Nature based solutions (NBSs) can play a key role in adapting to climate changes, especially when it comes to sea level rise, storm surges, and extreme rainfall. To better understand the full effects of nature-based solutions, positive externalities such as public health, biodiversity, water purification, carbon sequestration and other ecosystem services (ESSs) can be included in the cost benefit analyses (CBAs) conducted to inform the decision upon what solution to use for the climate change adaption.
In the report we present six NBS case studies from the Nordic countries where the positive externalities are monetised and discuss how this affects the outcome of CBAs. Benefit transfer (or more general; value transfer) techniques are used to transfer estimates from previously published and peer-reviewed environmental valuation studies to our six case study sites.
Our results indicate that the inclusion of positive externalities in CBAs leads to a substantial increase in the social benefits of NBS, which could potentially change the outcome of CBAs from net costs to net benefits of the project. We end by discussing how CBAs can benefit from inclusion of positive externalities when CBAs are used to inform decisions makers on how to choose the most efficient measures to adapt to water-related climate change impacts.