regions in each Member State. The latest classification of the EU's biogeographical regions comprises eleven areas (Alpine, Anatolian, Arctic, Atlantic, Black Sea, Boreal, Continental, Macaronesian, Mediterranean, Pannonian and Steppic) shown in Figure 1 below.

Ideally, at least one monitoring site should be established for each ecosystem type in a biogeographical region.

Figure 1

Biogeographical regions in Europe (1)

(1)	https://www.eea.europa.eu/data-and-maps/data/biogeographical-regions-europe-3

Within each biogeographical region, the main ecosystems and habitats of interest can be classified according to the MAES (13) and EUNIS (14) classifications. The proportion of area covered by each MAES ecosystem type varies substantially (Figure 2) within a country and in the EU as a whole, and there is also substantial variation between countries.

Figure 2

Area and percentage of MAES terrestrial and freshwaters ecosystem types EU-28 (MAES, 2016 (1))

(1)	MAES Technical Report 2016-095 ‘Mapping and assessing the condition of Europe's ecosystems: Progress and challenges. 3rd Report – Final, March 2016’.

Some ecosystem types under the MAES classification are clearly not relevant for the NEC-Directive purposes (principally urban ecosystems and most of sparsely or unvegetated land). As regards cropland, nutrient load by air pollution is less relevant compared to fertilisation and other measures, however the fact that crops are sensitive to ozone justifies monitoring.

On that basis, six major categories of ecosystems are relevant for the NEC-Directive: Grasslands, Cropland, Forests and Woodlands, Heathland and Shrub, Wetlands, and Rivers and Lakes, as shown in Table 1. These MAES categories can be easily linked with EUNIS habitat classes (Level 1 and 2) and Corine Land Cover (15) classes (Level 3) at the respective level of available information from the general Level 1 to the more detailed Level 3 or higher. Specific ecosystems and habitats of special interest or high importance and value can be integrated into the monitoring scheme, linking them to these categories.

Table 1

Overview of ecosystems and habitats and link between MAES ecosystem types, EUNIS habitat classes and Corine Land Cover classes

MAES Ecosystem type	EUNIS Habitat classes Level 1	EUNIS Habitat classes Level 2	Corine Land Cover (CLC) classes Level 3
Cropland	I Regularly or recently cultivated agricultural, horticultural and domestic habitats	I1 Arable land and market gardens I2 Cultivated areas of gardens and parks	2.1.1. Non-irrigated arable land 2.1.2. Permanently irrigated land 2.1.3. Rice fields 2.2.1. Vineyards 2.2.2. Fruit trees and berry plantations 2.2.3. Olive groves 2.4.1. Annual crops associated with permanent crops 2.4.2. Complex cultivation patterns 2.4.3. Land principally occupied by agriculture, with significant areas of natural vegetation 2.4.4. Agro-forestry areas
Grassland	E Grasslands and land dominated by forbs, mosses or lichens	E1 Dry grasslands E2 Mesic grasslands E3 Seasonally wet and wet grasslands E4 Alpine and subalpine grasslands E5 Woodland fringes, clearings and tall forb stands E6 Inland salt steppes E7 Sparsely wooded grasslands	2.3.1. Pastures 3.2.1. Natural grassland
Woodland and forest	G Woodland, forest and other wooded land	G1 Broadleaved deciduous woodland G2 Broadleaved evergreen woodland G3 Coniferous woodland G4 Mixed woodland G5 Lines of trees, small woodlands, recently felled woodlands, early stage woodland, coppice	3.1.1. Broad-leaved forest 3.1.2. Coniferous forest 3.1.3. Mixed forest 3.2.4. Transitional woodland shrub
Heathland and shrub	F Heathland, scrub and tundra	F1 Tundra F2 Arctic, alpine and subalpine scrub F3 Temperate and mediterraneo-montane scrub F4 Temperate shrub heathland F5 Maquis, arborescent matorral and thermo-Mediterranean brushes F6 Garrigue F7 Spiny Mediterranean heaths F8 Thermo-Atlantic xerophytic scrub F9 Riverine and fen shrubs FA Hedgerows FB Shrub plantations	3.2.2. Moors and heathland 3.2.3. Sclerophyllous vegetation
Wetlands	D Mires, bogs and fens	D1 Raised and blanked bogs D2 Valley mires, poor fens and transition mires D3 Aapa, palsa and polygon mires D4 Base-rich fens and calcareous spring mires D5 Sedge and reedbeds, normally without free-standing water D6 Inland saline and brackish marshes and reedbeds	4.1.1. Inland marshes 4.1.2. Peatbogs
Rivers and lakes	C Inland surface waters	C1 Surface standing waters C2 Surface running waters C3 Littoral zone of inland surface waterbodies	5.1.1. Water courses 5.1.2. Water bodies
Source: http://ec.europa.eu/environment/nature/knowledge/ecosystem_assessment/pdf/MAESWorkingPaper2013.pdf

3.3.    Site selection, number and density

Given the variety of conditions as regards air pollution load and the biological, chemical and physical characteristics of each ecosystem type across the EU, this section focuses on providing qualitative criteria for site selection that are relevant for each type of ecosystem. These criteria should be the basis for selecting sites and determining their number and density to ensure a sufficient and consistent monitoring network specific to the situation of the individual Member States. It should be kept in mind that the selection of sites is a multi-criteria process which may vary between Member States.

Where possible the sites chosen should satisfy the following principles:

—	the site should be typical for the ecosystem type to be monitored;

—	the site should be such that the impacts of aerial deposition can be distinguished from other pressures;

—	the site should be sensitive to the pressure in question, such that if there are any impacts they would be readily identifiable.

