Nature-based solutions as climate change adaptation measures for rail infrastructure

The transport sector fulfils crucial economic and social functions with railways being instrumental in the safe, efficient, and reliable movements of people to their destinations and goods to market. One of the most critical vulnerabilities in the railway transport system is the low flexibility of both infrastructure and operations in the event of disturbances including those caused by extreme weather events such as floods, droughts, storm surges and temperature extremes. With the frequency and intensity of such events being projected to increase, the failure to proactively consider the impacts of a changing climate on new and existing infrastructure raises the possibility of increased service disruption and adverse economic impacts as climate change progresses. Nature-based solutions (NbS) present long-lasting, cost-effective and environmentally sustainable climate change adaptation (CCA) options. However, as an effective alternative or complement to grey (engineered) solutions, they are still in their infancy, especially within the railway sector. To date very few studies have investigated the role of NbS for CCA in the railway transport system. Recognising the importance of the rail industry's need to adapt its infrastructure to accommodate current weather extremes and a changing climate, this review paper examines NbS being used as CCA measures both in the rail context, and in non-rail contexts which may be transferable to the rail sector. Our review demonstrates that there are significant knowledge gaps that may hinder the uptake of NbS in the rail environment which warrant further research to support the inclusion of NbS as viable CCA options for rail infrastructure. Better understanding of these issues is required for the development of rail sector specific guidance and will enable better design, implementation, and dissemination of NbS as credible alternatives or complements, and more sustainable CCA measures