Monetary evaluation of co-benefits of nature-based flood risk reduction infrastructure to promote climate justice

Climate change disproportionately impacts socially and economically marginalized populations. To rectify this imbalance, adaptation plans can explicitly include projects that not only lower the threat for these populations but also may provide co-benefits that improve the quality of their lives. One method to evaluate these co-benefits or any additional costs to these populations in the analysis of adaptation options is to monetize them. Monetization will convert these generally non-market impacts into monetary units and allow them to compared with each other as well as other market impacts in benefit–cost analyses. The monetized values can also be weighted by the utility of these benefits and costs to the different socio-economic groups in a population. Using illustrative case studies in two areas of Boston USA with different socio-economic conditions but similar population sizes and flood threats, this evaluation approach is tested when using nature-based solutions (NBS) to lower flood threats. The non-market benefits and costs included are improved air quality, availability of public transportation, recreational space, rent escalation due to gentrification, and prevented loss of wages due to reduction in mental stress. Utility is an inverse function of annual income. The case studies illustrate that by quantifying the non-market impacts the value of including adaptation actions that promote climate justice co-benefits can be shown.