Maps of areas sensitive to particular impacts can be useful when selecting monitoring sites.

Biodiversity should be another selection criterion for monitoring sites to address the cause-effect relationships of pollution on biodiversity. While not every site has to be necessarily of high biodiversity value, the network as a whole should ensure an adequate representation of sites that are minimally disturbed by management and preferably rich in species, which may for example be found in Natura 2000 areas, nationally designated areas (CDDA) or other protected sites.

Overall, the required number and density of sites are dependent on the sensitivity of the ecosystems, the ecosystem types affected, the number of different ecosystem types occurring in the different biogeographical regions (see section 3.2 above), and the intensity of the air pollution pressures. The national network should be such as to allow for analysis of spatial gradients and understanding of cause-effect relationships, and should provide data for mapping and modelling of critical loads, and levels and exceedances. It is more important to have sites in several regions than to have several sites in each region. More pristine areas need fewer sites when no major changes are anticipated in those regions, but they should not be omitted.

With regard to natural environmental conditions, the most important gradients found in the Member States should be covered by the network. Key climatological parameters (precipitation, temperature), hydrological parameters and soil alkalinity (e.g. pH) gradients should vary systematically. This information is partly inherent in the respective biogeographical regions (see section 3.2) and can be further specified with maps with more detailed classification of environmental strata (e.g. Metzger et al. 2005 (16)).

With regard to air pollution parameters, each Member State should at least cover areas with high deposition levels of acidifying and eutrophying substances (on a national scale) and high concentration levels of ozone. For long-term comparisons, reference sites at low deposition/concentration values should also be selected. The use of existing maps of critical load/level exceedance for site selection is recommended.

With regard to ecosystem types, each Member State should select sites according to their representativeness within its territory (see Table 1). Additionally, Annex I of the Habitat Directive (92/43/EEC) can be used for selecting habitats according to their relevance.

Taking into account the distribution of sensitive ecosystems and the resources needed for taking the necessary measurements to assess air pollution impacts, a tiered approach may be appropriate, with wide-ranging monitoring of a relatively simple parameter set (Level I) reinforced by more targeted and in-depth monitoring of a smaller set of more sophisticated parameters (Level II). For some ecosystems, it may be appropriate to use a minimum density of sites for Level I-type monitoring (for instance Level I monitoring under the ICP Forests uses a network based on a 16 × 16 km grid). Where appropriate, such level distinction is made in the recommendations below on parameters and monitoring frequency.

3.4.    Parameters to be monitored and frequency of monitoring

This section of the guidance elaborates on the parameters that would be appropriate for monitoring, reflecting the ones described in Annex V to the NEC-Directive, which sets out optional indicators for monitoring air pollution impacts. It presents recommendations for monitoring acidification and eutrophication based on experience and previous activities of the ICPs for forest and woodlands, and freshwater ecosystems, as well as for monitoring ozone damage covering all terrestrial ecosystems. It also refers to the integrated monitoring sites of the ICPs which offer information on both ecosystem specific impacts and separation of effects of air pollution from other impacts, especially for freshwater ecosystems. It is mostly based on the related manuals of the ICPs and the LRTAP Convention, acknowledging implemented scientifically-approved methods and long-term experience in pollution impact monitoring, which have also been further reviewed by the NEC-Directive expert group. But reporting should also cover ecosystems which are not monitored under the ICPs so far, mainly grassland, heathland and other natural or semi-natural ecosystems of high importance. The overall list of parameters proposed to be considered for monitoring pursuant to Article 9 of the NEC-Directive is listed in the template for reporting as from 1 July 2018 and respective documents (17).

The following sections 3.4.1 to 3.4.4 provide short overviews on relevant parameters, building on the existing monitoring systems of the ICP as developed under the LRTAP Convention. In terms of acidification and eutrophication, these systems have been developed only for forests and woodlands and freshwater so far. Monitoring of ozone impacts has mainly focused on cropland.

Slightly reviewed and adjusted, these sections can be used as guidance for monitoring the other ecosystems and habitats requested under Article 9 of the NEC-Directive, such as grasslands, heathlands and other natural or semi-natural ecosystems. Natural and semi-natural ecosystems in specific areas such as urban and peri-urban or coastal areas can also be included as they are of special interest for related policies of Member States.

As further outlined in section 4, data and information from other monitoring networks can be integrated to improve cost-effectiveness and avoid parallel work. Action 5 of the EU Biodiversity Strategy to 2020, MAES (Mapping and Assessment of Ecosystems and their Services), especially in its 5th Report (18), provides additional information on how to measure and assess ecosystem conditions and the related indicators which can be used.

3.4.1.   Terrestrial ecosystems: Forests and woodlands under ICP

Table 2 below sets out the parameters and their monitoring frequencies at Level I and Level II type plots (19) for forest ecosystems, according to the ICP Forests approach and with due regard to Annex V of the NEC-Directive. Detailed description of all methods applied to monitor the condition of forest ecosystems at both Level I and Level II intensity are given in an extensive manual (20), and references to the relevant sections of the manual are provided in the table below, also with regard to the data that should be reported. An overview on surveys carried out under the ICP Forests, and the respective parameters of the full programme can be found in that manual and on the internet (http://icp-forests.net/).

