Bridging NbS and legal literature: Institutional, procedural and substantive barriers to nature-based solutions implementation

Nature-based solutions (NbS) are considered key measures for tackling various environmental challenges and attaining multiple urban sustainability goals. In recent years, the barriers to urban NbS implementation have been increasingly discussed by the literature in an effort to highlight what factors impede widespread NbS in cities. However, the urban NbS literature generally neglects the legal perspective of these barriers, which have been rarely highlighted and assessed through a legal lens, despite the significant role that the law plays in influencing urban sustainability transitions. Thus, a legal perspective seems to be missing from the current literature on barriers to urban NbS implementation. This paper aims to test this hypothesis and, by connecting some of these barriers with relevant ongoing discussions in the legal literature, to establish an agenda for future legal research on NbS. To do so, a scoping review is firstly conducted on the literature on governance- and policy-related barriers to urban NbS implementation. The review reveals a number of barriers which, although not discussed from a legal perspective in the literature, can be divided into three categories, namely institutional, procedural and substantive. The main findings of the review are then discussed in the light of the current debates in the legal literature on the division of powers, participatory rights, and the notion of ownership. This analysis demonstrates how some of the issues raised by the legal literature are similar and, at times, overlapping with the problems encountered when implementing urban NbS. The agenda resulting from this comparison suggests that future legal research on NbS should focus on facilitating decentralised governance approaches, enable tailored and easily enforceable public participation mechanisms, and promote the reconsideration of private land ownership on the basis of its socio-environmental function.