West Coast
A drone view of the Gilbert Tract and Emerson Slough in Oakley, Calif., on Tuesday, August 1, 2023. More than half-way complete, the Dutch Slough Restoration Project will create a powerful carbon sink to combat climate change while also restoring wetlands to bring back native wildlife to the area. (Jane Tyska/Bay Area News Group)

CA - Restored Delta tidal marsh fights climate change and attracts wildlife, native species

Dutch Slough tidal freshwater marsh providing safe home for juvenile salmon and other fish

Once eyed for thousands of homes, the recently restored Dutch Slough tidal marsh in east Contra Costa County is already flourishing as a new habitat for fish and wildlife, a living laboratory for scientists and one of the world’s strongest sinks for absorbing and storing carbon long-term.

Led by the state Department of Water Resources, the ambitious $73 million project to restore 1,187 acres of freshwater Delta tidal wetlands near Oakley – one of the largest such projects in the state – is a little more than half finished. When it is completed, the scientists are hoping it will become a model for future restoration projects, climate change defenses and scientific research.

“It’s taking in carbon at a rate compared to the top 1 percentile (of all ecosystems) in the world (annually),” said Katie Bandy, the department’s Dutch Slough Tidal Marsh Restoration project manager. “It’s taking in a lot more carbon than other land is producing.”

That’s important, because many scientists believe that capturing and storing carbon dioxide is one of the more cost-effective ways to combat global warming. Simply put, too much carbon in the atmosphere causes temperatures to rise and acts like a blanket keeping in solar heat.

Dennis Baldocchi, professor at UC Berkeley’s Department of Environmental Science, Policy and Management, has studied the Oakley tidal marsh’s carbon-capture potential, along with its prospects for flooding prevention, for the past two years. He calls the restored tidal marsh “a living laboratory,” “a big, fancy petri dish.”

Coincidentally, the scientist grew up in Oakley across the street from what was then the Emerson Dairy and nearby farmland that would eventually be transformed into the Dutch Slough freshwater tidal marsh.

The reason these tidal wetlands are so productive, in part, is because of their long growing season, he said.

“We have plenty of water, plenty of sunshine, so really tall, dense vegetation can grow, and so that’s really good at capturing light for photosynthesis,” he said.

Since the wetlands are flooded, it’s hard for oxygen to get into the subsoils, so organic materials build up rather than decay and there’s less carbon emitting back out into the atmosphere, he explained.

Baldocchi is one of several scientists – including some at the U.S. Geological Survey – studying carbon capture at the site.

Some ways to store carbon, however, are only good up to a point, Baldocchi said, noting, for example, when forests burn, they release carbon dioxide back into the atmosphere.

“Wetlands can be very effective, large carbon sinks, but we don’t have a lot of area, there’s limited lines along the river,” he said. “On the other hand, grasslands and forests are much slower (at storing carbon), but we have hundreds of millions of acres that are available, so we have to almost use both. … We have taken advantage of the best ecosystem that’s appropriate for that landscape.”

Scientists estimate that more than 350,000 acres of tule marsh once blanketed the area from Sacramento to Stockton, yet only 2% to 5% of those are left. European settlers moved here in the Gold Rush days and many hired Chinese immigrants to divert the waters and build levees for farming.

Read more.