Table 2

Selected indicator complexes, parameters, and sources for methods from the ICP Forests to complement optional indicators in Annex V to the NEC-Directive

Measurement (Indicator complex)	Parameters	Frequency	Methods
Soil acidity in the soil solid phase	Element concentrations (base cations etc.) Ca, Mg, K, Na, Alex, Ntot and ratios C/N	Every 10-15 years at Level I and Level II plots	Part X
Soil acidity in the soil solution	pH, [SOx] (*1), [NO3], [base cations (Ca, Mg, K, Na)], [Alex].	Every 4 weeks at Level II plots	Part XI
Soil nitrate leaching, in soil solution	[NO3+] at deepest soil layer (40-80 cm); to calculate fluxes a soil water flux model (water balance model) has to be applied.	Every 4 weeks at Level II plots	Part X, water balance model cf. Part IX
C/N ratio + total soil N, in soil solid phase	Cstock, Nstock, C/N ratio.	Every 10-15 years at Level I and Level II plots	Part X
Nutrient balance in foliage	[N], [P], [K], [Mg], and ratios with [N].	Every 2 yrs. at Level II, every 10-15 yrs. at Level I plots	Part XII

Additional parameters covering other important features and properties of forest ecosystems, like stand age, tree species and ground vegetation composition and diversity, crown condition, leaf area index (LAI), throughfall chemistry, litterfall amount and chemistry, or the composition of epiphytic lichens (on tree trunks) are important and may complement the optional indicators set out in Annex V of the NEC-Directive. Respective methods are given in the respective parts of the ICP Forests manual as well.

At some ICP Forests sites, but also at other forest and terrestrial ecosystem sites, the nitrogen concentration in mosses is monitored every five years (in addition to heavy metals and selected persistent organic pollutants) and reported to the ICP Vegetation (manual available from http://icpvegetation.ceh.ac.uk).

3.4.2.   Freshwater ecosystems: Rivers and lakes under ICP

Surface waters, such as rivers and lakes, are in many cases the first medium in the ecosystem that reacts to acidification and eutrophication. Acid sensitive catchments with thin, highly siliceous soils and little ability to retain sulphate and nitrate, are found in upland areas in many parts of Europe. Populations of fish and other aquatic organisms have been severely damaged over the past 100-years. In many rivers and lakes, fish stocks have been lost because of transboundary air pollution. Sulphate, nitrate, alkalinity, pH and aluminum levels in sensitive waters respond quickly to change in emissions, with subsequent effects on sensitive organisms and thereby the whole ecosystem. Such effects are evident at distances both relatively close and far from major emissions. As emissions started to decrease in the 1980s, the water chemical indicators rapidly started to show signs of recovery whereas biological recovery has lagged behind. More recently, it has also emerged that nitrogen deposition can have a fertilizing effect (eutrophication) in some surface waters found in pristine areas far from direct human disturbance. Increasing atmospheric nitrogen loads could therefore change the functioning of the aquatic food web with potentially serious consequences. Water chemistry and biology in surface waters are among the best indicators of the effects of air pollution and its mitigating measures on ecosystems in Europe.

A programme designed for monitoring effects of sulphur and nitrogen deposition in freshwaters should as a minimum include the parameters listed in Table 3. The frequency of sampling should reflect temporal variation in the site that is monitored. Sites where the water is exchanged rapidly will respond more quickly to changes in deposition. ICP Waters recommend that fast-flushing lakes and rivers should at least be sampled monthly (ICP Waters, 2010). Quarterly or seasonal sampling can be adequate in lakes where the water has a theoretical residence time longer than a few months. Biological monitoring of sensitive species or communities in at least some of the selected sites is highly recommended (Table 4).

Other physical and chemical parameters such as temperature, water flow, aluminum fractions, total nitrogen and phosphorous provide supplemental information that, depending on local conditions, can be useful, e.g. for interpreting biological effects of air pollution.

Table 3

Rivers and lakes: Recommended minimum parameters, chemistry under the ICP Waters

Details and further explanation can be found in the ICP Waters manual (ICP Waters, 2010). The references are to chapters in the manual.

Measurement	Parameters	Frequency	Method	Data to be reported
Lake catchment sensitivity and hydrochemical effects of air pollution (acidification)	Alkalinity, sulphate, nitrate, chloride, pH, calcium, magnesium, sodium, potassium, dissolved organic carbon, and specific conductivity	Seasonal/quarterly to annual, depending on flush rate	Grab sampling of the upper layer (0,1-1 m) or lake outlet. Described in chapter 3.	Major ions (mg/l), nitrate (μg N/L), pH, DOC (mg C/l), alkalinity (μeq/L), conductivity at 25 °C (μS/cm)
River/stream catchment sensitivity and hydrochemical effects of air pollution (acidification)	Alkalinity, sulphate, nitrate, chloride, pH, calcium, magnesium, sodium, potassium, dissolved organic carbon, and specific conductivity	Monthly	Grab sampling. Described in chapter 3.	Major ions (mg/l), nitrate (μg N/L), pH, DOC (mg C/l), alkalinity (μeq/L), conductivity at 25 °C (μS/cm)

Table 4

Rivers and lakes: Recommended additional parameters, biology under the ICP Waters

Details and further explanation can be found in the ICP Waters manual. The references are to chapters in the manual.

Measurement	Parameters	Frequency	Method	Data to be reported
Biological indicators of air pollution (acidification). Benthic invertebrates in rivers and lakes.	Presence/absence or relative abundances of particular groups/species	Seasonal to annual	Kick samples, littoral sampling or core samples. See Chapter 4. WFD methods are based on CEN and ISO-standards, and these are adequate.	Qualitative or quantitative data. http://www.icp-waters.no/data/submit-data/
Other groups such as fish, diatoms and periphyton can also be used as bio-indicators of acidification.

