The Court of Justice of the European Union (“CJEU”) in Cases C-387/15 and C-388/15 Hilde Orleans and others v Vlaams Gewest (“Hilde Orleans”) provides some clarity on the appropriate assessment process under Directive 92/43/ EEC (the “Directive”).

The Hilde Orleans case involved a development of a large part of the port of Antwerp in Belgium pursuant to the Regional Development Implementation Plan ("RDIP") which, it was generally recognised, would adversely affect the integrity of the special area of conservation ("SAC") at the Scheldt and Durme estuary. In making a series of decisions in respect of the impact of the development, the Flemish authorities took into account new nature reserves which were to be established within ecological core areas within the SAC as part of the RDIP. A group of residents in the commune of Beveren challenged these decisions, resulting ultimately in a referral by the Belgian Council of State to the CJEU of the following questions:

i) Could the new nature reserves in ecological core areas be considered conservation or preventative measures that can be taken into account in carrying out the appropriate assessment, and

ii) Do the new nature reserves in the RDIP constiture "compensatory measures" under article 6(4) of the Directive?

Conservation and preventative measures

Article 6(1) of the Directive requires member states to protect SACs by establishing necessary conservation measures. Article 6(2) requires that member states take appropriate steps to avoid significant deterioration of habitats or disturbance of species in SACs. The Antwerp Port Authority and the Belgian Government had argued that the rules in the RDIP constituted conservation measures within the meaning of article 6(1) of the Directive (as the new nature reserves would be fully developed before any adverse effect could occur). The Belgian Government also argued, in the alternative, that the nature reserves amounted to preventative measures under article 6(2).

The CJEU noted that the provisions of article 6 of the Directive must be construed as a coherent whole in light of conservation objectives pursued by the Directive. Because the findings of fact made by the Belgian Court had shown that the measures (ie the new nature reserves) would result in the disappearance of a part of that site, such measures could not constitute conservation measures. Furthermore, a preventative measure could only comply with article 6(2) of the Directive where it was guaranteed not to cause any disturbance likely to significantly affect the objectives of the Directive, specifically the conservation objectives.

Mitigation measures and the Briels case

Having decided that the new nature reserves could not amount to conservation or preventative measures, the CJEU then considered the extent to which the reserves could be classified as a mitigation measure under article 6(3) of the Directive. The latter provision requires an appropriate assessment to be undertaken where a plan or project is "likely to have significant effect" on an SAC, and that national authorities only grant consent for the plan or project where it does not adversely affect the integrity of the site.

Referring to its earlier decision in Case C-521/12 Briels and others, the CJEU noted that the circumstances in this case were similar to those pertaining in the Briels case insofar as they involved, at the time of assessing the implications of the plan or project for the site concerned, the identical premise that future measures may mitigate the significant adverse effects on that site, even though the development measures in question have not been completed. The Briels case involved a Dutch motorway widening project which affected the protection of molinia habitats within a SAC. The CJEU in that case was asked to consider whether the creation of a new habitat within the SAC equivalent to that lost as a result fo that project amounted to a mitigation measure under article 6(3) of the Directive or a compensatory measure under article 6(4). Crucially, the measures envisaged in the Briels case were to be completed subsequent to the adverse effects on the integrity of the SAC, unlike the Hilde Orleans case where the habitat creation measure was proposed to be created before the original habitat was lost. The CJEU in Briels held that the creation of a new habitat was not a mitigation measure, and held that creating a habitat to replace a lost one as part of a project can never amount to mitigation, and accordingly, cannot be taken into account when assessing the effect on the integrity of the site during the appropriate assessment.

Discussing article 6(3), the CJEU in Hilde Orleans emphasised that the appropriate assesment must contain complete, precise and definitive conclusions capable of removing all reasonable scientific doubt as to the effects of the works proposed on the protected site concerned. Any positive effects of a future creation of a new habitat in the SAC are highly difficult to forecast with any degree of certainty and would be visible only several years into the future. In this case, the CJEY held that the adverse effects on the SAC site from the RDIP were certain, but the benefits from the creation of new nature reserves were uncertain. Citing the Briels case, the CJEU warned that mitigation measures (which are in reality compensatory measures) could not be used to circumvent the provisions of article 6(3) of the Directive and to authorise projects which adversely affect the integrity of the site concerned.


Finally, the CJEU considered the provisions of article 6(4) of the Directive, which allows for plans or projects that adversely affect the integrity of the SAC to proceed only for imperative reasons of overriding public interest ("IROPI"). IROPI include situations where the is no alternative solution or where the are reasons for a social or economic nature of the project to proceed. However, these reasons will only be considered in circumstances where appropriate compensatory measures are taken.

The CJEU repeated that the provisions of article 6(4) must be interpreted strictly. In order to determine the nature of any compensatory measures, the damage to the site concerned must be precisely defined. The assessment of IROPI and of the existence of less harmful alternatives require a weighing up against the damage caused to the site by the plan or project under consideration. The CJEU confirmed that the measures at issue in the Hilde Orleans case could be considered "compensatory measures" under article 6(4), provided that the conditions of that provision are satisfied.

Concluding remarks

The Hilde Orleans case, along with the Briels case, provides useful guidance to national authorities carrying out appropriate assessments of a plan or project under article 6(3) and the consideration of compensatory measures under article 6(4). In particular, it is imperative that, where a plan or project proposes to create a new, replacement habitat after the appropriate habitat has been carried out, no account should be taken of that proposal as part of the article 6(3) assessment.