Blue Carbon and Coastal Ecosystems
How Blue Carbon can play a role in restoring our coastal parks.
What is Blue Carbon?
NOAA Climate.gov graphic adapted from original by Sarah Battle, NOAA Pacific Marine Environmental Laboratory.
Blue carbon refers to organic carbon that is stored by ocean and coastal ecosystems from the deep ocean to tidal marshes. This can be in the form of coastal vegetation, micro and macro organisms, carbon absorbed by ocean water, or stored in benthic sediments and soils.
When plants grow, they uptake atmospheric CO2 which is then stored in the leaves. Carbon is also stored in the soils through internal transport via root systems or through decaying organic matter. While this represents an important method of carbon sequestration, the largest amount of organic carbon found in the ocean is dissolved in sea water.
How is Blue Carbon Measured?
Scientists locate mangrove plants within the marsh.
Blue carbon stores can be estimated by measuring above and below ground biomass. It can also be measured through soil cores. Carbon sequestration is measured as a rate of carbon uptake per year whereas carbon storage is measured as a total weight of stored carbon.
Measuring blue carbon in vegetated areas such as salt marshes or mangrove forests can involve a variety of techniques, such as, leaf litter traps, measuring plant growth, and leaf area index measurements.
How are Parks Measuring Blue Carbon?
In 2019, 5 coastal parks in the Southeast Region measured the amount of soil organic carbon (SOC) sequestered by their mangrove forests using the spatial modeling methods outlined in Sanderman et al. 2018 . Then using these SOC measurements, they calculated the equivalent CO2 emissions from cars or coal fired plants using the EPA greenhouse gas equivalencies calculator to create the graphic below.
Figures from the Mangrove Soil Carbon Capture Brief for Everglades National Park.
Herring River Restoration Project
The Herring River Restoration (HRR) is a first in the nation project to incorporate blue carbon offsets into tidal marsh restoration.
Map of the Herring River showing the Herring River Basin highlighted in light turquoise and the Herring River in darker blue.
Next Steps for the HRR Project
Scientists collect soil samples and transfer them into plastic bags to be tested in the lab.
Moving forward, the HRR project team will work to measure methane emissions from low salinity areas, finalize soil carbon and methane measurements and techniques, and begin construction on the new tidal gates. There will also be a focus on creating models projecting water levels and soil accretion in unrestored and restored areas. The HRR team, including the National Park Service, USGS, USFWS, the Town of Wellfleet, and the Friends of the Herring River are working to further the knowledge of tidal marsh carbon sequestration and advance carbon storage measurement techniques to help future projects.
Looking Forward
Degraded tidal marshes can be found throughout coastal areas and represent a key area for future projects. In addition to the many ecosystem services they provide, these ecosystems present the opportunity for coastal parks to increase carbon sequestration within their bounds - and possibly participate in the carbon market, they also provide parks with the chance to reduce methane emissions from degraded habitats.
Further research into blue carbon sequestration, management of blue carbon ecosystems, and tools for measuring blue carbon storage is critical. The creation of standard practices for blue carbon projects and participation in the carbon offset market will be beneficial to future projects.
Resources
Mangrove carbon sequestration fact sheets for: Big Cypress National Preserve, Biscayne National Park, Cape Canaveral National Seashore, Everglades National Park, and Virgin Islands National Park.
