In its judgment of February 26, 2026, in Case C-131/24, the European Court of Justice ("ECJ") clarified a key legal issue in European species protection law, thereby creating considerable legal certainty for infrastructure projects. The Court clarified that project-specific protection and mitigation measures (CEF measures) may already be taken into account when assessing whether a species protection prohibition applies and that their effectiveness does not have to be proven by means of a practically impossible "1:1 practical proof." The judgment sets an important benchmark for approval practice.

Background and initial proceedings

The preliminary ruling proceedings were triggered by the "L5181, Spange Wörth" road construction project. Environmental organizations opposed the approval of the project and argued in the appeal proceedings, in particular, that the predicted traffic load would cause significant disturbance to strictly protected bird species, including the middle spotted woodpecker. The Federal Administrative Court ("BVwG") then referred two key questions to the ECJ regarding the interpretation of the prohibition of disturbance under Article 5(d) of the Birds Directive. Essentially, the questions concerned:

1. whether damage prevention and mitigation measures (CEF measures) may already be taken into account when examining whether there is a prohibition under species protection law, and
2. what requirements must be imposed on scientific evidence of their effectiveness.

Key points of the ECJ ruling

The ECJ confirmed that project-related avoidance and mitigation measures may already be taken into account when assessing whether there is a prohibited disturbance within the meaning of the Birds Directive, and that the question of disturbance does not depend on the disturbance of the individual, but rather on the level of the population.

The decisive factor is whether such measures ensure that the project does not significantly affect the objectives of the Birds Directive, in particular the maintenance of stable populations of the species concerned. If this is guaranteed, there is no prohibited disturbance in fact. 

In doing so, the ECJ has once again clearly rejected a counterargument that is frequently put forward in practice. In particular, the Court clarified that the strict assessment criteria of habitat protection law (especially in connection with Natura 2000 areas) cannot be applied across the board to general species protection.

Equally significant is the Court's second clarification regarding the requirements for scientific proof of the effectiveness of protective measures. The ECJ ruled that it is not necessary for the effectiveness of a measure to have been proven beforehand under identical practical conditions. Rather, a well-founded expert assessment is sufficient, provided that it is based on the best available scientific knowledge and a plausible analysis of nature conservation. 

Practical significance for infrastructure projects and approval procedures

The Court thus expressly recognized the special nature of ecological forecasts. Unlike technical systems, biological processes cannot be reproduced under laboratory conditions or predicted with absolute certainty. The requirement for an identical preliminary practical test would therefore constitute a de facto insurmountable hurdle to approval and make the application of protective measures impossible in practice. This clarification removes one of the greatest uncertainties in previous approval practice.

In future, project applicants can rest assured that technically sound and effective protective measures will already be taken into account at the factual level and that a qualified expert prognosis based on current scientific findings will suffice. 

Conclusion and outlook

With its ruling C-131/24, the ECJ strikes a crucial balance between effective species protection and the feasibility of necessary infrastructure projects. The Court clarifies that modern species protection must not be blocked by unrealistic standards of proof, but must be based on scientifically sound forecasts and effective protection measures, thus maintaining the necessary flexibility.

For project developers, this means a significant gain in legal and planning certainty. At the same time, the high level of protection afforded by European species protection law is maintained, as a thorough nature conservation assessment and effective protection measures are still required.