NOAA’s Office of National Marine Sanctuaries has released a two-part Conservation Science Series: Blue Carbon in Marine Protected Areas. These reports describe how blue carbon ecosystems help mitigate climate change by sequestering and storing atmospheric carbon.
Blue carbon ecosystems mitigate climate change by removing carbon dioxide from the atmosphere and transporting it into sediments or deep waters, where it can remain indefinitely if undisturbed. Accounting for these processes, and how they can help to achieve global carbon mitigation and emission reduction goals, is an emerging area of focus for marine protected area management.
Led by Greater Farallones National Marine Sanctuary, with support from the Greater Farallones Association, Part 1 of a series seeks to inform and guide MPA managers in the assessment, protection, and management of blue carbon habitats and processes. Part 2 of this series, focuses on a case study for Greater Farallones National Marine Sanctuary.
Among the findings:
“This is the first assessment of multiple blue carbon sequestration processes in a U.S. federal MPA, with the primary purpose of informing one of the nation’s largest MPAs in its management decision-making. The carbon storage and annual sequestration for two coastal blue carbon habitats, seagrass and salt marsh, and two oceanic carbon sequestration processes, kelp export and dead whale falls, were assessed within the boundaries of the sanctuary using regional and site-specific data. These processes have the potential to sequester 4,950 megagrams of carbon (MgC) each year (or 18,150 metric tons CO2 equivalent), which is valued at $925,650 in societal benefit annually and is 140 times the amount of CO2 that is emitted from annual site operations. Whale falls account for roughly 60% of this annual sequestration; salt marsh, seagrass, and kelp account for roughly equal parts of the remaining 40%, though annual sequestration by the region’s kelp forests have declined by 99.7% from 2008 to 2019. Sanctuary coastal blue carbon habitats currently hold approximately 175,000 MgC in their sediments, which, if destroyed, could release approximately 643,000 metric tons of CO2, or the equivalent of adding 140,000 vehicles to the road for one year.”
Pathways for carbon sequestration by seagrass, salt marsh, and mangroves. Carbon is captured by the absorption of dissolved inorganic CO2 and fixation of carbon into the plant tissues, and sequestration into woody biomass and sediments. Image source: Clarifying the role of coastal and marine systems in climate mitigation, Howard, J et al, Frontiers in Ecology and the Environment (2017).