Shoring Up Seal Beach
by Paulina Jenney, Institute of the Environment
First day of sediment spraying on Seal Beach National Wildlife Refuge. Credit: R. Nye, USFWS
On a crisp morning in Orange County, California, a giant hose took sediment from the bottom of Anaheim Bay and shot it over Seal Beach National Wildlife Refuge in a wide arc.
The new sediment, added in layers, raised the entire elevation of the shore in an innovative project to restore lush wetland plants, habitat for endangered wildlife, and foraging sites for birds that otherwise would be lost to climate change and sea-level rise.
The process, called thin-layer salt marsh sediment augmentation, is “one of the first examples in California of truly testing a climate change adaptation strategy on the ground,” said Karen Thorne, principal investigator on the project and a research ecologist for the U.S. Geological Survey.
With support from the Southwest Climate Science Center, which is headquartered at the University of Arizona’s Institute of the Environment, the researchers studied eight salt marshes along the California coast to understand how climate change and sea-level rise will affect coastal wetlands.
“What we found was that under most projections, all marsh habitats will be under water by 2080,” Thorne said. As global average temperatures continue to climb, polar glaciers melt and that additional water, once bound as ice, causes the sea level to rise.
“Of the eight sites we studied, we were able to determine that Seal Beach was the most vulnerable,” Thorne said. “It wasn’t even keeping up with current rates of sea-level rise.”
That is bad news for the birders and others who enjoy touring the 965-acre refuge and for the wildlife that relies on the salt marsh for survival. Salt marshes, or wetlands, are habitats that are routinely flooded by the ocean tides but are also influenced by dry inland conditions. Because they lie at the edge of two distinct climates, the marshes are home to a variety of animals, many of which are already threatened or endangered, like the California least tern and light-footed Ridgway’s rail.
Sediment sprayer with egrets on the shore of Seal Beach.Credit: R. Nye, USFWS
“In some places, over 90 percent of salt marshes have already been lost to human developments,” Thorne said. “If you’re a migratory bird, you’re now looking for little patches of green along the coast.” Seal Beach National Wildlife Refuge provides vital habitat for these birds, as well as other endangered species like the Eastern Pacific green sea turtle. It also provides a sea of benefits to its human neighbors.
“Salt marshes improve water quality, help with flood protection, absorb storm surges, and sequester carbon,” Thorne said. “They’re a good thing to have around your city. People like to kayak, hike, birdwatch, and fish in these areas. They’re really concerned about what will happen to them.”
Less than a year after the project began, the team brought the results of their study to the U.S. Fish and Wildlife Service, which was already looking for innovative ways to protect the marshes.
“They took the information and ran with it,” Thorne said, “We sat around a table and generated a list of strategies we could implement in the near and long term. We learned that Anaheim Bay was already being dredged, so instead of dumping the sediment in the middle of the ocean, we decided to use it.”
Between October 2015 and January 2016, the U.S. Fish and Wildlife Service sprayed sediment over 10 acres of Seal Beach, raising the elevation of the shore by 10 inches. The success of the first phase of the project helped Thorne and her team secure funding to continue monitoring the site for the next five years to better understand if the strategy worked.
“It’s a learning process,” Thorne added. “It’s a combination of doing good, relevant science, and having ready and engaged decision makers. As scientists, we want people to use the science we produce.”