3.4.3.   Terrestrial ecosystems: ozone damage under ICP

Monitoring of ozone damage poses challenges specific to that pollutant. Deposited sulphur and nitrogen compounds remain in freshwater and terrestrial ecosystems in both vegetation and soil in some chemical form that can be monitored, including concentrations in plants and mosses (see Tables 3 and 4). In addition, sulphur and/or nitrogen deposition leads to acidification of freshwaters and soils that can be monitored. In contrast, ozone itself does not accumulate in vegetation or soil; it is the breakdown products of ozone inside plants and the reactions of the plants to these that cause the damage.

Excessive exposure to ground-level ozone has harmful effects on many types of vegetation, affecting terrestrial ecosystems and the services they provide (e.g. food and timber production, carbon sequestration, air quality and climate regulation). The effects on ozone-sensitive species include visible foliar damage, a reduction in growth, yield quality and quantity for crops, flower number and seed production, and enhanced vulnerability to abiotic stresses such as frost or drought, and biotic stresses such as pests and diseases.

The only visible damage in terrestrial ecosystems that can be attributed directly to ozone is foliar damage. Ozone-specific foliar damage develops in ozone-sensitive species during days with high ground-level ozone concentrations. However, there is no clear relationship between ozone foliar damage and impact on important vegetation parameters such as growth (e.g. tree growth) or yield (in the case of crops). For leafy vegetables, the marketable value will be reduced if visible foliar damage is present. Based on experimental data, critical levels of ozone have been established for parameters such as tree biomass and crop yield as these represent cumulative effects of seasonal exposure to ozone.

Critical levels of ozone are defined as the cumulative exposure or cumulative stomatal flux of atmospheric pollutants above which direct adverse effects on sensitive vegetation may occur according to present knowledge. Ozone critical levels and target values established for the protection of vegetation in European Legislation (Directive 2008/50/EC (21)) are based on the cumulative ozone concentration. More recent research has shown that cumulative stomatal ozone flux-based target values (e.g. the indicator Phytotoxic Ozone Dose (POD)) are biologically more relevant than concentration-based target values (e.g. AOT40) as they provide an estimate of the amount of ozone entering the leaf pores (stomata) and resulting in damage inside the plant (Mills et al., 2011a,b). The methodology for calculating POD has been developed and applied by the ICP Vegetation using the DO3SE model. By monitoring hourly ozone concentrations and meteorological parameters (Table 5), cumulative stomatal ozone fluxes can be calculated for specific plant species. Exceedance of the stomatal flux-based critical levels provides an indication of the risk of ozone impact on ozone-sensitive species at the site. Details on the calculation of POD and its application are available in the Manual on methodologies and criteria for modelling and mapping critical loads and levels and air pollution effects, risks and trends (22).

Table 5

Indicators for assessing ozone damage to vegetation according to Annex V of the NEC-Directive

Details and further explanation can be found in the indicated ICP manuals.

Indicator	Measurement	Frequency	Reference for methodology and data reporting
Ozone foliar damage to trees	Visible ozone symptoms in leaves of tree species and on trees and wood plants at ‘light exposed sampling sites’ (LESS); Tree diameter growth.	Visible ozone symptoms: annually at Level II plots; Diameter growth: every 5 yrs.	Part VIII (visible ozone symptoms) and Part V (diameter growth) of ICP Forests Manual
Ozone foliar damage to crops and non-tree species	Visible ozone symptoms in leaves; Crops: harvested yield	Visible ozone symptoms: at least annually during growing season, preferably just after (3-7 days) an ozone episode (1); Crop yield: annually	http://icpvegetation.ceh.ac.uk. To be revised from past manuals to suit NEC-Directive (including lists of ozone-sensitive species)
Exceedance of flux-based critical levels of ozone	Ozone concentration (2), meteorology (3) (temperature, relative humidity, light intensity, rainfall, wind speed, atmospheric pressure) and soil type (sandy, clay or loam) at or near site (4). Flux-based model DO3SE can be used to calculate ozone flux and exceedance of critical levels	Every year: Hourly data during growing season (5)	Method in Modelling and Mapping Manual LRTAP Convention, Chapter 3 – ‘Mapping critical levels for vegetation’ (http://icpvegetation.ceh.ac.uk, including link to online version of the DO3SE model (6)).

3.4.4.   Integrated monitoring of freshwater and terrestrial ecosystems under ICP

Integrated monitoring of ecosystems refers to in-depth, simultaneous measurement of physical, chemical and biological properties of a catchment, over time and across compartments. Due to its complexity, integrated monitoring does not aim to cover large spatial areas but rather to improve the causal understanding of the link between air, soil, water and biological response predominantly in forested ecosystems. As such these monitoring areas could provide, on the one hand, ecosystem specific data, e.g. for forest or freshwater ecosystems and, on the other hand, could allow better distinction between air pollution related impacts compared to other possible sources of pollution. Generally, Member States have a few locations in which this detailed monitoring is carried out. Member States are recommended to have at least two sites covering relevant climatic and deposition gradients. Integrated monitoring sites should be small, well defined catchments in natural or semi-natural areas. Measurements include meteorology, wet and dry deposition, throughfall, soil chemistry (solid and liquid phase), surface and groundwater chemistry, and biological response (i.e. vegetation and other biological elements). The aims are to monitor and assess both biogeochemical trends and biological responses; to separate noise and natural variation from the signal of anthropogenic disturbance by monitoring natural forest ecosystems; and to develop and apply tools, e.g. models, for regional assessment and prediction of long-term effects.

