Competent authorities (usually Local Planning Authorities) are required to undertake a Habitats Regulations Assessment (HRA) where proposed plans or projects may have a likely significant effect on a European site (Natura 2000 site). European sites include Special Protection Areas and Special Areas of Conservation. In the UK, Ramsar sites are also required to undergo a HRA when a plan or project is considered likely to have a significant effect.
The HRA starts by screening a proposed plan or project to decide whether it is likely to have a significant effect on the European site. If no significant effects are identified at this stage, then no further assessments are required and the plan or project can be “screened out” of the HRA process. If it cannot be satisfactorily demonstrated that significant effects are unlikely, a full Appropriate Assessment will be required to establish whether the project will actually result in a significant adverse effect upon European sites.

In 2008 Sullivan J, ruling on the Dilly Lane case, stated that mitigation measures that were “incorporated into the project” or which “formed part of the project” could be taken into account at the screening stage. This meant that many projects could be screened out of a full Appropriate Assessment because mitigation measures to avoid effects on European sites were incorporated into the planning application. However, a recent decision by the Court of Justice of the European Union (CJEU), on the People Over Wind and Sweetman v Coillte Teoranta (C-323/17) case, means that measures intended to avoid or reduce the harmful effects of a proposed project on a European site cannot now be taken into account at the screening stage of the HRA.

The CJEU reached the following conclusion on mitigation and avoidance measures:
“In the light of all the foregoing considerations, the answer to the question referred is that Article 6(3) of the Habitats Directive must be interpreted as meaning that, in order to determine whether it is necessary to carry out, subsequently, an appropriate assessment of the implications, for a site concerned, of a plan or project, it is not appropriate, at the screening stage, to take account of the measures intended to avoid or reduce the harmful effects of the plan or project on that site” (paragraph 40).

Importantly, the CJEU stated that “taking account of such [avoidance / reduction] measures at the screening stage would be liable to compromise the practical effect of the Habitats Directive in general, and the assessment stage in particular, as the latter stage would be deprived of its purpose and there would be a risk of circumvention of that stage, which constitutes, however, an essential safeguard provided for by the directive” (paragraph 37).

The implication of this ruling is that many more projects will require a full Appropriate Assessment before planning permission can be granted.