Hidden patterns in fauna compensation values in European biodiversity legislation.

Biodiversity laws in several European countries rely on official species-level price lists for fauna to enable compensation for biodiversity damage. However, the methods underlying these values are often opaque and poorly justified, raising concerns about consistency, fairness and ecological relevance. To gain insights into the revealed public regulatory patterns embedded in these mechanisms, we investigate how monetary compensation values are assigned to fauna in European biodiversity legislation and what factors influence these values. Here we show that species-level values are implicitly guided by biological traits and taxonomic biases, based on a dataset of 9,971 species across 24 countries. Our analysis reveals that mammals and birds receive disproportionately higher values, while traits such as generation length and protection status also significantly influence values. These findings reveal hidden criteria that shape regulatory decisions and enhance our understanding of conservation priorities. We recommend integrating systematic, science-based criteria into legal valuation practices, supported by collaboration between conservation scientists and legal practitioners.