Nature-based solutions (NbS) have emerged as a key strategy for sustainably addressing multiple urban challenges, with rapidly increasing knowledge production requiring synthesis to better understand whether and how NbS work in different social, ecological, economic, or governance contexts. Insights in this Perspective are drawn from a thematic review of 61 NbS review articles supported by an expert assessment of NbS knowledge in seven global regions to examine key challenges, fill gaps in Global South assessment, and provide insights for scaling up NbS for impact in cities. Eight NbS challenges emerged from our review of NbS reviews including conceptual, thematic, geographic, ecological, inclusivity, health, governance, and systems challenges. An additional expert assessment reviewing literature and cases in seven global regions further revealed the following: 1) Local context-based ecological knowledge is essential for NbS success; 2) Improved technical knowledge is required for planning and designing NbS; 3) NbS need to be included in all levels of planning and governance; 4) Putting justice and equity at the center of urban NbS approaches is critical, and 5) Inclusive and participatory governance processes will be key to long-term success of NbS. We synthesized findings from the NbS review results and regional expert assessments to offer four critical pathways for scaling up NbS: 1) foster new NbS research, technological innovation, and learning, 2) build a global NbS alliance for sharing knowledge, 3) ensure a systems approach to NbS planning and implementation, and 4) increase financing and political will for diverse NbS implementation.

The world is confronting a range of ‘wicked problems’ that defy simple, linear solutions. Increasingly, the range of challenges including poverty, climate change and environmental degradation require solutions that cannot be drawn from a single knowledge base. Although excellent environmental legislation exists in South Africa (including that relating to climate change), it alone is not sufficient to solve the challenges the country faces. Rather, science that builds knowledge through engagement with a variety of actors, their views, expertise and perspectives, including mutual and transgressive learning, is required. This paper presents three South African case studies that reflect on the value of adopting transdisciplinary (TD) and co-production of knowledge (CPK) approaches to environmental problem-solving. Although not without their challenges, TD and CPK are inclusive approaches which usually enable a wider framing of environmental challenges and their ownership by various publics, and pave the way for effective implementation of solutions and actions.

Non-technical summary: There are significant challenges to retaining indigenous biodiversity and ecological infrastructure in African cities. These include a lack of formal protection and status for remnant ecologically functional patches rendering them open toad hochuman settlement, which is in part linked to weak governance and management emerging from complex histories, and competing crisis-ridden demands. Persistent gaps in knowledge and practice mean that the social, economic, development and well-being benefits of ecological infrastructure are not understood or demonstrated. Addressing these challenges requires the adoption of multiple top-down government interventions and bottom-up community and neighbourhood actions. The development of detailed case studies that engage with knowledge generation and sharing at multiple scales through co-learning practices will also help create a much-needed deeper understanding of development options within this context.

While government housing can raise living standards for the urban poor, it has environmental impacts and contributes to urban resource consumption. In Gauteng Province, South Africa, government housing aims to improve quality of life, reduce poverty and inequality, and transform unsustainable urban forms. This paper draws on survey and interview data to explore the social justice and environmental sustainability outcomes of Gauteng’s government housing programmes. The data reveal improved access to basic services and amenities. However, the developments tend to be poorly located with regard to economic opportunities, and residents are forced to explore other income generation opportunities. This paper highlights the complex interplay between justice and sustainability, where the outcomes are aligned in some instances and conflictual in others. It points to the need to move beyond linear, reductionist relationships between justice and sustainability to further the conceptual understanding of their interlinkages.