Table 6 provides variables relevant under Annex V to the NEC-Directive and the effects of air pollution on ecosystems. Detailed description of needed equipment, design and methodologies can be found in the ICP Integrated Monitoring manual (23). The full comprehensive measurement programme allows also detailed modelling, cause-effect analysis, and studying interactions with climate change processes (24) (25) (26).

Table 6

Parameters and frequency for the ICP Integrated Monitoring sites

Detailed description and methodology can be found in the ICP Integrated Monitoring manual  (27).

Measurement (Indicator complex)	Parameter	Frequency	Method
Meteorology	Precipitation, temperature of the air, soil temperature, relative humidity, wind velocity, wind direction, global radiation/net radiation	Monthly	Part 7.1
Air chemistry	sulphur dioxide, nitrogen dioxide, ozone, particulate sulphate, nitrates in aerosols and gaseous, nitric acid, ammonia and ammonium in aerosols	Monthly	Part 7.2
Precipitation chemistry (EMEP manual)	sulphate, nitrate, ammonium, chloride, sodium, potassium, calcium, magnesium and alkalinity	Monthly	Part 7.3
Throughfall	Sulphate, nitrate, ammonium, total N, chloride, sodium, potassium, calcium, magnesium, dissolved organic carbon and strong acid (by pH)	Weekly to monthly	Part 7.5
Soil chemistry	pH (CaCl2), S total, P total N total, Ca exchangeable, Mg exchangeable. K exchangeable, Na exchangeable, Al exchangeable, TOC, exchangeable titrable acidity (H+Al)	Every fifth year	Part 7.7
Soil water chemistry	pH, Electrical conductivity, Alkalinity, Gran plot, N total, ammonium, nitrate, P total, Ca, Mg, K, Na, Aluminium total, Aluminium labile	Four times annually	Part 7.8
Runoff water chemistry	alkalinity, sulphate, nitrate, chloride, dissolved organic carbon, pH, calcium, magnesium, sodium, potassium, inorganic (labile) aluminium, total nitrogen, ammonium, stream water runoff, specific conductivity	Monthly	Part 7.10
Foliage chemistry	Ca, K, Mg, Na, N, P, S, Cu, Fe, Mn, Zn and TOC	Every fifth year	Part 7.12
Litterfall chemistry	Ca, K, Mg, Na, N, P, S, Cu, Fe, Mn, Zn and TOC	Annually	Part 7.13
Vegetation (intensive plot)	Ground, field, shrub and tree layer vegetation, specifically soil-growing vascular plants, bryophytes and lichens. Tree diameter, canopy structure,	Three year	Part 7.17
Trunk epiphytes	Lichen species growing on living tree trunks	Every fifth year	Part 7.20
Aerial green algae	number of branches, youngest shoot with algae thickest coating of algae per tree, number of annual shoots with > 50 % needles left,, number of annual shoots with > 5 % nbeedles left	Annually	Part 7.21

4.   Relationship with other monitoring activities

Article 9 of the NEC-Directive requires that: ‘Member States shall coordinate with other monitoring programmes established pursuant to Union legislation including Directive 2008/50/EC, Directive 2000/60/EC, … and … Directive 92/43/EEC and, if appropriate, the LRTAP Convention and, where appropriate, make use of data collected under those programmes.’

The aim of these provisions is to maximise the use of data collected under existing systems to avoid duplication and exploit synergies. It is nonetheless important to identify the ecosystem types, sites and parameters concerned as set out under Section 3 above for the monitoring to be relevant for the purposes of the NEC-Directive.

4.1.    Relationship with the monitoring under EU legislation/initiatives

Extensive monitoring of freshwater bodies takes place under the Water Framework Directive (2000/60/EC), and monitoring of a wide range of habitats under the Habitats Directive (92/43/EEC). The information reported to the EU is available through the relevant Eionet databases (28) coordinated by the European Environment Agency.

Given the objective and site selection requirements for NEC-Directive monitoring, only a subset of sites under the Water Framework Directive are likely to be relevant for the current purposes. Mainly sites close to spring and surrounded by natural areas are of relevance for attributing water quality to air pollution impacts. A case study on the integration of monitoring under the Water Framework Directive into a monitoring network targeting air pollution impacts in Finland is provided in section 7.2.

Important other sources of data, which can be integrated into the Article 9 related monitoring, can be derived from LUCAS (Land use and land cover survey) (29) e.g. on soil carbon and nitrogen content. The EU Pollinators Initiative (30) as well as individual EU projects on monitoring ecosystems and biodiversity may provide additional opportunities for harmonisation, integration and increased efficiency of data collection across monitoring programmes.

4.2.    Relationship with monitoring under initiatives of the LRTAP Convention

The ecosystem monitoring activities under the Working Group on Effects (WGE) of the LRTAP Convention are directly relevant for the NEC-Directive implementation, having the same objectives and having developed substantial technical reference material in their more than 20 years of operation.

This long-term monitoring under the LRTAP Convention consequently provides substantial historical datasets monitored according to approved methodologies and therefore with consistent sampling and analysis procedures, and frequency.

The intensive WGE monitoring networks are ecosystem-based, issue-oriented (air pollution) and long-term. These characteristics allow the detection of ecosystem changes, assessment of contributing factors and identification of the consequences of ecosystem changes, thus informing policy makers about the state and predict future changes.

