1. 

A road-widening project in the Netherlands affects a special area of conservation within the meaning of the Habitats Directive. ( 2 ) It is likely in particular to reduce the area and/or quality of molinia meadows ( 3 ) within that area. Certain measures have been ordered with a view to ensuring the creation of new meadows elsewhere in the same site, to replace or augment those affected. Legal challenges have been brought against the ministerial orders approving the project subject to those measures.

2. 

In that context, the Raad van State (Council of State) wishes to know, essentially, whether the integrity of a site is adversely affected within the meaning of the Habitats Directive if the project includes the creation of an area of that natural habitat type of equal or greater size within that site; and, if so, whether that creation is to be regarded as a ‘compensatory measure’ within the meaning of the same directive.

3.

Article 1 of the Habitats Directive contains a number of definitions, in particular:

…

…

…

…’

4.

Article 2 provides:

‘1.   The aim of this Directive shall be to contribute towards ensuring bio-diversity through the conservation of natural habitats and of wild fauna and flora in the European territory of the Member States to which the Treaty applies.

2.   Measures taken pursuant to this Directive shall be designed to maintain or restore, at favourable conservation status, natural habitats and species of wild fauna and flora of Community interest.

3.   Measures taken pursuant to this Directive shall take account of economic, social and cultural requirements and regional and local characteristics.’

5.

Article 3(1) provides:

‘A coherent European ecological network of special areas of conservation shall be set up under the title Natura 2000. This network, composed of sites hosting the natural habitat types listed in Annex I and habitats of the species listed in Annex II, shall enable the natural habitat types and the species’ habitats concerned to be maintained or, where appropriate, restored at a favourable conservation status in their natural range.

…’

6.

Article 6 of the Habitats Directive reads as follows:

‘1.   For special areas of conservation, Member States shall establish the necessary conservation measures involving, if need be, appropriate management plans specifically designed for the sites or integrated into other development plans, and appropriate statutory, administrative or contractual measures which correspond to the ecological requirements of the natural habitat types in Annex I and the species in Annex II present on the sites.

2.   Member States shall take appropriate steps to avoid, in the special areas of conservation, the deterioration of natural habitats and the habitats of species as well as disturbance of the species for which the areas have been designated, in so far as such disturbance could be significant in relation to the objectives of this Directive.

3.   Any plan or project not directly connected with or necessary to the management of the site but likely to have a significant effect thereon, either individually or in combination with other plans or projects, shall be subject to appropriate assessment of its implications for the site in view of the site’s conservation objectives. In the light of the conclusions of the assessment of the implications for the site and subject to the provisions of paragraph 4, the competent national authorities shall agree to the plan or project only after having ascertained that it will not adversely affect the integrity of the site concerned and, if appropriate, after having obtained the opinion of the general public.

4.   If, in spite of a negative assessment of the implications for the site and in the absence of alternative solutions, a plan or project must nevertheless be carried out for imperative reasons of overriding public interest, including those of a social or economic nature, the Member State shall take all compensatory measures necessary to ensure that the overall coherence of Natura 2000 is protected. It shall inform the Commission of the compensatory measures adopted.

Where the site concerned hosts a priority natural habitat type and/or a priority species, the only considerations which may be raised are those relating to human health or public safety, to beneficial consequences of primary importance for the environment or, further to an opinion from the Commission, to other imperative reasons of overriding public interest.’

7.

Finally, the list of habitat types in Annex I to the Habitats Directive includes, among semi-natural tall-herb humid meadows, ‘6410 Molinia meadows on calcareous, peaty or clayey-silt-laden soils (Molinion caeruleae)’. It is not a priority habitat.

8.

The Commission has published a guidance document (2007/2012; ‘the guidance document’) on Article 6(4) of the Habitats Directive, point 1.4.1 of which states, inter alia, that, in the context of Article 6 of the Habitats Directive, mitigation measures must be clearly distinguished from compensatory measures. Although ‘compensatory measures’ are not defined in the directive, according to the guidance document experience suggests that:

9.

