Wetlands are supposed to be, well, wet.
But not too wet, or else the plants drown, endangered birds don’t have a place to nest and the marshes fail to protect coastal homes from storm surges.
It’s exactly what was happening at the Seal Beach Wildlife Refuge—at least until researchers from Cal State Long Beach and the U.S. Fish and Wildlife Service got involved with a new technique to raise the floor of the marsh.
Christine Whitcraft, director of CSULB’s Environmental Science and Policy program, said coastal wetlands are some of the most productive habitats in the world: they filter water run-off, provide a space for fish to breed and the plants absorb excess water as they provide a buffer from ocean storm surges.
“The challenge is, despite this importance, we’ve still lost a lot of wetlands from human interference,” Whitcraft said.
That human interference was highlighted in a 2013 study that showed the sea level rise rate in the Seal Beach marsh was three times higher than the national average, Whitcraft said. In addition to sea level rise, the marsh was getting deeper because natural rivers —now concrete channels—no longer regularly deposit mud into the marsh.
With the combination of rising water and eroding marsh floors, plants crucial to the wetlands ecosystem can’t get established and aren’t tall enough to let birds keep their nests during high tides, particularly the endangered light-footed Ridgeway’s rail.
To combat the drowning of the marsh, researchers sprayed dredged mud from the bottom of Huntington Harbor during the first half of 2016 to raise the marsh by 10-inches.
This was the first sediment augmentation study done in Southern California. It’s a relatively new technique, Whitcraft said, with a handful of studies conducted in the East and Gulf coasts and one recently in the San Francisco Bay Area.
Since the sediment spraying in 2016, the researchers have been waiting and monitoring the eight-acre site. Only recently have they started to see plants sprouting and invertebrates like earthworms coming back to the site.
“It is recovering at the rate we expected it to, but it wont be back to a marsh for a few years,” Whitcraft said.
The project is a possible solution to a small piece of a big issue, making the success even more exciting, she said.
“I think when people hear of sea level rise, it can seem daunting,” she said. “It’s nice to be engaged in the process of designing solutions for large scale environmental problems.”
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