Between ecology and legal regulation: The status of green roofs as an equivalent of biologically active area in Polish law

This article examines the status of green roofs as an equivalent of biologically active area in Polish law, with particular attention to stormwater retention and the durability of vegetation. The study combines dogmatic legal analysis of planning and technical building regulations and administrative court jurisprudence with a review of scientific literature and the authors’ field research on extensive green roofs. The analysis identifies an inconsistency between the statutory definition of biologically active area and the technical building definition of biologically active terrain: the former does not expressly require stormwater retention for terraces and flat roofs, whereas the latter does. The uniform rule crediting 50% of their area does not reflect differences in hydrological performance and ecological potential. The empirical findings indicate the importance of vegetation for substrate microbial activity, but did not demonstrate a statistically significant effect of plant density on retention during the initial years of the experiment. The article argues for coordinating the two legal definitions and linking the qualification of green roofs to verifiable technical and functional parameters, including retention capacity and conditions for durable vegetation. Such an approach would strengthen the relationship between formal compliance and the environmental objectives of regulation.