Researchers and the public continue to learn benefits of Mission Bay’s wetlands

Pintail ducks can be seen in the Kendall Frost Marsh.
(Roy Little / San Diego Audubon Society)

Wetlands, or marshes, are just now beginning to be appreciated for their unique place in the ecosystem.

Formerly thought of as simply giant mud pits, for decades these areas, saturated with either fresh or salt water, have been considered unsightly and useless.

For decades, they have been filled in or dredged under the guise of reclamation.

But as researchers and scientists have increasingly learned about the benefits of wetlands, the marsh area of Mission Bay Park known as De Anza Cove has been highlighted as a huge potential benefit to not just the nearby ocean communities, but all of San Diego.

Jim Peugh, conservation chair for the San Diego Audubon Society, lists several benefits of wetlands in quick succession.

“Prime reasons for conserving the wetlands include water quality, wildlife habitat, passive recreation, carbon sequestration and protection against potential sea level rise,” Peugh said.

Audubon has been working to save birds and their environments in San Diego since 1948. According to its website,, San Diego County has more animals and plants on the endangered species list than any other county in the U.S.

Say’s phoebe in flight with an insect in its beak, taken at Kendall Frost Marsh.
(Craig Chaddock)

Habitats the plants and animals need have also been under threat. For the past few decades, little to nothing has been done to protect or conserve De Anza Cove, and the wetlands have continued to shrink in size, Peugh said.

“In the ‘50s, no one thought about the reasons to conserve wetland areas,” Peugh said. “We need to undo some of the damage we’ve done in the past and this is a perfect opportunity.”

The opportunity Peugh was referring to is the City of San Diego’s proposal to restore the wetlands in De Anza Cove.

Where to learn more

For the San Diego Audubon Society, visit

For ReWild Mission Bay, visit

Details on the De Anza Natural plan are at

For events and more at Kendall Frost Marsh, see

A draft Environmental Impact Report released in March 2023 by the city — known as De Anza Natural — is undergoing a series of community feedback meetings.

The San Diego Audubon Society and the ReWild Coalition have offered their own proposals for restoring the wetlands.

One of the major differences in the two plans is that ReWild Mission Bay (a project of the San Diego Audubon and ReWild Coalition partners) wants greater emphasis on maximum wetland restoration.

De Anza Cove lies within Mission Bay Park — the largest aquatic park of its kind. Mission Bay Park was created in the 1950s. Covering 27 miles of shoreline, it is equal parts land and water, and features numerous coves and even two islands. The park was created by dredging and filling what was originally about 4,000 acres of wetlands.

Although wetlands have important implications for wildlife, Kendall Frost Marsh — about 1 percent of the original salt water marsh habitat — is nearly all that remains. Located in Mission Bay, the marsh covers about 40 acres.

Although the marsh area isn’t large, it is home to a variety of birds, including the endangered Ridgway’s clapper rail and Belding’s savannah sparrow. The endangered California least tern nests nearby.

Great and snowy egrets, great and little blue herons, Cooper’s and red tailed hawks, Western sandpipers, marbled godwits, willets, brants, American Wigeons, black skimmers, Western Grebes and more are just some of the birds that make their home in the marsh.

Lesley Handa, lead ornithologist with the San Diego Audubon Society, has studied wetland areas for years.

“The biodiversity of the marsh is on par with San Diego Bay,” Handa said. “Most people want to study the area during the spring breeding season. But during the winter, there can be up to 58 species of water and shore birds.”

Belding’s savannah sparrow make their home in Kendall Frost Marsh; the species is endangered.
(Craig Chaddock)

She said every wetland is entirely unique from every other wetland, based on elevation, species, resources, human disturbance (or lack of it) and other factors. She added that birds rely on a network of wetlands to survive.

“Because Kendall Marsh is closed off, it attracts a lot of species sensitive to disturbance,” she said. “And for the Belding’s savannah sparrow and Ridgway’s rail, there is nowhere else for them to go.”

Peugh also pointed out the diversity of birds at the marsh, and how each one fills a unique niche.

“If you go to the wetlands and watch, at every stage of the tides there are different groups of birds foraging at different times,” Peugh said. “When the shorebirds are poking their bills in the sand or water, they are getting insects, eggs, crabs and more. It’s a total soup of life.”

He said even the plant life is complex, with each plant having a preferred salinity, soil type and area of the marsh.

“There is eelgrass in the deeper water that supports a lot of wildlife and a lot of fish,” Peugh said.

