Protection and restoration of coastal habitats yield multiple benefits for urban residents as sea levels rise

A new study in npj Urban Sustainability reveals the add-on benefits of NbS such as conserving marshlands and restoring beaches, which are protecting against sea-level rise as well as concrete sea walls. This is in addition to further additional benefits including climate change mitigation through carbon storage, nutrient pollution reduction, and opportunities for recreation, incentivising policymakers to prioritise NbS for sea-level rise.

California is amongst the US states most exposed to sea-level rise, with the San Francisco Bay Area is particularly at-risk. Within the Bay Area, San Mateo County is at particular risk of exposure to flooding and erosion over the next 50–100 years, with the population more vulnerable to the effects of sea-level rise due to demographic factors including age, race, income, and housing vulnerability.

Three scenarios were modelled for seal-level rise adaption, with input from stakeholder workshops and testing of the suitability of stretches of shoreline for restoration of different coastal habitats. Scenario 1 modelled concreate seawalls across the  San Francisco Bay coastline. Scenario 2 considered conservation and restoration projects currently underway or in various stages of planning, such as rehabilitation of salt ponds and the addition of a beach in front of a levee. Scenario 3 explored additional NbS projects, such as protecting marshlands and restoring native seagrasses and oyster beds along the coastline.

Extra benefits from adaptation options were modelled. Scenario 2 – with NbS projects already being implemented – provides 6 times more storm water pollution reduction than concrete seawalls. Scenario 3 including proposed additional NbS projects, would result in 8 times more storm-water pollution reduction than traditional approaches.

The results informed guiding principles for the county’s sea-level rise adaptation planning, including to prioritize NbS, use an inclusive, equitable, and community-based process to make decisions, and rigorously track the process to reduce vulnerability, risks, and impacts. This case adds to the evidence base that NbS help protect coastlines while yielding diverse ecosystem services.