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Carbon Storage and Sequestration science
Blue Carbon Estuary Assessments

Carbon Stored and Sequestered by Coastal Wetlands

Carbon is held in the above and below ground plant matter and within wetland soils. As plants grow, carbon accumulates annually and is held within soils for centuries. Science is increasing our understanding of how much carbon is sequestered (captured from the atmosphere via photosynthesis) and stored by wetlands.

Carbon Storage

The largest store of carbon in wetland habitats is in the soil. In the first meter of soil, they contain:

  • Seagrasses: 512 Mg CO2e/ha
  • Salt marsh: 917 Mg CO2e/ha
  • Mangroves: 1,028 Mg CO2e/ha 

 carbon storage graph oct2014

Carbon Sequestration

Wetland plants regularly remove CO2 from the atmosphere and sequester it in the form of soil carbon, where it can remain for centuries. Average carbon sequestration rates are several times greater than for forests:

  • Seagrasses: 138 ± 38 gC/m2/yr --> 5.1 tCO2/ha/yr
  • Salt marsh: 218 ± 24 gC/m2/yr --> 8.0 tCO2/ha/yr
  • Mangroves: 226 ± 39 gC/m2/yr --> 8.3 tCO2/ha/yr

 carbon sequestration graph oct2014v3


2Sources: Pendleton et al. 2012 and Pan et al. 2011.

3Source: McLeod et al. 2011.

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Blue Carbon Estuary Assessments


Blue Carbon in Galveston Bay, Texas

(August 2017)

This study compared carbon storage and capture in restored salt marshes versus natural salt marshes in Galveston Bay, Texas.

You can access the full report here


Tampa Bay Blue Carbon Assessment, Tampa, Florida

(June 2016)

The Tampa study assessed the climate mitigation potential of Tampa coastal habitat over the next 100 years and how sea-level rise will impact these habitats. The report also provides management recommendations for habitat adaptation.

The study found that Tampa coastal wetland habitats (including mangroves, salt marsh and seagrass) will remove over 73 million tons of CO2 from the atmosphere over the next 100 years. This is equivalent to taking 160,000 passenger cars off the road every year until 2100.

You can access the full report here

See the full press release


Coastal Blue Carbon Assessment for the Snohomish Estuary, Puget Sound, Washington
(Feb 2014)2013-05-28 13.45.29

The Snohomish Assessment took place in Puget Sound, WA and determined the climate mitigation benefits of estuary restoration. 

The study found that currently planned and in-construction restoration projects in the estuary will result in at least 2.55 million tons of CO2 sequestered from the atmosphere over the next 100 years. This is equivalent to the 1-year emissions for 500,000 passenger cars. If plans expanded to fully restore the Snohomish estuary, the sequestration potential jumps to 8.9 million tons of CO2, equal to the 1-year emissions of about 1.7 million passenger cars. 

This study was the first of its kind and provides much needed research for assessing carbon changes in wetland habitats and for determining wetland restoration potential to mitigation climate change. For more information:
Snohomish Press Release
Snohomish Blue Carbon Assessment - Executive Summary
Snohomish Blue Carbon Assessment - Full Report

This approach can be applied to other estuaries.

Partner Projects:

Waquoit Bay National Estuarine Research Reserve - Bringing Wetlands to Market

Conservation International - Blue Carbon Initiative - Scientific Working Group

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