Integrating Nature-based Solutions (NbS) into urban infrastructure planning is critical to address the increasing impacts of climate risk, biodiversity loss, and threats to human health and wellbeing. Agriculture, Forestry, and Other Land Use (AFOLU) are among the largest emitters due to rapid urbanisation, accounting for 24% of greenhouse gas emissions and further exacerbating extreme events that pose significant threats to existing infrastructure and vulnerable communities in global cities. This situation underscores the urgent need for NbS as an innovative solution to adapt and mitigate disparities caused by climate change. NbS with Blue-Green Infrastructure (BGI) – combining blue (water bodies) and green (vegetation) infrastructures – can reduce runoff, manage water sustainably, and address urban heat. NbS can contribute 37% of the climate mitigation needed by 2030, and provide co-benefits to address land degradation and biodiversity loss.

G20 countries play a key role in promoting NbS, with previous presidencies and T20 policy briefs advocating for its scaling up. Multilateral organisations such as UNFCCC, UNEP, and IPCC also promote their integration into infrastructure projects for climate resilience and sustainable development. However, implementing BGI still faces challenges, such as funding gaps, standard variations, limited cross-sector collaboration, and inadequate consideration of local characteristics, especially in Global South cities. The G20 is encouraged to lead the mainstreaming of BGI. Firstly, develop BGI standards that can be replicated into national and city regulations and aligned with global frameworks. Secondly, innovative financing, such as green bonds and co- financing systems, should be mobilised, with a focus on vulnerable developing countries. Thirdly, platforms for community engagement should be built to share good practices and ensure BGI projects are developed with local communities, integrate traditional knowledge, and meet their socio-economic needs. Lastly, collaborative governance should be built with robust stakeholder engagement and connectivity across countries, and sectors should be promoted with a watershed governance approach to ensure equitable implementation and address transboundary climate issues. By prioritising BGI, the G20 can demonstrate the tangible benefits of NbS for people and the planet, provide co-benefits, and create resilient cities and communities.