The guidance document goes on to state that compensatory measures should be additional to those which are normal practice under the Habitats Directive or required by law, such as the implementation of a management plan; they should go beyond the normal or standard measures required for the protection and management of Natura 2000 sites. ‘Consequently, compensatory measures are not a means to allow the implementation of plans or projects while escaping the obligations of Article 6. They should be considered only after having ascertained a negative impact on the integrity of a Natura 2000 site.’ Only once it is decided that the project or plan should proceed is it appropriate to move to a consideration of compensatory measures; they are the ‘last resort’, when the other safeguards provided for by the directive are ineffectual and the decision has been taken to consider, nevertheless, a project or plan having a negative effect on the Natura 2000 site.

10.

The Commission has also published ‘Methodological guidance on the provisions of Article 6(3) and (4) of the Habitats Directive’ (November 2001; ‘the methodological guidance’), in which it sets out its views on the approach to be taken under those provisions. It lists four consecutive stages: first, screening; second, appropriate assessment (which takes conservation objectives into account and includes assessment of mitigation measures); third, assessment of alternative solutions; fourth, assessment where no alternative solutions exist and where adverse impacts remain (which includes identification and assessment of compensatory measures).

11.

The Court has considered Article 6 of the Habitats Directive on a number of occasions. Most recently, it has summarised its case-law in Sweetman. ( 4 ) It may be helpful to set out here the relevant paragraphs of that judgment:

…

…

…

12.

It may also be helpful to bear in mind some guidance provided by, in particular, Advocate General Kokott, who stated, at point 17 of her Opinion in Commission v Netherlands: ( 7 )‘… alternatives do exist which do not alter plans or projects in the sense of providing alternative plans or projects, but merely concern the way in which they are carried out. [For example,] activities causing disturbance could be carried out in periods when the disturbance is at its lowest. Such alternative methods of carrying out plans or projects can be among the aspects of a plan or project already requiring examination in the context of an assessment under Article 6(3) of the Habitats Directive. The competent authorities are required to have regard to the results of such an assessment for the purposes of the second sentence of Article 6(3) when making authorisation decisions, even when the integrity of the site is not adversely affected. Appropriate obligations can … contribute to the maintenance, at a favourable conservation status, of natural habitats and species of wild fauna and flora of Community interest. Article 6(4) does not, however, apply to these alternative methods of carrying out plans and projects, but rather to alternative plans and projects.’

13.

Then, at point 35 of her Opinion in Commission v Portugal, ( 8 ) Advocate General Kokott stated: ‘Within the framework of Article 6 of the Habitats Directive, the adverse effects on a site must be strictly separated from the compensatory measures. Under the regulatory system of the Habitats Directive, adverse effects are to be avoided as far as possible. That is done preferably by eliminating any risk of harm or by taking appropriate damage mitigation and prevention measures. By contrast, compensatory measures can be considered only when adverse effects have to be accepted in the absence of any alternative, for overriding reasons of public interest. The preservation of existing natural resources is preferable to compensatory measures simply because the success of such measures can rarely be predicted with certainty.’

14.

The referring court gives the following account of the facts and argument in the case before it.

15.

On 6 June 2011 the Minister van Infrastructuur en Milieu (Minister for Infrastructure and the Environment, ‘the Minister’) adopted an order concerning the widening of the A2 motorway, amended by further order of 25 January 2012 (together, ‘the motorway order’). A number of parties have challenged those orders, but most of the grounds advanced have been dismissed. However, the referring court has not yet reached a decision on a ground concerning the effects of the road-widening on the Natura 2000 site Vlijmens Ven, Moerputten and Bossche Broek (‘the Natura 2000 site’), which is a special area of conservation for, in particular, the natural habitat type molinia meadows. ( 9 ) The conservation objectives for the site are expansion of the area and improvement in quality.

16.

