Green infrastructure integration in informal settlements: Assessing climate resilience outcomes in sub-Saharan African cities. A systematic review

Sub-Saharan Africa (SSA) is urbanising faster than any other region in the world, with approximately 60% of its urban population residing in informal settlements. These are acutely vulnerable to climate-related hazards, including flooding, extreme heat, and water scarcity. Green infrastructure (GI) includes nature-based solutions such as urban trees, rain gardens, bioswales, constructed wetlands, and permeable paving. GI is increasingly promoted to strengthen climate resilience, although its cost-effectiveness compared with conventional infrastructure remains insufficiently evaluated. Nevertheless, empirical evidence from SSA informal settlement contexts remains fragmented and geographically uneven. This study synthesised peer-reviewed and credible grey literature evidence published between 2015 and 2026 on GI integration in informal settlements across cities in SSA. It examines: (i) typologies of GI implemented; (ii) documented climate resilience outcomes, including stormwater management, urban heat island (UHI) mitigation, and flood-risk reduction; (iii) governance, institutional, and financial barriers; and (iv) community participation frameworks. Findings indicate that GI offers considerable potential for multi-scalar resilience benefits. Evidence is moderate for stormwater management, flood-risk reduction, urban heat-island mitigation, and food security. However, it is limited to moderate for drought resilience, biodiversity, and health and social cohesion outcomes. It remains limited for air quality, erosion control, and spatial-equity outcomes. Scaling is further impeded by insecure land tenure, governance fragmentation, inadequate financing, and limited institutional capacity. The study recommends community co-design, hybrid grey-green infrastructure, and dedicated urban climate finance.