Climate as the Primary Moderator: Towards Context-Driven Design and Implementation of Vertical Greenery Systems for Stormwater Management

Urbanisation intensifies stormwater management challenges by expanding impervious surfaces, increasing flood risk and degrading water quality. Vertical Greenery Systems (VGS) are increasingly promoted as nature-based solutions for space-constrained cities, yet their performance remains highly variable and context-dependent. This systematic review, conducted in accordance with PRISMA guidelines and synthesising evidence from 34 peer-reviewed studies, demonstrates that VGS hydrological efficacy is not a universal constant but is fundamentally moderated by local climatic conditions. Climate acts as the primary filter, shaping system function across tropical, temperate, Mediterranean, arid, and cold zones, each presenting distinct opportunities and constraints. Beyond climate, performance is refined by system typology (green façades versus living walls), plant functional traits (notably root architecture), and substrate composition, which together determine trade-offs between runoff delay, retention, and water quality improvement. The review further reveals a stark divergence in adoption barriers: in the Global North, high costs, regulatory complexity, and data gaps create institutional inertia, whereas in the Global South, limited awareness, misaligned priorities, and weak policy frameworks relegate stormwater management to a low priority. To address these challenges, we propose a five-pillar implementation framework centred on climate-responsive design protocols, advanced economic valuation of co-benefits, adaptive governance, long-term monitoring, and context-sensitive community engagement. This review provides actionable, evidence-based guidance for integrating VGS as resilient, equitable, and multifunctional components of sustainable urban water management, tailored not to global templates, but to local environmental and socio-institutional realities.