A preliminary environmental impact assessment report found that serious adverse effects from nitrogen deposits could not be ruled out. A second report stated that, in Moerputten, a temporary increase in nitrogen deposits would lead to slight acceleration of the decrease in quality already occurring. In Bossche Broek, the quality of the molinia meadows was high but potentially in danger. Adverse effects from increased nitrogen deposits could not be ruled out. Furthermore, although the molinia meadows could spread out over several decades, there would still be an increase in nitrogen deposits in 2020, and the spread might be restricted. In Vlijmens Ven, molinia meadows could develop rapidly after the hydrological system was completed, and the temporary increase in nitrogen deposits would not cause adverse effects. The report concluded that mitigating measures should be adopted to remove the adverse effects of the road-widening.

17.

Article 6(2) of the motorway order stated that the hydrological situation in Vlijmens Ven was to be improved as a mitigating measure to counter possible adverse effects on the molinia meadows, allowing expansion of that natural habitat type inside the site. The mitigation plan anticipated redevelopment of Vlijmens Ven beginning in 2012, with new molinia meadows first appearing in 2013. The new meadows in Vlijmens Ven would to a large extent offset the consequences of the increase in nitrogen deposits for the existing 11.5 hectares of molinia meadows in the Natura 2000 site as a result of traffic on the widened A2.

18.

Several parties in the main proceedings submit that the proposed creation of new molinia meadows in the Natura 2000 site should not have been taken into account when considering whether the integrity of the site was adversely affected, and that the Minister is wrong to view the creation of new molinia meadows as a mitigating measure.

19.

The Minister argues that there can be no question of the site having been adversely affected because the conservation objectives for this natural habitat type are sufficiently met by the planting of new molinia meadows as stipulated in the motorway order.

20.

The referring court finds it necessary to establish whether the Minister could lawfully take the position that the integrity of the Natura 2000 site would not be adversely affected.

21.

The road-widening as such has adverse effects on the existing area of molinia meadows. However, the motorway order sets out a mitigation plan aimed at creating a larger area of molinia meadows, of higher quality than at present. The Minister’s position assumes that, where a project could adversely affect an area of protected natural habitat in a Natura 2000 site, the assessment of whether the integrity of the site is affected should take account of the creation of an equivalent or larger area of that natural habitat type within the same site, which will not be adversely affected.

22.

The referring court considers that neither the wording of the Habitats Directive nor the case-law of the Court indicates how to assess whether the integrity of the site is affected for the purposes of Article 6(3). It therefore seeks a preliminary ruling on the following questions:

‘1.   Is the expression “will not adversely affect the integrity of the site” in Article 6(3) of [the Habitats Directive] to be interpreted in such a way that, where the project affects the area of a protected natural habitat type within the site, the integrity of the site is not adversely affected if in the framework of the project an area of that natural habitat type of equal or greater size is created within that site?

2.   If the answer to the first question is that the expression “will not adversely affect the integrity of the site” is to be interpreted in such a way that [in the circumstances set out in the first question] the integrity of the Natura 2000 site is adversely affected, is the creation of a new area of a natural habitat type then to be regarded in that case as a compensatory measure within the meaning of Article 6(4) of the directive?’

23.

When the order for reference was received in the present case, the procedure in Sweetman was too far advanced for the two to be joined. The present case was therefore suspended, allowing interested parties to submit their observations following the judgment in Sweetman.

24.

Written observations have been submitted by one of the applicants in the main proceedings (Stichting Overlast A2 Vught en omstreken, ‘the Stichting’), by the Kingdom of the Netherlands, by the United Kingdom and by the European Commission, all of whom also presented oral argument at the hearing on 11 December 2013, which concentrated in particular on the concepts of ‘mitigation measures’ in the Commission’s guidance and ‘compensatory measures’ in the Habitats Directive.

25.

