Tidewater Blue Carbon
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Blue Carbon Revival

The Putrid Smell of Carbon Sequestration

I spent my childhood summers on the banks of the Rappahannock River in the tidewater region of Virginia. Close to the cottage we rented each year was a dank area called Coleman’s Swamp. It held the allure of adventure for young boys and proved a fertile location for various forms of mischief. Still imprinted in my memory is the putrid, sulfurous smell of rotting organic matter rising from the mud and grasses as we tromped along the edges of the swamp. Climate change and global warming were not yet emerging concepts, and thoughts of mass extinction existed only in the annals of geology. Only now, many years later, do I understand that the noxious smell of Coleman’s Swamp was the smell of blue carbon.

The physical color of carbon is not blue, and the term “blue carbon” refers to the vast stores of carbon removed annually from the atmosphere and sequestered in our coastal marine ecosystems. These ecosystems are incredibly efficient at capturing atmospheric carbon and storing it for hundreds of thousands or even millions of years. Because of their effectiveness in storing carbon, coastal ecosystems play a critical role in mitigating the environmental damage caused by burning fossil fuels. Mangrove swamps, coastal and estuarine grasslands, and salt marshes are examples of blue carbon ecosystems that lock away carbon.

In the past decade, we started appreciating the role these ecosystems play in the biosphere’s carbon cycle. But their future role in fighting climate change is uncertain and depends on whether we decide to preserve or destroy these fragile coastal ecosystems.

The Wetlands

Coastal wetlands account for only two percent of the earth’s ocean surface, but they capture more than 50 percent of the carbon absorbed by the oceans each year. Once captured, the carbon is efficiently sequestered in the wetland sediments. Wetlands are 10 to 100 times more efficient at carbon sequestration than inland forests.

The key to their success is found in wet, muddy, clay-rich soils where water doesn’t readily circulate and oxygen depletion is common. Without sufficient oxygen, bacteria can’t complete their job of digesting plant and animal remains and returning the organic carbon to the atmosphere as carbon dioxide and methane. Instead, the carbon remains stored in the soils.

Part of the elegance of wetlands is their dynamic adaptation to a changing environment. As sea levels rise and ocean waters creep inland, the wetlands keep pace and continue their role as carbon sinks and a sustainable habitat for many species.

The wetlands act as a damper on the build-up of greenhouse gases and global warming. They can’t completely stop the rising levels of CO2 in our atmosphere, but they can slow down the process.

The fact that wetlands organically build and keep pace with sea-level rise is critical. As the marshes grow, they thicken, and the volume of carbon in long-term storage grows. But, the success of these dynamic ecosystems depends on their conservation and protection.

Ecosystems in Need of Protection

Overdevelopment adjacent to our wetlands for commercial and agricultural projects creates significant damage. Dikes and other structures, built for the control of water flow, alter the hydrodynamics of the ecosystem and make it less effective. Likewise, too much agricultural runoff into the wetlands leads to damaging nitrogen pollution and a loss of efficiency. Most egregiously, the infill of marshes to create new land permanently destroys wetland areas.

Pessimistic assessments of climate change sometimes overlook the things humans can do to protect the earth’s environment during a period of rapid climate change. Conserving, protecting, and restoring wetland habitats is a positive step within reach of local, state, and federal governments. It is also a step within reach of individuals who are looking for positive solutions.

A blue carbon revival should be a part of our emerging efforts to mold the planet’s future. Some experts predict that developing and cultivating blue carbon sinks could eventually let them remove up to 15 percent of the world’s carbon emissions.

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What is Blue Carbon? (Source: National Marine Sanctuary Foundation)

Wetlands will keep up with sea level rise to offset climate change ( Emily Greenhalgh)

These Hidden Carbon Sinks May Prove Crucial for Our Survival (by Karen McVeigh; Mother Jones)

‘Dangerous blindspot’: why overlooking blue carbon could sink us (by Karen McVeigh; The Guardian)

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.