In summary, the objectives of ecosystem monitoring under the NEC-Directive are identical to those of the existing monitoring networks under the LRTAP Convention and so this monitoring should all be useful for NEC-Directive purposes as it:

—	Monitors indicators of acidification, eutrophication and ozone impacts in ecosystems (almost all parameters of Annex V);

—	Detects changes in the ecosystems;

—	Identifies the rate of change or trend (time scale), the extent of change (spatial scale) and the intensity of change (magnitude of the effect);

—	Allows for understanding of how the changes would affect the condition of the ecosystems;

—	Allows for the prediction and identification of those changes related to natural processes and human activities;

—	Facilitates modelling of the dynamics of ecosystems and related processes;

—	Enables the forecasting of potentially adverse effects and therefore provide ‘early warnings’;

—	Enables the evaluation of the effectiveness of policies.

It is also important to highlight that, within the LRTAP Convention, the issue-oriented monitoring combines both air pollution threats and effects monitoring in order to achieve a sufficient level of predictability, to better guide policy action. The simultaneous monitoring in trends of both ecosystem stress (air pollution) and ecosystem effects improves the interpretation of monitoring results.

4.3.    Relation with other monitoring networks

For monitoring ecosystem types that are not covered by ICPs, the LTER-Europe (Long Term Ecosystem Research Europe) network can be considered. LTER-Europe is a European umbrella organisation and research infrastructure for research sites and stations conducting environmental and ecosystem monitoring and research (31). One main aim is to organise all such European sites to build a knowledge base to improve the understanding of the structure and functions of ecosystems and their long-term response to environmental, societal and economic drivers.

The main objectives of LTER-Europe are:

—	to identify drivers of ecosystem change across European environmental and economic gradients;

—	to explore relations between these drivers, responses and developmental challenges under the framework of a common research agenda, and referring to harmonised parameters and methods;

—	to develop criteria for LTER sites and LTSER (32) platforms to support cutting edge science with a unique in-situ infrastructure;

—	to improve co-operation and synergy between different actors, interest groups, networks, etc.

LTER-Europe works towards these objectives by providing a framework for project development, conceptual work, education, exchange of know-how, communication and institutional integration. Some of the parameters useful for the Article 9 monitoring under the NEC-Directive are already monitored under LTER-Europe and Member States may want to explore whether and how the system could be complemented to cover further parameters (33).

Additionally, data from national forest inventories and other national monitoring activities can be used. Research projects can be another source of relevant data, such as remote sensing based information, which can provide spatially explicit information of the impacts of air pollution on plant condition (e.g. Cotrozzi et al. (2018) (34)).

5.   Reporting

5.1.    Reporting monitoring sites and indicators, as from 1 July 2018 and every four years thereafter

In reporting the location of the monitoring sites and the associated indicators used for monitoring air pollution impacts, in accordance with Article 10(4)(a) of the NEC-Directive, the following should be reported:

—	The coordinates and altitude of the site, name and habitat/ecosystem type and brief description of the site;

—	Details of which parameters are monitored at each site.

This information should be accompanied by an explanation setting out how the network was designed in view of the requirements set out in Article 9 of the NEC-Directive.

5.2.    Reporting data flows, as from 1 July 2019 and every four years thereafter

The reporting of monitoring data referred to in Article 9 of the NEC-Directive, in accordance with Article 10(4)(b), should reflect the following principles:

—	The reporting should be standardised following as far as possible existing data flows;

—	It should take into account INSPIRE-compliance (35);

—	It should build on the reporting schemes established under the ICPs.

On this basis, the Commission and the European Environment Agency have developed a template (36) for these reporting requirements, the use of which is highly recommended to allow for comparability and consistency of data and facilitate their analysis.

6.   Support for implementation

The exchanges of information on Member States' practice which informed the development of this guidance, were very useful. In this context the peer-to-peer tool established under the Commission's Environmental Implementation Review provides the possibility to organise further mutual support, whether in the form of twinning support mechanisms, or exchanges between larger groups of Member States on implementation and good practice. The tool uses the well-established Commission TAIEX instrument and, on the request of a Member State's public authority (national, regional, local, etc.), TAIEX can arrange missions of experts from public environmental authorities to provide expertise, study visits of staff to another Member State in order to learn from their peers, and single or multi-country workshops. More information, e-application and expert registration is available on the website:

http://ec.europa.eu/environment/eir/p2p/index_en.htm

Note also that the ICPs hold annual meetings which national experts can attend to learn more about monitoring and share experiences in running the sites. Information is available on the website:

https://www.unece.org/environmental-policy/conventions/envlrtapwelcome/meetings-and-events.html#/

7.   Case studies

7.1.    United Kingdom ozone monitoring

The UK has an intensive monitoring site for ozone run by the ICP Vegetation Programme Coordination Centre. At this site, hourly ozone concentrations and meteorology are monitored to enable calculation of cumulative stomatal ozone fluxes (POD) over the growing season for a variation of plant species (crops, trees, (semi-)natural vegetation). Hence, exceedance of flux-based critical levels of ozone can be calculated. In addition, foliar damage in ozone-sensitive species is monitored regularly, but not often observed due to the generally low ambient ozone concentrations at the site. The UK also has a rural network of ca. 20 monitoring sites where hourly ozone concentrations are recorded. When combined with modelled meteorological data, exceedances of flux-based critical levels of ozone can be calculated for these sites. Foliar ozone damage is currently not monitored at these sites.

