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Improve coastal resiliency: Conserve and create blue carbon sinks
Adaptation Strategies and Actions
Improve coastal resiliency: Conserve and create blue carbon sinks
Demonstrate to communities how creating and protecting blue carbon sinks can prevent greenhouse gas emissions and mitigate climate change.
The term “Blue Carbon” refers to the carbon that marine systems capture and store during natural processes. Carbon is trapped and stored (called sequestration) by marine systems in two main ways. First, plants take in carbon dioxide (CO2) from the atmosphere to grow (a process called “fixation” or “uptake”). Secondly, sediments bury and trap carbon that is in dead organic matter (such as leaves and roots) in an anaerobic (without oxygen) environment. Without oxygen, organic matter has a difficult time breaking down and carbon dioxide can not form. Salt marshes, mangroves and seagrasses are the main marine systems involved in carbon sequestration. While these three marine systems cover only a small percentage of the earth they are able to sequester more carbon than terrestrial systems, even more than rainforests which are more commonly known as major carbon sinks 7.
When marine systems are protected and well managed, they can perpetually capture carbon from the atmosphere and sequester it, thus mitigating global warming. Habitats that sequester and store blue carbon, like mangroves, salt marshes and seagrass beds, have been coined “carbon sinks” and their health and presence are critical for reducing further impacts of climate change. However, if these habitats are improperly managed, destroyed or developed, the concentrated buildup of carbon in marine systems is released into the atmosphere as the greenhouse gas carbon dioxide. Furthermore, carbon dioxide absorbed by water promotes ocean acidification.
Creating, protecting, and maintaining these marine habitats can provide a broad range of ecological and human benefits in addition to carbon sequestration for climate mitigation. These ecosystem services can include coastal storm defenses, recreational opportunities, sediment stabilization, and habitat quality improvements for a diversity of species, among others. While blue carbon is a relatively new area of research, there is enough information and resources available to help communities make informed and progressive decisions.
Conserve, Restore, and Nurture Current Carbon Sinks -Salt Marshes, Seagrass Beds, and Mangroves
Conserving existing carbon sinks is one the most affordable and proactive decisions a community can make for their coastal habitats. Many studies have tried to evaluate the amount of blue carbon that is lost from developing salt marshes, mangroves, and disturbing seagrass beds. One study estimated that 0.45Pg (billion tons) of blue carbon is released from the development and degradation of salt marshes, mangroves, and seagrasses, every year. This amount of carbon emission is equivalent to the United Kingdom’s annual fossil fuel carbon dioxide emission 1.
Restoring carbon sinks is another effective action that increases carbon sequestration and mitigates climate change. The Massachusetts Division of Ecological Restoration calculated the carbon sequestration benefits resulting from marsh restoration projects. In Hingham, two culverts were removed to restore tidal flow to 20 acres of salt marsh. This restoration promoted a net increase in carbon sequestration of 76 metric tons of CO2 per year. Additionally, 60 acres of salt marsh and grassland habitat was restored in Broad Meadows, Quincy by removing over four feet of wetland fill. This action generated a net increase in carbon sequestration of 101 metric tons of CO2 per year. The net increase in carbon sequestered in these restored wetlands through the year 2050 is estimated to be equal to the emissions from burning more than 800,000 gallons of gasoline between 2013 and 2050 10.
Nurturing the health of carbon sinks is important since a small change in their stability can result in a large emission of CO2. In addition to being carbon sinks, salt marshes and mangroves are natural coastal defense systems. Communities receive coastal protection and help mitigate climate change by conserving, restoring, and nurturing carbon sinks.
Create New Carbon Sinks by Choosing Living Shorelines For Coastal Restoration and Protection
Living shorelines are areas where native plants, sediment, fiber logs, stones and/or oyster reefs are organized along a shoreline. These natural structures to increase shoreline stabilization, expand habitat, and provide protection from shoreline erosion, storm surge, and wave impacts. Living shorelines take many forms such as a newly created salt marsh, cultivated oyster reef, or restored tidal area that was previously blocked. Unlike hard structures (e.g. bulkheads and seawalls) which are expensive, unnatural, and often detrimental to surrounding habitats and communities, living shorelines:
- Are relatively inexpensive 8
- Provide better protection during hurricanes 3
- Require minimal maintenance and repair
- Provide blue carbon benefits
In fact, per area, a newly created salt marsh sequesters more carbon than a fully mature salt marsh 4; seagrass beds undergoing restoration also accumulate and sequester carbon 5. Oyster reefs have another type of blue carbon benefit - they help offset ocean acidification by uptaking carbon from the water and fixating it in their growing shell as calcium carbonate. For every live kilogram (2.2 pounds) of oyster grown in the Atlantic Ocean, 114 grams (approximately ⅓ pound) of carbon is removed from the water 6.
