Integrating the Grey, Green, and Blue in Cities: Nature-Based Solutions for Climate Change Adaptation and Risk Reduction

Abstract

Cities are high emitters of greenhouse gases and are drivers of environmental modification, often leading to degradation and fragmentation of ecosystems at local and regional scales. Linked to these trends is a growing threat experienced by urban areas: the risk from hydro-meteorological and climatological hazards, further accentuated by climate change. Ecosystems and their services, though often overlooked or degraded, can provide multiple hazard regulating functions such as coastal and surface flood regulation, temperature regulation and erosion control. Engineering or grey approaches often do not tackle the root causes of risk and can increase the vulnerability of populations over the long-term. However, evidence of alternative approaches such as the role of healthy, functioning ecosystems in disaster risk reduction are still scarce, contentious, and with limited applicability in the urban context. This chapter explores the role of grey, green, and blue infrastructure and in particular hybrid approaches for disaster risk reduction and climate change adaptation to shed light on available sustainable adaptation opportunities in cities and urban areas. We highlight the dependence of cities on ecosystems as a key component of climate resilience building through case studies and literature review. At the same time, we highlight the limitation and drawbacks in the adoption of merely grey or merely green infrastructures. We suggest that an intermediate ‘hybrid’ approach, which combines both blue, green and grey approaches, may be the most effective strategy for reducing risk to hazards in the urban context.