7.2.    Integration of monitoring of Finnish surface waters under Water Framework Directive (WFD), ICPs under the LRTAP Convention and NEC-Directive

The Water Framework Directive (2000/60/EC) obliges Member States to carry out a surveillance monitoring programme to provide information e.g. for the assessments of long-term changes in natural conditions and long-term changes resulting from widespread (global) anthropogenic activity. To fulfil these surveillance objectives, monitoring of ecological status and chemical status for surface waters has to be carried out usually in water bodies that represent natural or semi-natural reference conditions and/or high/good ecological status. The monitoring of air pollution impacts of sulphur and nitrogen on aquatic ecosystems under the LRTAP Convention involves mainly the same objectives and surveillance designs, and therefore the monitoring of aquatic ecosystems under the ICPs of the LRTAP Convention is relevant to the WFD monitoring at reference sites (and vice versa). The aims and objectives of these monitoring programs are also relevant for the ecosystem monitoring under the NEC-Directive.

The WFD monitoring at reference sites in Finland – both chemical and biological – is primarily carried out in lakes and streams which are located in protected or remote area, or catchments are located in other areas with no or only minor direct human influence. Generally, these types of freshwaters in Finland are oligotrophic or dystrophic, the terrestrial catchment is mainly forested, and water chemistry is characterized by low or moderate ionic strength. These water bodies are therefore susceptible to air pollution impacts. To monitor the ecological status and chemical status of lakes and rivers under the WFD, the typology, which is representative of freshwaters, their natural and semi-natural habitats in Finland, consists of the following lake and river types (Table 8):

Table 8

Typology of Finnish freshwater bodies

(http://www.ymparisto.fi/en-US/Waters/State_of_the_surface_waters/Typology_of_surface_waters)

Lake types	River types
Small and medium-sized humus-poor lakes	Small peatland rivers
Small humic lakes	Small rivers in regions with mineral soils
Medium-sized humic lakes	Small rivers in regions with clay soils
Large humus-poor lakes	Medium-sized peatland rivers
Large humic lakes	Medium-sized rivers in regions with mineral soils
Humus-rich lakes	Medium-sized rivers in regions with clay soils
Shallow humus-poor lakes	Large peatland rivers
Shallow humic lakes	Large rivers in regions with mineral soils
Shallow humus-rich lakes	Large rivers in regions with clay soils
Lakes with very short water retention	Very large peatland rivers
Lakes in N. Lapland	Very large rivers in regions with mineral soils
Naturally nutrient-rich and calcium-rich lakes

Out of these 12 lake types for WFD monitoring, the types ‘small humus-poor’ or ‘small humic lakes’ (incl. shallow ones) involve small (A < 1 km2) forest headwater lakes, which are common in boreal regions in coniferous forest and peatland areas and are numerous in Finland, and have been shown to be sensitive to air pollution, as well as good indicators of air pollution impacts. The type ‘lakes in N. Lapland’ also includes sensitive lakes in forest or mountain areas in north Finland with low-ionic and nutrient-poor chemical characteristics. Correspondingly, the river types ‘small peatland rivers’ and ‘small rivers in regions with mineral soils’ include small streams in forest or mountain areas, and many of them are sensitive and good indicators of air pollutant impacts as well.

Monitoring of air pollution impacts on lakes and streams in forest and mountain reference areas in Finland are carried out under the LRTAP Convention (ICP Waters, ICP Integrated Monitoring) and national monitoring programmes. The regular monitoring started at most of the sites in 1990, and is presently being carried out at 34 sites covering geographically the whole country. To supplement WFD monitoring at reference sites, 18 out of the 34 ICP/national sites were integrated into WFD monitoring/reporting to provide information on long-term changes in natural conditions and long-term changes resulting from global pressures, mainly from atmospheric deposition and climate change. In return, the WFD monitoring provides biological data for requirements of assessments based on the LRTAP Convention. Assessments based on the LRTAP Convention and national monitoring programmes suitable for assessment of air pollution effects fulfil the demands of chemical analysis for the WFD, including pH, alkalinity, major anions and cations, nutrients and dissolved organic carbon. Monitoring targets, surveillance design (such as site establishment/selection, sampling and chemical analyses) and a common database are coordinated by the governmental Environmental Administration, including the Finnish Environment Institute and 13 Centres for Economic, Development, Transport and the Environment. The governmental Natural Resources Institute Finland (Luke) is also involved to national WFD monitoring, providing authority and expertise as regards fish monitoring. Centralised activities enable flexible risk-based and cost-effective approach in monitoring and reporting under different international programs, and in planning and implementation of new monitoring programs, such as monitoring under the NEC-Directive.

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(1)  Disclaimer: This guidance document is intended to assist national authorities in the application of Directive (EU) 2016/2284. It reflects the views of the European Commission and as such is not legally binding. The binding interpretation of EU legislation is the exclusive competence of the Court of Justice of the European Union (CJEU). The views expressed in this guidance document cannot prejudge the position that the Commission might take before the CJEU.

(2)  Directive (EU) 2016/2284 of the European Parliament and of the Council of 14 December 2016 on the reduction of national emissions of certain atmospheric pollutants, amending Directive 2003/35/EC and repealing Directive 2001/81/EC (OJ L 344, 17.12.2016, p. 1).

(3)  Directive 2001/81/EC of the European Parliament and of the Council of 23 October 2001 on national emission ceilings for certain atmospheric pollutants (OJ L 309, 27.11.2001, p. 22).

(4)  Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions - ‘A Clean Air Programme for Europe’, COM(2013) 918 final.

(5)  https://www.unece.org/env/lrtap/welcome.html

(6)  In full: ICP on Assessment and Monitoring Effects of Air Pollution on Rivers and Lakes; ICP on Assessment and Monitoring of Air Pollution Effects on Forests; ICP on Effects of Air Pollution on Natural Vegetation and Crops; ICP on Integrated Monitoring of Air Pollution Effects on Ecosystems.

