Wetlands and Marshes

Ribbons of open water snake through wetland vegetation.
Schooner Bay Wetlands.

Where freshwater streams meet saltwater, they form estuaries—one of the most fertile habitats on earth. These rich habitats provide spawning grounds for crabs and numerous fish species, and are a vital stopping point for migratory ducks and shorebirds as they fly thousands of miles up and down the Pacific Flyway.

The shores of an estuary are often fringed with wetlands—a generic term used to describe a variety of habitats where the land is at least sometimes covered with water. Salt marshes are a particular kind of wetland that occurs in saline environments, like near estuaries or bays. Common freshwater wetlands can include marshes and swamps. Another type of wetland habitat is riparian habitat, which is found along streams and lakes and typically supports verdant stands of water-loving plants. In all of these kinds of wetlands, submerged and partially submerged vegetation provide food and refuge for a myriad of species, and also capture sediment and pollutants.

Wetlands play an important role in the health of aquatic and terrestrial ecosystems. They provide valuable functions for humans and wildlife such as storing floodwaters, dissipating energy of flood flows, improving water quality, providing habitat and food for wildlife, as well as providing recreational opportunities and support of mariculture and fisheries industries. Loss or degradation of wetlands eliminate or substantially reduce the potential for wetlands to serve some of these important functions.

Land development has claimed much of the wetland habitat in the Bay Area, but a number of restoration projects, including those spearheaded by the National Park Service and its partners at Drakes Estero, Estero de Limantour, and the Giacomini Wetlands, are attempting to reverse that trend.

Giacomini Wetland Restoration Project

In the 1940s, the Giacomini family, with the support of the Army Corps of Engineers, had constructed a system of levees at the head (e.g., south end) of Tomales Bay, in order to "reclaim" land and convert the wetlands into pasturelands. However, the levees dramatically reduced floodwater retention in the floodplains of Lagunitas Creek and Tomasini Creek, with the levees along Lagunitas Creek potentially exacerbating flooding of adjacent private properties. Removal of riparian vegetation on levees had also decreased the ability of riparian systems to dissipate the energy of flood flows, leading to faster, more turbulent, and erosive flows. In Olema Marsh, steadily increasing water surface levels created by poor drainage of Bear Valley Creek flows had not only reduced the potential volume of floodwater that can be stored, but increased flooding of adjacent county roadways, such as Levee Road (the locals' name for Sir Francis Drake Boulevard between Point Reyes Station and Inverness Park) and Bear Valley Road.

In 2000, the National Park Service acquired the Waldo Giacomini Ranch at the head (e.g., south end) of Tomales Bay for the purpose of wetland restoration using a combination of Congressional appropriations and mitigation monies from the California Department of Transportation. While the Giacomini Ranch and Olema Marsh, by 2000, were largely wetland and home to at least two federally listed threatened or endangered species, their value to the larger Lagunitas Creek and Tomales Bay ecosystems had been greatly diminished by land degradation and the lack of hydrologic connectivity. Wetlands on the Giacomini Ranch largely consisted of expanses of wet pasturelands created through seeding of nonnative grasses and herbs. With such low biodiversity, the pasturelands lacked the structural habitat diversity so important to wildlife. The conversion of Olema Marsh to freshwater marsh through diking had ostensibly increased its attractiveness to some wildlife species, such as waterbirds, but it had likely also displaced species that could have historically occurred in the transitional zone between fresh and salt water, such as the federally listed endangered species, tidewater goby (Eucyclogobius newberryi).

 
A large, orange excavator removes a section of a levee as water starts to flow through the breach.
An excavator breaches a levee on October 26, 2008.

From 2000 to 2008, the National Park Service, with its partners, engaged the public in the planning process for the restoration of the Giaocomini Wetlands. Construction of the restoration component of the Giacomini Wetland Restoration Project was implemented in two principal phases-Phase I in fall 2007 and Phase II in summer and fall 2008. Phase I, which spanned from September 2007 through December 2007, principally involved removal of agricultural infrastructure and conditions and creation of special status species habitat. The second and largest phase of the project was Phase II, which ran from July 2008 through December 2008. Phase II focused on marshplain and floodplain restoration, with the climax occurring on October 26, 2008, when levees were breached, allowing salt water to flow across an area from which it had been excluded for decades. Visit our Giacomini Wetland Restoration Project: Summary of Construction Under Phase I and II page to learn more details.

Construction efforts aimed at restoring the former Waldo Giacomini Ranch to wetland were largely complete as of December 2008. However, this did not mean that restoration or construction was entirely complete. Additional construction may occur in future years in the Giacomini Ranch and Olema Marsh should additional funding become available. These restoration activities include continued restoration of hydraulic connectivity in Olema Marsh and further lowering of high elevation areas in the Giacomini Ranch, as well as continued treatment and retreatment of non-native invasive plant species.

 
A photograph of green wetland vegetation in the foreground, some open water in the middle distance, and trees and grass covered hills in the far distance. and
The Giacomini Wetlands on September 9, 2013, nearly five years after the breaching of the levees.

Restoration, too, is an ongoing process. While the bulldozers and excavators may be gone, the process of restoring these diked and altered systems to fully functional marshes is just beginning and will continue to unfold into the future. Please visit our Restoration web pages for updates and information on the status of the restoration process.

Learn More

Dave Schirokauer and Amy Parravano. 2006. Enhanced wetlands mapping and inventory in Point Reyes National Seashore and Golden Gate National Recreation Area. Park Science 23(1).

Visit the Pacific Coast Science and Learning Center's Wetlands & Estuaries pages.

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    Pacific Coast Science and Learning Center Research Project Summaries

    From 2006 to 2009, Pacific Coast Science and Learning Center (PCSLC) communication interns assisted scientists conducting research through the PCSLC and the San Francisco Bay Area Inventory & Monitoring Network to produce a series of Resource Project Summaries, four of which were about wetlands and wetland species at Point Reyes. These two-page summaries provide information about the questions that the researchers hoped to answer, details about the project and methods, and the results of the research projects in a way that is easy to understand.

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    Last updated: July 23, 2020

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