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NCCOS Project

Marshes on the Margins: Developing Tidal Wetlands Adaptation Strategies in Southern California

This project began in September 2016 and is projected to be completed in August 2020

We will investigate how the dynamic and heavily altered (e.g., through jetty construction or dredging) estuaries of Southern California will be affected by sea level rise. We will also identify nature-based conservation and restoration strategies to mitigate the impacts of sea level rise, and share these tools with local stakeholders and coastal managers by building on the collaborative work of the Southern California Wetlands Recovery Project partnership.

Why We Care
Approximately 98 percent of tidal wetlands in Southern California were historically intermittently open to tidal action. The diverse and seasonally varying habitats provided by intermittently open estuaries serve a wide variety of estuarine species. However, very few estuaries in Southern California still exhibit natural cycles of intermittency, and many are managed as permanently open systems either through construction of jetties, or through dredging.

The conversion from intermittent dynamics to permanently open leads to a reduction of habitat diversity in the region and a reduction in the support of certain NOAA trust species, such as tidewater gobies and juvenile steelhead. Wetlands around these estuaries also host a number of endangered and threatened plant and animal species. Very little data and understanding exists about intermittently open estuaries in Southern California, and resource managers frequently need better information to make management decisions. Because the patterns of opening and closure in tidal wetlands is likely to change with rising sea levels, we have an opportunity and a need to rethink management of these systems, and to better understand the trade-offs between various management scenarios.

What We Are Doing
Our project will have four stages: 1) identifying the vulnerability of intermittently open estuaries, 2) developing natural and nature-based adaptive strategies, 3) implementing these developed tools at case study sites, and 4) leveraging existing coastal management networks to share outcomes and promote management solutions that rely on natural and nature-based features.

First, the project team will model, analyze, and quantify the vulnerabilities and response of intermittently open estuaries and tidal wetlands to sea level rise. Next, the team will identify and quantify opportunities for natural restoration through construction of nature-based features. The tools will be applied at two to four wetland systems in Southern California. Finally, the project team will leverage existing scientific, management, and practitioner networks, developed through the Southern California Wetlands Recovery Project, to gain input during the project’s product development stage and to promote inclusion of natural and nature-based features in the wider range of adaptation strategies available to coastal managers. These steps are expected to improve the number of tools available for managing intermittently open estuaries in Southern California.

What We’ve Accomplished
The team delivered restoration guidance products to Southern California Wetlands Recovery Project (WRP)'s Marsh Adaptation Planning Tool (MAPT) and hosted meetings to present model results to WRP members and receive feedback to improve the utility of the outputs. This led to Los Cerritos wetlands including transition zone restoration guidance in their restoration plans, Goleta Slough wetlands identifying the need for a restoration project, Los Peñasquitos Lagoon including modeling results into the north parking lot climate adaptation project, and the Tijuana Estuary Tidal Restoration Program including modeling results into their restoration project.

The project is led by the California State Coastal Conservancy (South Coast Region), and is funded through the Ecological Effects of Sea Level Rise (EESLR) Program. The project team will leverage results and products from a previous EESLR-funded sediment and natural and nature-based features study in Southern California, particularly at the Tijuana Slough National Estuarine Research Reserve. Project partners include the California State Coastal Conservancy (South Coast Region); the University of California, Davis; and the U.S. Geological Survey.

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