Hilde Orleans and others v Vlaams Gewest (joined cases C-387/15 and C-388/15), decided by the European Court of Justice on 21 July 2016. We discuss how the ECJ’s decision in this case concerning appropriate assessment under the Habitats Directive 1992, follows on from and clarifies existing case law in this area. 


Article 6 of the Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora, or the “Habitats Directive”, contains provisions that aim to protect Special Areas of Conservation (“SACs”), which have been designated under the Habitats Directive to protect threatened habitats and species.

  1. Article 6(1) requires member states to protect SACs by establishing “necessary conservation measures”.
  2. Article 6(3) provides that, where a plan or project that is not directly connected with or necessary to the management of a SAC is likely to have a “significant effect” on that SAC, an “appropriate assessment” of the implications for the SAC must be undertaken. The competent national authority may only grant consent for the plan or project if it will not “adversely affect the integrity of the site”.
  3. Article 6(4) provides that, where an appropriate assessment results in a “negative assessment” of the implications for the site,a plan or project may nevertheless be carried out where there is no alternative solution, and if it is for "imperative reasons of overriding public interest" (“IROPI”), including those of a social or economic nature. However, compensatory measures must be adopted.


The Orleans case follows on from the landmark case of Briels v Minister van Infrastructuur en Milieu (C-521/12), which dealt with a similar point.

The case of Briels concerned a Dutch motorway widening project, which affected land within a SAC, designated for the protection of a certain habitat – molinia meadows. As part of the project, an area of molinia habitat within the SAC would be lost and it was proposed that new molinia meadows would be created elsewhere within the SAC.

The question before the ECJ was whether the creation of the new habitat within the SAC, which would be equivalent to that lost as a result of the project, could be regarded as a mitigation measure, which would avoid an “adverse affect” on the integrity of the SAC within the meaning of Article 6(3) of the Habitats Directive; or whether it was in fact a “compensatory measure” within the meaning of Article6(4) of the Habitats Directive.

The Court rejected arguments that the habitat creation could be viewed as “mitigation” because it was a planned part of the project and would fall within the SAC. A key aspect of the Court’s reasoning was that, where it was proposed as part of a project that habitat be created to replace habitat being lost from a SAC as the result of the same project, this could never be viewed as a “mitigation” measure. The measure instead had to be categorised as “compensatory”(assuming it met the relevant criteria).

The result of this was that the habitat creation measure could not betaken into account when assessing the affect on site integrity at appropriate assessment stage. On that basis, it was found that the project would be liable to adversely affect the integrity of the SAC within the meaning of Article 6(3).


While it clarified the law to some extent on “mitigation” vs. “compensation” measures, Briels did not touch on the question of whether a proposal, as part of a project, to create new habitat to replace habitat being lost as a result of the same project, could be viewed as “compensation” where the new habitat proposed would be created before the original habitat was lost, thereby potentially avoiding any adverse effects on the protected area. Orleans considered just that point.

The case concerned the development of a large part of the port of Antwerp in Belgium. The project would lead to the loss of land within a SAC known as the ‘Scheldt and Durme estuary from the Dutch border to Ghent’,designated as being a SAC in particular for the habitat type ‘estuary’.

The project would include a mandatory requirement for nature reserves to be created in ecological core areas within the SAC, identified in the project development plan. The Flemish authorities proceeded in their decision-making between 2012 and 2014 on the basis that the creation of the nature reserves would constitute “conservation measures”, under Article 6(1) of the Habitats Directive, rather than compensatory measures, under Article 6(4). This was because, it argued, the nature reserves would be fully developed before any adverse affect on the SAC could occur, due to the timing of the works. The authorities thus argued that the nature reserves could be taken into account when carrying out an appropriate assessment of the project under Article 6(3).

These decisions were challenged by a group of residents of the commune of Beveren, which is one of the areas affected by the project.

The national court Raad van State (Council of State) stayed the proceedings and referred the case to the ECJ.


On 21 July 2016, the ECJ decided that the creation of the new nature reserves could not amount to conservation measures under Article 6(1), or preventive measures under Article 6(2), since the project would result in the loss of part of the SAC. The question then arose as to whether the proposal could be classified as a “mitigation” measure. Following the decision in Briels, the Court clarified that a proposal could never amount to a “mitigation”, rather than “compensation”measure where the project would result in a loss of part of the SAC. The fact that the proposal to create the new nature reserves would be implemented before the adverse effect (i.e. the loss of part of the SAC) impacted on the SAC had no bearing on this conclusion.

The Court emphasised (as has been held previously) the point that national competent authorities should only approve a proposed plan or project where they are certain that it will not adversely affect the integrity of the protected site. The Court pointed out that it is difficult to assess the positive effects of new habitat to be created in the future with any degree of certainty, the effects of which will only be certain in several years' time. In this case, the adverse effects on the SAC site from the development project were certain, but the benefits from the creation of the new nature reserves were not certain.