The democratisation of European nature governance 1992–2015: introducing the comparative nature governance index

European environmental governance has radically transformed over the past two decades. While traditionally enforcement of environmental law has been the responsibility of public authorities (public authorities of the EU Member States, themselves policed by the European Commission), this paradigm has now taken a democratic turn. Led by changes in international environmental law and in particular the UNECE Aarhus Convention (UNECE, United Nations Economic Commission for Europe Convention (1998). Convention on access to information, public participation in decision-making and Access to Justice in Environmental Matters (the Aarhus Convention), signed on June 25, 1998.), EU law now gives important legal rights to members of the public and environmental non-governmental organisations (“ENGOs”) to become involved in environmental governance, by means of accessing environmental information, participating in environmental decision-making and bringing legal proceedings. While doctrinal legal and regulatory scholarship on this embrace of “bottom-up” private environmental governance is now substantial, there has been relatively little quantitative research in the field. This article represents a first step in mapping this evolution of environmental governance laws in the EU. We employ a leximetrics methodology, coding over 6000 environmental governance laws from three levels of legal sources (international, EU and national), to provide the first systematic data showing the transformation of European environmental governance regimes. We develop the Nature Governance Index (“NGI”) to measure how the enforcement tools deployed in international, EU and national law have changed over time, from the birth of the EU’s flagship nature conservation law, the 1992 Habitats Directive (Directive 92/43/EEC). At the national level, we focus on three EU Member States (France, Ireland and the Netherlands) to enable a fine-grained measurement of the changes in national nature governance laws over time. This article introduces our unique datasets and the NGI, describes the process used to collect the datasets and its limitations, and compares the evolution in laws at the international, EU and national levels over the 23-year period from 1992–2015. Our findings provide strong empirical confirmation of the democratic turn in European environmental governance, while revealing the significant divergences between legal systems that remain absent express harmonisation of the Aarhus Convention’s principles in EU law. Our data also set the foundations for future quantitative legal research, enabling deeper analysis of the relationships between the different levels of multilevel environmental governance.