With regard to the facts of the case in the main proceedings, both the Stichting and the Commission have pointed out the existence of a LIFE+ project, ( 10 ) independent of the motorway-widening project, with the key specific goal of enlarging and improving areas of, in particular, molinia meadows within the Natura 2000 site as habitat for two species of butterfly. The project, entitled ‘Blues in the Marshes’, ( 11 ) includes ‘170 ha of newly naturalised grassland habitats’ in the larger part of the site (Vlijmens Ven and Moerputten). It received part-funding from the European Union in June 2012 and is planned to be carried out between then and December 2018.

26.

The referring court asks two questions, which amount to the following. Where the existing area of a protected natural habitat type within a Natura 2000 site is affected by a project which is none the less conditional on the creation of a new (equal or greater) area of the same natural habitat type elsewhere within the same site, is the integrity of the site itself adversely affected within the meaning of Article 6(3) of the Habitats Directive? If so, is the creation of the new area to be regarded as a compensatory measure within the meaning of Article 6(4) of the same directive?

27.

The interrelationship between those questions – which, in my view, should both be answered in the affirmative – is such that it seems useful to consider them together.

28.

In that regard, a brief analysis of Article 6 of the Habitats Directive might provide a preliminary answer. Compensatory measures are required by Article 6(4) where (i) there has been a negative assessment under Article 6(3), (ii) there are no alternative solutions and (iii) the plan or project must go ahead for imperative reasons of overriding public interest. Thus, it is clear from the structure of the two paragraphs, read together, that such measures are not contemplated in the context of Article 6(3). Logically and chronologically, they follow a negative assessment under that provision. If compensatory measures as envisaged in Article 6(4) were taken into account in the context of the assessment under Article 6(3), either (a) they would be insufficient to prevent an adverse effect, in which case the plan or project could not go ahead at all, or (b) they – and the plan or project – would be adopted without any requirement to consider first whether there were alternative solutions or imperative reasons of overriding public interest for proceeding. In either event, Article 6(4) would be ineffective. Such an approach would fail to construe Article 6 – in which paragraph 4 is clearly intended to be effective – as a coherent whole, as required by the case-law. ( 12 )

29.

However, it is advisable to go further than that rather formal analysis and look at the substance of the provisions. Before doing so, it is helpful to consider the term ‘mitigation measure’ which, although not used in the legislation or defined in the case-law, has been widely debated before the Court in the present case.

30.

It is generally agreed among environmental specialists, and it appeared to be common ground among those presenting argument at the hearing, that plans or projects likely to have an effect on the environment should be assessed in the light of a ‘mitigation hierarchy’. The content of that hierarchy may be expressed in greater or lesser detail and in slightly varying forms but its essence may be stated thus: ‘compensation for residual harm is a last step and comes after consideration of how harm can be avoided in the first place and then, if that is not possible, how harm can be minimised through mitigation’. ( 13 ) The three major steps or levels are thus, in decreasing order of preference: avoid, mitigate, compensate. ( 14 )

31.

A comparable hierarchy can be seen in Article 6 of the Habitats Directive, although there is no mention of mitigation as such. Article 6(1) requires the establishment of conservation measures, namely, in accordance with Articles 1(a), 2(2) and 3(1), those measures necessary ‘to maintain or restore’ the natural habitats ‘at a favourable status’. That level is thus rather higher than simple avoidance, in that it involves active maintenance or even improvement of the quality or extent of habitats. Next, Article 6(2) requires the taking of appropriate steps to avoid any deterioration or disturbance. With a view to ensuring the same level of protection, ( 15 ) Article 6(3) allows plans or projects to be approved only if they ‘will not adversely affect the integrity of the site concerned’. Finally, Article 6(4) requires all necessary compensatory measures to be taken whenever a plan or project, even though it does adversely affect the integrity of the site, must be carried out for imperative reasons of overriding public interest and there are no alternative solutions.

32.

Thus, although Article 6 of the Habitats Directive does not specifically mention mitigation measures, it cannot reasonably be argued that there is no place for them within its structure. I agree with all those who have submitted observations, and with Advocate General Kokott in the passages I have cited above, that measures which form part of a plan or project and which effectively minimise its impact may be taken into account when assessing, in accordance with Article 6(3), whether that plan or project adversely affects the integrity of a site. It seems clear, however, that Article 6(1) requires active conservation management, rather than a mere absence of negative impact, and that Article 6(4) concerns situations in which whatever measures can be implemented in order to reduce an adverse impact have proved insufficient in the context of the assessment under Article 6(3).