“We have the densest strand of eelgrass in the region and it’s basically a nursery for all of the fisheries,” Handa said. She explained that the eelgrass is also home to numerous invertebrates, and many birds directly consume the plant.

With tours and activities happening year-round, Kendall Frost Marsh already attracts a large number of bird watchers, nature enthusiasts, photographers, researchers and more.

The Kendall Frost Marsh in Mission Bay.
(Regina Elling)

Part of the De Anza Cove plan is to increase the amount of wetlands; Audubon officials said they believe this also will increase tourism and passive recreation.

“If you engineer a new, expanded marsh, you can engineer trails, boardwalks and recreation into it,” Peugh said.

Passive recreation also takes the form of fishing; in the early days of the park, Peugh said both hunting and fishing were common.

With the eelgrass acting a fish nursery, Handa said many of the fish in Mission Bay originate from the marsh, and whether people just enjoy watching the fish or like to eat them “it’s all connected.”

Even the mud underfoot at the marsh is important. According to recent studies, the top meter of mud in the marsh contains about 1,052 metric tons of carbon, part of the natural carbon sequestration marshes are known for.

The definition of carbon sequestration varies, from storing carbon in a carbon pool to the process of capturing and storing atmospheric carbon dioxide. Whichever way it is defined, it can help to slow down the accumulation of greenhouse gases and help reduce harmful effects of climate change.

As researchers and scientists have continued to study carbon sequestration, wetlands have become even more important than previously believed.

They have the ability to not only lower carbon emissions, but take in more emissions than they release, according to numerous research studies.

“Coastal wetlands can be seven times more effective than rainforests at sequestering carbon. And much of the research on carbon sequestration has been done at Kendall Frost Marsh and Mission Bay,” Peugh said.

The City’s Climate Action Plan has a target of restoring 700 acres of salt marshland, as well as other tidal wetland and riparian habitats, by 2035. Increasing the wetlands at Mission Bay Park would contribute significantly to meeting that target.

Increasing the amount of wetland would obviously increase the amount of carbon sequestration.

Along with carbon sequestration, sea level rise is also frequently toted as a benefit of having marshes. Researchers have also learned that wetlands can play a major role in keeping shorelines from eroding, which helps protect against potential sea level rising.

However, Peugh said Kendall Frost Marsh shoreline is eroding about one meter a year — and nothing is being done about it.

One solution would be to ensure the water from nearby Rose Creek is connected to the marsh.

“Rose Creek is a source of fresh water during the rain, and wetlands need seasonal fresh water,” he said, adding that area of the bay “has really dreadful water quality.”

He said not only does fresh water help the marsh, but the seasonal sediments that go along with it helps with normal shoreline erosion and potential sea level rise.

“The job of wetlands is to absorb all of that water and protect the inland. Since Mission Bay is so heavily urbanized, we want to be resilient in situations with access amounts of water, if we are trying to account for sea level rise,” Handa said.

She pointed out that “climate change is happening and happening rapidly,” and “We should be planning now for what is going to happen in the future.”

The most recent meeting of the City of San Diego Planning Department concerning De Anza Natural was held on April 20, at a the meeting of the Parks and Recreation Board.

De Anza Natural proposes amendments to the Mission Bay Park Master Plan to reimagine, repurpose and revitalize De Anza Cove in the northeast corner of Mission Bay Park.

The plan amendment recognizes the benefits of wetlands, which reduce the impacts of sea level rise and improve water quality.

Once the amended plan is adopted, implementation will be led by the Parks and Recreation Department.

Great blue herons and pintail ducks are both frequent visitors to local wetland areas.
(Roy Little / San Diego Audubon)

Officials from the City of San Diego have stated their support for expanding the current wetlands.

“One of the primary goals of the De Anza Natural Plan amendment is to identify wetland restoration areas, which will contribute significantly to meeting CAP wetland restoration targets, increase Mission Bay’s resilience to the impacts of climate change, provide critical habitat for sensitive species and create passive recreation and educational opportunities,” according to the city’s website at

As more information about wetlands comes to the forefront, the public appears to be acknowledging their importance.

“More than 71 organizations support ReWild Mission Bay,” Peugh said. “It’s just a tiny bit of the biodiversity problem, but it’s so important.”

With the future of De Anza Cove now seemingly taking shape, the hope is that the area can continue to serve a wide range of diverse uses, while protecting endangered species and rare plants.

“If you are paying attention to the science coming out things do not look good right now,” Handa said. “I wish more people would understand how dire the situation is. We need every single wetland we can possibly save at this point.”