A framework to facilitate inclusion of NbS ecosystem service benefits in cost-benefit analysis

Uncertainty and perceived lack of quantifiability in the evaluation of nature-based solution (NbS) benefits relating to non-market ecosystem services remains a barrier to the ready adoption of NbS as water resilience projects. We aim to bridge this gap for coastal and riverine NbS by creating a framework to improve inclusion of the entire range of ecosystem services provided by NbS in cost-benefit analysis of water resilience project alternatives. We have conducted a literature review of NbS and natural and nature-based feature (NNBF) literature and case studies to determine which ecosystem services are associated with wetlands, dunes and beaches, seagrass meadows, barrier islands, and forested ecosystems. Through the review, we have identified ecological and environmental, carbon capture, coastal land loss reduction, hazard risk reduction, socio-economic and cultural, and economic and financial services of each NbS type, along with the range of metrics currently used to evaluate project output of these benefits. We created a fully cited framework detailing the benefits and metrics for each NbS type, and implemented it in both a knowledge graph and interactive radial graph formats. The interactive radial graph provides support for human user exploration of the framework and cited literature and case studies. The knowledge graph will serve to support retrieval-augmented generative agent tools in the future. In future work, we will improve on the framework with inclusion of cost and limitation information, as well as a basic method for estimating market values of non-market benefits based on those of market benefits.