Wetland Restoration in the San Francisco Bay Delta and Pacific Northwest
Science Center Objects
Estuaries and healthy coastal habitats are among the most productive ecosystems on Earth. They provide a variety of benefits, including habitat and food for fish and wildlife, flood and erosion protection, improved water quality, increased carbon sequestration, as well as beautiful scenery and opportunities for recreation. Along the U.S. Pacific Coast, both the San Francisco Bay estuary and the Pacific Northwest are critical estuarine ecosystems that support a diverse array of wildlife and are inextricably linked to human health and well-being. WERC’s Dr. Susan De La Cruz and her team study wetland enhancements and restorations, develop innovative methods to examine restoration processes, and assess restoration benefits for wildlife.
Monitoring restoration projects is similar to financial accounting in business; both provide a way to track the progress of a project and to adapt to changing circumstances. Thus, it is critical to develop the monitoring and design of a restoration project simultaneously, to improve its success.
SAN FRANCISCO BAY DELTA
Salt Pond to Salt Marsh - Restoration and Management for Migratory Birds
More than 85% of historical tidal marsh acreage in the San Francisco Bay (SFB) and estuary have been diked or filled for agricultural uses or other urban interests, such as commercial salt harvesting. Despite substantial habitat loss, every year over half a million shorebirds and about 700,000 waterfowl rely on both mudflat and salt pond habitats to “fuel up” during their migration along the Pacific Flyway. The central challenge to the restorations is to balance the needs of migratory waterbird populations that depend on open water or tidal flat habitat with those of other wetland species that rely on tidal marsh habitat.
Salt pond restoration projects in both the north (http://scc.ca.gov/projects/san-francisco-bay/napa-river-salt-marsh-restoration-project/) and south (http://www.southbayrestoration.org/) SFB aim to restore tidal flow to thousands of acres of former salt evaporation ponds, with the goal of creating marshlands to enhance ecosystem functions by improving water quality and providing habitat for endangered species. While mature tidal marshes will benefit many species, several waterfowl and shorebird species may increasingly rely on managed or agricultural wetlands to support a greater density of waterbirds. Managed wetlands, such as diked salt ponds or wetlands with managed hydrology, can provide important high-tide roosting habitat for shorebirds, consistent foraging opportunities, and nesting habitat for a variety of species. However, physical and biological data are needed by the U.S. Department of the Interior and state resource management agencies to adequately design and adaptively manage restorations to optimize their ecological benefits. Dr. De La Cruz's team studies these former salt pond systems to answer key questions for restoration managers.
Optimizing Managed Pond Habitat for Migratory Birds
As diked baylands and salt ponds gradually convert back to tidal marsh, the remaining managed pond habitat will become increasingly important for migratory birds. The characteristics of a managed pond can influence the abundance and species composition of the waterbirds that use it. For example, diving ducks forage in relatively deeper areas, while small shorebirds forage in shallow water habitat. In addition to foraging habitat, waterbirds also require safe roosting habitat to rest. Dr. De La Cruz’s team measures waterbird abundances, foraging and roosting behavior, habitat selection, invertebrate food resources and physical features of managed ponds to identify ways to optimize foraging capacity and roosting opportunities for multiple species. These results can help managers create habitat conditions that are appropriate for multiple waterbird species and thus maximize the number of birds that can be supported in managed ponds during the key periods of wintering and spring migration.
Nisqually River Delta Ecosystem
The Nisqually Glacier on Mt. Rainier forms the headwaters of the Nisqually River. For about 80 miles, the Nisqually River meanders through forests, foothills, farmland, several towns, a reservoir, and eventually empties into the Nisqually River Delta in southern Puget Sound. The Billy Frank Jr. Nisqually National Wildlife Refuge and the Nisqually Indian Tribe have partnered to protect and restore the Nisqually River Delta. Together, they have reconnected almost 900 acres to Puget Sound waters. Their efforts represent significant advances towards the recovery of Puget Sound and one of the largest estuarine restorations in the Pacific Northwest. The USGS WERC is partnering with the Refuge and Nisqually Indian Tribe to measure restoration progress and benefits to fish and wildlife. To learn more on initial restoration progress, please visit: https://pubs.er.usgs.gov/publication/70173942
Restoring Foodwebs within a Habitat Mosaic
The restoring Nisqually River Delta is comprised of a mosaic of freshwater forests and riparian zones, transitional wetlands and forests, and saltwater tidal marsh, mud flats, and eelgrass beds. As salmonids like juvenile Chinook salmon migrate from their hatching sites in the Nisqually River, they use the entire estuarine habitat mosaic to feed and grow as they adjust to a saltwater environment and eventually enter the Puget Sound. Dr. De La Cruz and colleagues are assessing the success of this large-scale restoration in terms of foodwebs by quantifying invertebrate production and salmon diet in each habitat type used by juvenile Chinook during outmigration to the Puget Sound.
Salmonids consume a range of prey, including insects from the terrestrial environment, epifauna (creatures that live on vegetation, such as eelgrass blades), and invertebrates within the water column and sediment. Dr. De La Cruz and partners hypothesize that a large river restoration improves the growth of juvenile salmon through increased access to new delta habitats and enhanced availability of invertebrate food from distinct habitat types. The abundance and distribution of the diverse invertebrate communities (terrestrial, aquatic, benthic, epifauna) used by juvenile Chinook can vary by habitat type along a salinity gradient from a mostly freshwater, forested tidal environment, to emergent forested transition, estuary emergent marsh, delta mud flats, or saline eelgrass beds (Zostera marina).
Tidal marshes are among the most productive ecosystems on Earth. In addition to providing habitat and abundant food for fish and wildlife, coastal wetland soils accumulate carbon at rates higher than any other ecosystem. The term “Blue Carbon” refers to the ability of coastal ecosystems (tidal marshes, eelgrass beds, mangroves) to capture significant amounts of carbon dioxide (CO2) from the atmosphere and provide longterm storage of the carbon in wetland soils.
Therefore, estuarine restoration has significant potential to simultaneously increase carbon sequestration and ecosystem functioning for wildlife.
At the Nisqually River Delta, an interdisciplinary team of USGS researchers is assessing the restoration’s potential to diversify carbon sources for wildlife food webs as well as increase carbon storage within wetland soils. The goal is to compare the carbon co-benefits of food web support and carbon sequestration between restoring marshes and natural marshes. To accomplish this, the WERC team is quantifying atmospheric carbon dioxide and methane exchange as well as assessing the carbon that contributes to food webs compared to the carbon stored in soil.
By documenting the benefits of wetlands for wildlife and carbon storage, this project will provide the necessary data to link traditional objectives of protecting, restoring, and managing diverse wetlands to support a broad array of species with carbon sequestration initiatives.