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Restoring Wetlands While Storing Carbon in the Delta

April 2014

The protection, restoration, and enhancement of the Delta ecosystem, one of California’s coequal goals, is no easy task, especially with tight government funding. That’s why land managers are tasked with determining which projects will result in resilient ecosystems and ensure those dollars are spent wisely.

“There is a lot of time and money going into these restoration projects and we don’t want to say ‘Well, jeez, I wish that had worked out,’” said Dr. Judith Drexler, a wetland ecologist and research hydrologist with the U.S. Geological Survey’s California Water Science Center in Sacramento. “We want to go in with our eyes open and say ‘Here are our best ideas on what could work.’”

Dr. Drexler, whose research includes studies in California’s Delta and South Carolina’s Lower Waccamaw River, believes it’s important for managers and decision-makers to understand wetland formation processes and use these as guiding principles to ensure successful restoration of individual sites and the broader Delta landscape. She offered her knowledge based on experience and suggestions for moving forward during an April 4 Delta Science Program Brown Bag seminar entitled Applying New Science to Restoring Wetlands and Storing Carbon in the San Francisco Estuary.

Her presentation focused on the formation of peat, an organic turf composed of partially decayed plant matter, through a process known as vertical accretion.

“Vertical accretion is the deposition of stuff that can be organic in nature, or it can be inorganic like sediment washing in from the watershed,” said Dr. Drexler. “Those two processes, which are always occurring, build up the marsh surface and help the area keep pace with sea level rise.”

This “stuff” also plays the important role of stabilizing carbon and keeping it from returning to the atmosphere as a greenhouse gas. In her study at the Lower Waccamaw River in eastern South Carolina, Dr. Drexler and her colleagues say a better understanding of wetland processes “would enable managers to reap the potential benefits of a developing carbon reduction market, which could provide much-needed funds for refuges in exchange for enhancing and restoring marsh habitat for the purpose of carbon sequestration.”

Managing a wetland was also included in Dr. Drexler’s discussion, in particular how best available science can inform decisions relating to habitat restoration.

“We now better understand the processes of wetland and marsh management so that we don’t have to guess,” said Dr. Drexler. “The information can better help us to come up with places where wetland restorations can be successful and sustainable over the long haul.”

Another portion of her presentation covered paleosalinity, the study of historic freshwater-salt water dynamics, in the Delta, an area long considered mainly a freshwater system. The research allowed Dr. Drexler and her colleagues to understand how rare spikes of salinity over the past 6,000 years might have affected, among other things, the phenomenon of vertical accretion of peat and its subsequent carbon sequestration. For instance, she says her research indicates that while fresher parts of the Delta tend to be more productive at sequestering carbon, they also have higher rates of greenhouse gas emissions such as methane.

“In the very salty areas, there are very little methane emissions, which is causing some to say ‘If we’re going to restore marshes, let’s just restore salt marshes because we can store carbon and we don’t have to worry about high methane emissions, which might end up cancelling out the greenhouse gas benefit since methane is a very potent greenhouse gas,’” said Dr. Drexler. “So, one of the things we need to learn more about is in these freshwater habitats is there a variation – and what causes the variation in the methane – and is there a way we can manage it so that methane is not a significant emission?”

Meanwhile, the Department of Water Resources (DWR) has been conducting similar research in the Delta, specifically on Twitchell Island and Mayberry Farms, an area of Sherman Island. The studies have included restoration projects, greenhouse gas emission sampling, and carbon sequestration projects.

DWR’s engineers have been focusing on creating the most efficient and productive balance of habitat restoration that keeps the emission of greenhouse gases to a minimum while sequestering carbon in peat.

“The ultimate outcome of the restoration project will be hundreds of additional acres of freshwater emergent wetlands,” states DWR’s project information flyers. To view some background materials on their research, please click here.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)