These examples showcase just a few of the immediate and long term advantages of creating and fostering living shorelines instead of hard structures.
Learn More About Blue Carbon and Carbon Sinks
Salt marshes, seagrass beds, and mangroves provide multiple ecosystem and human benefits by serving as habitat for fish and wildlife, as protection against storms and sea level rise, as well as serving as carbon sinks. This blue carbon benefit is an important reason for local communities to make the economical and environmental choice of using living shorelines as a form of protection from climate change events and as mitigation for global warming. The salt marsh habitat is a dynamic and resilient environment that can be quickly destroyed yet, if the right actions take place, easily rejuvenated. The Massachusetts Division of Ecological Restoration has shown that developed coastal areas and areas where tidal access has been blocked, can be restored to salt marsh habitats. Additionally, the Division of Marine Fisheries is taking several initiatives to help protect and restore eelgrass beds in Massachusetts. Coastal areas can also be revitalized when private property owners, organizations and communities learn about blue carbon and collaborate with their local and state organizations to create and restore their carbon sinks.
Target Species, Species Groups, Habitats and Stressors
1. Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, et al. (2012) Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems. PLoS ONE 7(9): e43542. doi: 10.1371/journal.pone.0043542
2. Donato DC, Kauffman JB, Murdiyarso D, Kurnianto S, Stidham M, et al. (2011) Mangroves among the most carbon-rich forests in the tropics. Nature Geoscience 4: 293–297. doi: 10.1038/ngeo1123
3. Gittman RK, Popowich AM, Bruno JF, Peterson CH. Marshes with and without sills protect estuarine shorelines from erosion better than bulkheads during a category 1 hurricane. Ocean Coast Manage. 2014; 102: 94–102. doi: 10.1016/j.ocecoaman.2014.09.016
4. Davis JL, Currin CA, O’Brien C, Raffenburg C, Davis A (2015) Living Shorelines: Coastal Resilience with a Blue Carbon Benefit. PLoS ONE 10(11): e0142595. doi:10.1371/journal.pone.0142595 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0142595
5. Greiner JT, McGlathery KJ, Gunnell J, McKee BA (2013) Seagrass Restoration Enhances “Blue Carbon” Sequestration in Coastal Waters. PLoS ONE 8(8): e72469. doi: 10.1371/journal.pone.0072469
6. Mitra, A., & Zaman, S. (2015). Blue Carbon in Faunal Community. In Blue Carbon Reservoir of the Blue Planet (pp. 203-226). Springer India.
7. McLeod, E., G.L. Chmura, S. Bouillon, R. Salm, M. Bjork, C.M. Duarte, C.E. Lovelock, W.H. Schlesinger, and B.R. Silliman, 2011: A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2. Frontiers in Ecology and the Environment, 9 (10), 552–560. DOI: 10.1890/110004
8. Titus, J.G., K.E. Anderson, K.R. Cahoon, D.B. Gesch, S.K. Gill, B.T. Gutierrez, E.R. Thieler, and S.J. Williams, 2009: Coastal Sensitivity to Sea-Level Rise: A focus on the Mid-Atlantic region. U.S. Climate Change Science Program, Synthesis and Assessment Product 4.1, 320 p.
9. National Oceanic and Atmospheric Administration (2012) Eelgrass-Habitat of the Month. October 22, 2012
10. Division of Ecological Restoration (2014) Estimates of Ecosystem Service Values from Ecological Restroation Projects in Massachusetts, Summary of Report Findings. January 2014. Accessed January 2, 2017. http://www.mass.gov/eea/docs/dfg/der/pdf/eco-services-summary-ma-der.pdf
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