61In order to determine the nature of any compensatory measures, the damage to the site concerned must be precisely identified. Knowledge of those implications in the light of the conservation objectives relating to the site in question is a necessary prerequisite for the application of Article 6(4) of the Habitats Directive, since, in the absence of those elements, no condition for the application of that derogating provision can be assessed. The assessment of any imperative reasons of overriding public interest and that 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 (see, to that effect, judgment of 14 January 2016 in Grüne Liga Sachsen and Others, C‑399/14, EU:C:2016:10, paragraph 57 and the case-law cited)