33.

All those who have submitted observations agree, therefore, that ‘mitigation measure’ designates a relevant concept for the purposes of Article 6(3) of the Habitats Directive, which is different from that of ‘compensation measure’ in Article 6(4). In addition, the place of Article 6(3) in the structure of Article 6 as a whole corresponds to the place of ‘mitigation’ or ‘minimisation’ in the mitigation hierarchy as generally accepted.

34.

I turn now to the questions raised by the national court. The issue as debated before the Court is essentially whether a measure of the kind in issue in the main proceedings is a mitigation measure which (it is agreed) may be taken into account in the context of Article 6(3), or a compensatory measure; and, if the latter, whether it may still be taken into account in the context of Article 6(3) or only in that of Article 6(4). It has not been claimed that such measures cannot qualify even as compensatory measures, but it has been argued that the specific measures in issue in the main proceedings should be disregarded in the assessment of the effects of the motorway-widening project if they are in reality ordinary measures of management of the Natura 2000 site.

35.

In the first place, therefore, two dividing lines must be drawn: between mitigation measures and compensation measures, and between measures which may be taken into account in the context of Article 6(3) of the Habitats Directive and those which can be taken into account only in the context of Article 6(4). It is not possible to assert, a priori, that those two dividing lines are identical. ( 16 )

36.

The basic semantic distinction between mitigation (or minimisation or reduction) and compensation (or offsetting) does not appear to me to be very controversial. In the context of Article 6(3) and (4) of the Habitats Directive, a mitigation measure must be one which lessens the negative effects of a plan or project, with the aim of ensuring, if possible, that (while some insignificant and/or transient effects might not be totally eliminated) the ‘integrity of the site’ as such is not adversely affected. A compensatory measure, by contrast, is one which does not achieve that goal within the narrower framework of the plan or project itself but seeks to counterbalance the failure to do so through different, positive effects with a view to, at the very least, avoiding a net negative effect (and, if possible, achieving a net positive effect) within a wider framework of some description. ( 17 )

37.

In that light, I would classify the measures in issue in the main proceedings as being, in principle, compensatory measures. From their description, it appears to be accepted that the quality and/or extent of (some of) the existing molinia meadows in the Natura 2000 site may deteriorate as a result of the widening of the motorway. It seems that those meadows are at risk of deterioration through (long-term) increased nitrogen deposits due to increased motorway traffic and that, while no steps taken or planned are such as to provide an adequate reduction of that pollution or to prevent it from reaching the areas of molinia meadow nearest the motorway, new meadows are planned and are expected to lie beyond the reach of the increased pollution.

38.

I cannot, therefore, agree with the Netherlands Government that the creation of new molinia meadows elsewhere within the Natura 2000 site is a mitigation measure; it is a compensatory measure.

39.

However, that conclusion does not of itself mean that such a measure cannot be taken into account in the context of Article 6(3) of the Habitats Directive. That provision makes no mention of either mitigation or compensatory measures but concentrates on the result to be achieved – no adverse effect on the ‘integrity of the site’.

40.

In the view of the Netherlands and United Kingdom Governments, the ‘integrity of the site’ must be considered as a whole, in terms of net loss or benefit: it does not matter that a particular habitat is lost in one part of the site, provided that at least an equivalent (and, preferably, a greater) area and quality of the same habitat is created elsewhere within the site. Thus, particularly in the submission of the United Kingdom, a compensatory measure of that kind may be taken into account in the context of Article 6(3) of the Habitats Directive.

41.