(7)  Decision No 1386/2013/EU of the European Parliament and of the Council of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’ (OJ L 354, 28.12.2013, p. 171).

(8)  7th EAP point 28(d).

(9)  Directive 2009/147/EC of the European Parliament and of the Council of 30 November 2009 on the conservation of wild birds (OJ L 20, 26.1.2010, p. 7).

(10)  Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora (OJ L 206, 22.7.1992, p. 7).

(11)  Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (OJ L 327, 22.12.2000, p. 1).

(12)  See e.g. Annex 1 of the Habitats Directive 92/43/EEC.

(13)  Mapping and Assessment of Ecosystems and their Services – MAES: http://ec.europa.eu/environment/nature/knowledge/ecosystem_assessment/pdf/MAESWorkingPaper2013.pdf

(14)  European Nature Information System – EUNIS: https://www.eea.europa.eu/data-and-maps/data/eunis-habitat-classification

(15)  Corine Land Cover classes.

(16)  Metzger, M.J., Bunce, R.G.H, Jongman, R.H.G, Mücher, C.A., Watkins, J.W. 2005. A climatic stratification of the environment of Europe. Global Ecology and Biogeography 14: 549-563. DOI link: http://dx.doi.org/10.1111/j.1466-822x.2005.00190.x

(17)  See http://ec.europa.eu/environment/air/reduction/ecosysmonitoring.htm, especially http://ec.europa.eu/environment/air/pdf/Technical%20Specifications%20NEC%20Article%209%20location%20and%20indicators%20final.docx and http://ec.europa.eu/environment/air/pdf/template%20NEC%20Article%209%20location%20and%20indicators%20for%2001%20July%202018%20final.xlsx

(18)  Maes, J. et al., 2018, Analytical framework for mapping and assessing of ecosystem condition, http://ec.europa.eu/environment/nature/knowledge/ecosystem_assessment/pdf/Brochure%20MAES.pdf

(19)  ICP uses the term ‘plot’ instead of ‘site’.

(20)  UNECE ICP Forests Programme Co-ordinating Centre 2016. http://www.icp-forests.org/Manual.htm

(*1)  []: concentrations

(21)  Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe (OJ L 152, 11.6.2008, p. 1).

(22)  https://icpvegetation.ceh.ac.uk/publications/thematic; especially https://www.icpmapping.org/Latest_update_Mapping_Manual Chapter 3: Mapping critical levels for vegetation, LTRAP Convention, 2017

(1)  For a definition of ozone episode, see https://www.eea.europa.eu/themes/air/air-quality/resources/glossary/ozone-episode

(2)  Information on measurement height required.

(3)  If no measured data available, modelled hourly data could be used.

(4)  Information on latitude and altitude of site required as well as the biogeographical zone that the site is in (See Figure 1).

(5)  Measured hourly ozone concentrations and meteorology data are required for calculation of the stomatal ozone flux. Calculation of fluxes from estimated hourly ozone concentration data using passive samplers (accumulating ozone over a period of 1 – 2 weeks) is associated with high uncertainties.

(6)  https://www.sei-international.org/do3se

(23)  www.syke.fi/nature/icpim

(24)  Holmberg, M., Vuorenmaa, J., Posch, M., Forsius, M.,et al., 2013. Relationship between critical load exceedances and empirical impact indicators at Integrated Monitoring sites across Europe. Ecological Indicators 24, 256-265.

(25)  Dirnböck, T., Grandin, U., Bernhardt-Römermann, M., Beudert, B., Canullo, R., Forsius, M., Grabner, M.-T., Holmberg, M., Kleemola, S., Lundin, L., Mirtl, M., Neumann, M., Pompei, E., Salemaa, M., Starlinger, F., Staszewski, T., Uziębło, A.K., 2014. Forest floor vegetation response to nitrogen deposition in Europe. Global Change Biology 20, 429-440.

(26)  Vuorenmaa, J., Augustaitis, A., Beudert, B., Clarke, N., de Wit, H.A., Dirnböck, T., Frey, J., Forsius, M., Indriksone, I., Kleemola, S., 2017. Long-term sulphate and inorganic nitrogen mass balance budgets in European ICP Integrated Monitoring catchments (1990–2012). Ecological Indicators 76, 15-29.

(27)  UNECE ICP Integrated Monitoring Programme Manual 2017, http://www.syke.fi/en-US/Research__Development/Ecosystem_services/Monitoring/Integrated_Monitoring/Manual_for_Integrated_Monitoring

(28)  https://bd.eionet.europa.eu/activities/Reporting/Article_17, http://cdr.eionet.europa.eu/help/WFD/WFD_521_2016

(29)  https://ec.europa.eu/eurostat/statistics-explained/index.php/LUCAS_-_Land_use_and_land_cover_survey

(30)  http://ec.europa.eu/environment/nature/conservation/species/pollinators/index_en.htm

(31)  www.lter-europe.net

(32)  Long-Term Socio-Economic Research.

(33)  LTER sites and their measurement programmes can be found under https://data.lter-europe.net/deims/

(34)  Cotrozzi, L., Townsend, P. A., Pellegrini, E., Nali, C., Couture, J. J., 2018, Reflectance spectroscopy: a novel approach to better understand and monitor the impact of air pollution on Mediterranean plants. https://doi.org/10.1007/s11356-017-9568-2

(35)  https://inspire.ec.europa.eu/

(36)  http://ec.europa.eu/environment/air/reduction/ecosysmonitoring.htm