Blue Carbon and Its Value for Society

By Andrew Gray and Elizabeth Watson

“Blue carbon” is shorthand for the carbon found in three major coastal and marine ecosystems: mangroves, seagrasses, and salt marshes. On an acre-by-acre basis, coastal wetlands and seagrass beds assimilate more carbon per year than mature rain forests.

But rather than primarily storing carbon visibly as towering tree trunks, coastal environments build up carbon stores underground through root growth and through the trapping of sediment washed in with the tides. Blue carbon provides important benefits that should be considered in shoreline management.

Coastal marsh and seagrass bed (at low tide) at San Quintín Bay. Photo by Elizabeth Watson.

As efforts to mitigate the impacts of anthropogenic greenhouse gas emissions are on the rise, attention has been increasingly focused on the ability of coastal preservation and restoration projects to sequester carbon. For example, living shorelines, which use native vegetation and/or oyster reefs and other materials to protect shorelines from coastal erosion, are an alternative approach to shoreline management that provide carbon benefits.

Coastal restoration and enhancement projects, and green technologies like living shorelines, can help mitigate climate change through increased carbon sequestration, and generate other benefits to society such as providing critical habitat to fish, crustaceans, birds and marine mammals, improving water quality, and protecting coastal communities from storm surge.

New research conducted by CICESE, the University of California and allied researchers is focusing on carbon sequestration performed by eelgrass ecosystems in Baja California and gaining a better understanding of the greenhouse gas mitigation benefits of coastal conservation. 

Volcano marsh in San Quintin, Baja California. Photo by Elizabeth Watson.

One important area of focus for us is on the implications of changing climate to carbon sequestration in eelgrass beds. Eelgrass is at the most southern part of its range in Baja California and there is some evidence that warming conditions is causing its decline. What happens to carbon sequestered in sediments that are no longer stabilized by seagrass beds? Does it remain sequestered? Or is it reworked and mineralized back to atmospheric carbon dioxide? Our research team has also looked at carbon sequestration in Baja California wetlands and how changes in the extent of coastal wetlands in the state might influence carbon storage.

We have found that the wetlands in Baja California are highly pristine compared to coastal wetlands in the United States, and most other regions of Mexico. Our analysis of historical aerial photographs thus provides important insights into dynamic natural processes and coastal geomorphology. We plan to publish the results of this research in an academic journal soon.

Collection of sediment core samples. Photo by Elizabeth Watson.

This research represents a unique collaboration between scientists with CICESE and University of California researchers that is focused on coastal blue carbon, an emerging global nexus of environmental science, conservation, and policy.  Our goals are to expand understanding of carbon sequestration occurring in Baja California lagoons and to raise awareness of the greenhouse gas mitigation benefits of coastal habitats.

About the authors

  • Elizabeth Watson is assistant professor of environmental sciences and the Wetland Section Leader at the Patrick Center for Environmental Research at the Academy of Natural Sciences in Philadelphia, Pennsylvania. She lived in Ensenada and studied Baja California wetlands at CICESE from 2008 to 2009.
  • Andrew Gray is assistant professor of environmental sciences at the Environmental Sciences Department of the University of California Riverside.
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