I can agree that the ‘integrity of the site’ should be viewed as a whole in the sense that it is its enduring essential character which must be considered, rather than insignificant and transient fluctuations in quality or area of a particular habitat. However, it seems to me that long-term deterioration of an existing natural habitat is something which necessarily concerns enduring essential character rather than insignificant and transient fluctuations. The same must apply where there is (or is likely to be) acceleration of an existing decrease in quality or a limitation of a possible increase in area (both of which are predicted in parts of the Natura 2000 site in the present case). In all cases, Article 6(3) requires the assessment to be made ‘in view of the site’s conservation objectives’ – which, in the present case, are expansion of the area of molinia meadow and improvement of its quality. Where deterioration of the kinds described cannot be ruled out, it must in my view be concluded that the integrity of the site, viewed in the light of its conservation objectives, is adversely affected.

42.

The fact that new areas of habitat may be created elsewhere in the same site does not appear to me to be relevant in that regard, even if a net beneficial effect is predicted. There is still an adverse – possibly even irreparable – effect on the existing natural habitat, and thus on the integrity of the site. The new habitat will be, to some extent, artificially created and cannot become a true natural habitat for some, possibly quite considerable, time. Indeed, as was pointed out by counsel for the Stichting at the hearing, there can be no certainty that steps to create a new area of a particular habitat will in fact ever achieve the desired outcome and, in application of the precautionary principle, absence of uncertainty is a condition for approval in the context of Article 6(3) of the Habitats Directive. ( 18 ) Outcomes cannot be guaranteed in heavily-managed agriculture; it is all the more difficult to guarantee them when seeking to encourage nature to take its course. The Court has stated that there must be no remaining scientific doubt before it can be concluded that there are no lasting adverse effects on the integrity of a site. The same standard must in my view be applied to predictions of success for planned new areas of created ‘natural’ habitat.

43.

I am not swayed by the United Kingdom’s argument that the approach I advocate here might lead to the ‘absurd’ result that a plan which had an adverse effect on a habitat could be approved in accordance with Article 6(3) of the Habitats Directive because that effect was too insignificant to constitute an adverse effect on the integrity of the site, whereas another plan which involved deterioration of a limited area of habitat and its replacement by a larger area of the same habitat, with a net overall benefit, could not be so approved. On the one hand, as I have said, there can be no guarantee of success for the new habitat or, thus, of the net benefit, so that the United Kingdom’s position might not be consistent with the precautionary principle. On the other hand, the fact that approval is not possible in accordance with Article 6(3) does not in itself preclude approval in accordance with Article 6(4), whose wording specifically takes account of compensatory measures.

44.

Nor am I swayed by the Netherlands Government’s argument that, while a project such as the widening of the A2 motorway can no doubt meet the standard of ‘imperative reasons of overriding public interest’ and therefore qualify for approval in accordance with Article 6(4) of the Habitats Directive by virtue of the compensatory measures implemented, that would be unlikely to be the case for a private project (for example, an extension of a pig farm) even if it included the same or even more effective compensatory measures and thus led to the same or an even greater net benefit. It is clear that, in Article 6(3) and (4), the legislature laid down different criteria. Under Article 6(3), any project may qualify for approval, provided that it does not adversely affect the integrity of the site. Under Article 6(4), a project which does not qualify for approval under Article 6(3) may none the less be approved, provided that, inter alia, it must be carried out for imperative reasons of overriding public interest. The fact that many, if not most, private projects will not meet that criterion does not justify reclassifying a measure which does not minimise an adverse effect on the integrity of the site as one which does.

45.

At this point, it is necessary to address also a further argument put forward by the Member States present at the hearing, namely that, because Article 6(4) of the Habitats Directive requires the taking of ‘all compensatory measures necessary to ensure that the overall coherence of Natura 2000 is protected’ (emphasis added), that provision concerns only measures which are taken outside the particular site adversely affected by the plan or project.

46.

