The $ 63 million wetland restoration could be a model for how California is adapting to climate change. But it takes forever


An ambitious intertidal wetland restoration project on nearly 1,200 acres of Delta farmland has just completed its first phase, and the hoped-for transformation is already flourishing: river otters, rare seabirds and a single black bear have all returned to a once empty place. pasture called Dutch Slough – promising results for similar efforts toward many California environmental goals, including greenhouse gas storage.

In the town of Oakley in Contra Costa County, the restored wetlands of Dutch Slough are bordered by subdivisions and dairy farms, with Mount Diablo towering in the distance. When complete, the $ 63 million restoration will be the largest of its kind in California, creating habitat for endangered salmon and other wildlife as part of a plan explaining how the state can become more resilient to climate change.

The state’s water resources department, which runs the Dutch Slough Tidal Marsh Restoration Project, hopes this will be a model for many more restorations, with the goal of restoring 30,000 acres of the 360,000 acres of wetlands in origin of the long-lost Sacramento-San Joaquin River Delta. to farms and housing.

At a time when global targets for reducing greenhouse gas emissions are not being met, scientists are looking for ways to adapt to global warming; restoring wetlands in the San Francisco Bay Area and the sprawling Delta holds a key strategy. Wetlands reduce destruction from flooding caused by storms and sea level rise, and can also recharge drought-starved aquifers as they gradually hold and release water.

They also play a key role in the absorption of carbon from the atmosphere and its long-term storage.

“You can put carbon in forests, where it can be burned,” said Dennis Baldocchi, professor in the department of environmental science, policy and management at UC Berkeley. “But if you put it in wet areas, it can stay on for a very long time. The limitation is that we have a limited area of ​​land that we can convert.

The wetlands can be seen at Dutch Sough with Mount Diablo in the background near Oakley, where the wetlands are the subject of a state-funded project to restore its habitat and various ecosystems.

Brontë Wittpenn / The Chronicle

Baldocchi is one of many scientists now using Dutch Slough to study carbon sequestration in coastal freshwater marshes. Last week he was joined in the field by US Geological Survey ecologist Scott Jones, who is conducting similar research.

Jones staggered through the wetlands in waders, holding up a cuboid plastic container large enough to hold the towering tule plants. He demonstrated how the container can be used to trap gases and then be hooked up to a greenhouse gas analyzer that measures the amount of methane and carbon dioxide emitted or sequestered by this square foot of swamp.

“Finding these ecosystems capable of storing carbon over the long term helps us meet our greenhouse gas reduction goals,” said Karen Thorne, research ecologist for the US Geological Survey.

Restoration began in 2018, when excavators dug the loamy soil to create canals that mimic natural tidal areas. Conservation groups have planted an assortment of native plants and trees and given them time to take root before the dikes are broken this fall. Today, more than half of the old pastures have been converted into a labyrinth of curving streams under a vast expanse of yellow-tipped tule.

The catch is the slowness of the entire project: the remaining restoration is not expected to be completed until around 2025, more than two decades after the property was purchased in 2003. Many observers are worried about the weather. it takes to overcome the bureaucratic steps to make such projects come true.

“It’s the same licensing process as a housing development, even though we’re creating better habitat than before,” said Molly Ferrell, senior environmental scientist in the Department of Water Resources at the ‘State.

Especially with the role of wetlands as a natural barrier to sea level rise, it is important for the state to act quickly, said Dylan Chapple, senior environmental scientist at the Delta Stewardship Council, which administers the grants. for Baldocchi’s research.

“Every year counts,” said Chapple. “Wetlands are truly critical natural infrastructure. The sooner they can sink into the ground, the longer they can persist. Without intervention, the delta is expected to experience full-scale flooding by 2100, he said.

US Geological Survey ecologist Scott Jones and biology technician McKenna Bristow measure carbon dioxide and methane emissions from wetlands in Dutch Slough in Oakley.

US Geological Survey ecologist Scott Jones and biology technician McKenna Bristow measure carbon dioxide and methane emissions from wetlands in Dutch Slough in Oakley.

Brontëë Wittpenn / The Chronicle

John Cain has been involved with Dutch Slough from the start. He first discovered the property in 1998, while on staff for the State Water Resources Department. He worked with landowners and the City of Oakley to negotiate the state’s purchase of $ 28 million for three plots originally intended to be converted into housing.

“It’s very difficult to find places in the delta that you can restore to tidal marshes,” he said.

Cain said 98% of the delta was reclaimed for agriculture by the end of the 19th century, first to support the gold rush and then economic growth. With the help of Chinese workers, the settlers drained the wetlands and built small dikes to keep water out. Over time, the ground sagged, sometimes sinking up to 20 feet.

Such a depth is too shallow for wetland restoration because the plants would be completely covered when the tides rise, said Cain, who is now director of conservation at River Partners, the nonprofit responsible for planting plants. natives on the site.

Dutch Slough hadn’t sunk as much as other areas, as it sits at the mouth of Marsh Creek, which drains the east side of Mount Diablo and “carries mineral soils, sand and clay to on the edge of the delta for millennia, ”Cain said.

Marsh Creek is also part of the salmon migration route between the San Joaquin and Sacramento rivers and the ocean. Now that the new Dutch Slough Marsh is open to the creek, young salmon can stop, rest and fatten up, giving them a better chance of surviving the trip. It will also provide nursery habitat for other types of fish.

Dutch Slough is also right across from where UC Berkeley’s Baldocchi grew up. His father’s farm was located where a patch of beige stucco houses stands today.

“At the time, the soils were rich. The land was very productive, ”he said. “It’s just not sustainable over hundreds of years of continuous subsidence and soil loss. “

Baldocchi and his lab use devices that measure gas flows as well as a number of variations, from water salinity and temperature to wind direction and speed, to study how much wetlands absorb water. methane and carbon dioxide, and how much they release. The peaty soil produced in intertidal wetlands can remain stable for several thousand years.

“We want permanent carbon sinks,” he said. “For me, wetlands are the best.

Tara Duggan is a writer for the San Francisco Chronicle. Email: [email protected] Twitter: @taraduggan


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