I can agree that it is clear from the wording of Article 6(4) that the compensatory measures referred to need not be within the affected site but may concern other sites within the Natura 2000 network. ( 19 ) That does not however mean, in my view, that they are explicitly limited to such other sites. A compensatory measure differs from a measure of mitigation, minimisation or reduction by its nature, not by its geographical location. Although an adverse effect on the integrity of one site is unlikely to be mitigated by measures taken in another site, that logic does not apply where compensation is concerned. A compensatory measure is, by its nature, separate from that for which it seeks to compensate, whereas a mitigation measure is of necessity bound up with that which it is designed to mitigate. However, the fact that compensatory measures may be implemented elsewhere than in the affected site does not mean that they cannot be implemented within (possibly in another part of) that site. Nor is a measure any less likely to protect the overall coherence of Natura 2000 where it is implemented within the affected site than where it is implemented in another part of the Natura 2000 network (if anything, it may be more likely to do so). And I find nothing in the wording of Article 6(4) of the Habitats Directive to persuade me otherwise.

47.

Another relevant point which has been raised, but which concerns issues of fact which can be determined only by the competent national court, is the relationship between the creation of new areas of molinia meadow as a condition for the implementation of the motorway-widening project and the creation of such areas in the context of the LIFE+ project I have referred to at point 25 above. The Stichting and the Commission have suggested, if I understood their submissions correctly, that the condition in Article 6(2) of the motorway order may not in fact have represented a new requirement to which implementation of the project was made subject but rather that the aim was in effect to rely on the beneficial effects of the LIFE+ project to counterbalance the detrimental effects of the motorway-widening project.

48.

It seems to me that, if that were found to be the case, it would not be possible to regard the measures in issue in the main proceedings as compensatory measures for the purposes of Article 6(4) of the Habitats Directive. The LIFE+ project in question appears to fall within the scope of the conservation measures and management plans required by Article 6(1) of that directive. Article 6(3) concerns only plans or projects ‘not directly connected with or necessary to the management of the site’ and requires them to be assessed ‘in view of the site’s conservation objectives’. I interpret that to mean that those objectives and that management are to be considered to form part of the ‘integrity of the site’ against which the effects of the plan or project are to be assessed. They cannot serve at the same time as (a mitigating element in) part of the plan or project itself. The same must be true a fortiori when a plan or project already assessed in the context of Article 6(3) comes under further examination in the context of Article 6(4).

49.

My view is therefore that measures of the kind described in the order for reference are not relevant to the assessment as to whether, for the purposes of Article 6(3) of the Habitats Directive, a plan or project adversely affects the integrity of the site, but that they may be taken into account for the purposes of Article 6(4), provided that they are specific to the plan or project and not part of a management or conservation plan to be carried out in any event. Consequently, it is not strictly necessary to consider what requirements would need to be met for a different type of measure to be taken into account in the context of Article 6(3). Nevertheless, it may be helpful to set out briefly the core of those requirements, particularly with regard to two aspects which have perhaps not yet been set out specifically in the Court’s judgments. Here, I am largely in agreement with the criteria put forward at the hearing by the Member States present.

50.

On the one hand, not only is a mitigation measure necessarily bound up with the effect which it is intended to mitigate – so that it must concern the same site and the same habitat type – but it must, in order to be considered in the context of Article 6(3), form an integral part of the plan or project under consideration. It may, as the United Kingdom submitted, be included in the original plan or project or be inserted as a condition at a later stage (but before approval of the plan or project), to deal with predicted effects. The mere fact that a measure is likely to mitigate the effects of a plan or project is not, however, enough: it must be specific to that plan or project and not part of any independent framework.

51.

On the other hand, as a corollary to the above, the measures must form a legally binding condition for the implementation of the plan or project if it is to be given approval. They must also (as, so to speak, the other side of the same coin) not be required if the plan or project does not receive approval. That does not mean that they may not be carried out unless the plan or project is approved (because they might, of course, serve some separate, useful purpose) but only that they cannot be regarded as specifically included in the plan or project if they are in fact the subject of some independent legal requirement.

52.

In the light of all the foregoing considerations, I am of the opinion that the Court should answer the questions raised by the Raad van State to the following effect: