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 Mitigating climate change through restoration of coastal ecosystems


  Date:
      May 30, 2023
  Source:
      Georgia Institute of Technology
  Summary:
      Researchers are proposing a novel pathway through which coastal
      ecosystem restoration can permanently capture carbon dioxide from
      the atmosphere.

      Seagrass and mangroves -- known as blue carbon ecosystems --
      naturally capture carbon through photosynthesis, which converts
      carbon dioxide into living tissue.


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FULL STORY
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One of the primary drivers of climate change is excess greenhouse gases
like carbon dioxide in the atmosphere. Mitigating climate change in
the coming century will require both decarbonization -- electrifying
the power grid or reducing fossil fuel-guzzling transportation -- and
removing already existing carbon dioxide from the atmosphere, a process
called carbon dioxide removal.

Researchers at the Georgia Institute of Technology and Yale University
are proposing a novel pathway through which coastal ecosystem restoration
can permanently capture carbon dioxide from the atmosphere. Seagrass and
mangroves -- known as blue carbon ecosystems -- naturally capture carbon
through photosynthesis, which converts carbon dioxide into living tissue.

"Mangroves and seagrasses extract carbon dioxide from the atmosphere all
day long and turn it into biomass," said Chris Reinhard, an associate
professor in the School of Earth and Atmospheric Sciences (EAS). "Some
of this biomass can get buried in sediments, and if it stays there,
then you've basically just removed carbon dioxide from the atmosphere."
Restoring these ecosystems could potentially benefit local flora and fauna
and help to energize coastal economies. But Reinhard and colleagues now
suggest that restoring them could also remove additional carbon through
a novel pathway while combating increasing acidity in the ocean.

In May, they presented their research in "Ocean Alkalinity Enhancement
Through Restoration of Blue Carbon Ecosystems" in Nature Sustainability.

Carbon 101 There are two major types of carbon that cycle through the
Earth system: organic carbon and inorganic carbon. Organic carbon is
contained in living matter, such as algae, plants, animals, and even
humans. This form of carbon can remove carbon dioxide from the atmosphere
temporarily, but if it becomes buried in sediments at the seafloor, it
can lead to permanent carbon dioxide removal. Inorganic carbon can also
be found in many forms, including rocks and minerals, but is present as
a significant dissolved component of ocean water.

Roughly 30% of the carbon emitted by human activities since the
industrial revolution is now stored as dissolved inorganic carbon in the
ocean. Although carbon dioxide stored as organic carbon can be disrupted,
effectively redistributing carbon dioxide back into the atmosphere, carbon
dioxide removal by inorganic carbon is potentially much more durable.

"Even if you change the way a coastal ecosystem restoration project is
operating, potentially remobilizing previously stored organic carbon,
inorganic carbon capture is largely a one-way street," said Mojtaba
Fakhraee, lead author of the study and former postdoctoral researcher
in EAS. "So even if a massive ecosystem disruption in the future
undoes organic carbon storage, the inorganic carbon that has been
captured will still be in the ocean permanently."  Capturing Carbon,
Counteracting Acidity Coastal ecosystems naturally remove carbon from the
atmosphere and provide a range of environmental and economic benefits to
coastal communities, but many human interventions have caused extensive
degradation or destruction of natural coastal environments. Planting
more mangroves and seagrasses, maintaining them, and protecting the
overall ecosystem can restore their functioning and lead to additional
carbon removal from the atmosphere. Reinvigorating coastal ecosystems as
a technique for mitigating carbon emissions is not a new idea, but past
research has focused on carbon removal through organic carbon burial and
has not explored the potential for carbon removal through the formation
of inorganic carbon.

Another major result of human fossil fuel use beyond climate change is
ocean acidification from carbon dioxide in the atmosphere dissolving in
the water and driving down the pH of the ocean, which can have severe,
negative impacts on many organisms like corals. Storing carbon dioxide
as inorganic carbon in the ocean could help mitigate this, because
the chemical processes that lead to carbon capture as inorganic carbon
involves alkalinizing ocean waters.

"The basic idea here is that you are shifting the acid-base balance
of the ocean to drive conversion of carbon dioxide in the atmosphere
to inorganic carbon in the ocean," Reinhard said. "This means that the
process can help to partially offset the negative ecological consequences
of ocean acidification."  Modeling Carbon Capture To explore how effective
restoring coastal ecosystems could be for inorganic carbon capture, the
researchers built a numerical model to represent the chemistry and physics
of sedimentary systems -- the complex mixture of solid particles, living
organisms, and seawater that accumulates at the seafloor. A key advance
of the model is that it specifically tracks the potential benefits of
restored mangrove or seagrass ecosystems and their impacts on organic
and inorganic carbon cycling. It also calculates the effects of other
greenhouse gases, such as methane, that can sometimes be created in the
process of restoring mangrove and seagrass ecosystems.

"This model comes up with representations for the rates of carbon
transformation in the sediment based on how much mangrove is growing
above the sediment," said Noah Planavsky, senior author on the study
and professor of Earth and planetary sciences at Yale. "We found that
across an extremely large range of scenarios, restoration of blue carbon
ecosystems leads to durable carbon dioxide removal as dissolved inorganic
carbon."  The team hopes this research could provide an impetus to protect
current coastal ecosystems and economically incentivize restoration of
degraded ecosystems, potentially as a new form of carbon offset.

"Companies that are trying to offset their own emissions could
potentially purchase carbon removal through funding restoration of coastal
ecosystems," Reinhard said. "This could help rebuild these ecosystems
and all of the environmental benefits they provide, while leading to
durable carbon dioxide removal from the atmosphere."
    * RELATED_TOPICS
          o Plants_&_Animals
                # Nature # Ecology_Research # Organic # Marine_Biology
          o Earth_&_Climate
                # Global_Warming # Air_Quality # Forest # Geochemistry
    * RELATED_TERMS
          o Carbon_dioxide o Carbon_dioxide_sink o Forest o Carbon_cycle
          o Carbon_monoxide o Ocean_acidification o Greenhouse_gas
          o Chloroplast

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Story Source: Materials provided by Georgia_Institute_of_Technology. Note:
Content may be edited for style and length.


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Journal Reference:
   1. Mojtaba Fakhraee, Noah J. Planavsky, Christopher T. Reinhard. Ocean
      alkalinity enhancement through restoration of blue carbon
      ecosystems.

      Nature Sustainability, 2023; DOI: 10.1038/s41893-023-01128-2
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Link to news story:
https://www.sciencedaily.com/releases/2023/05/230530174257.htm

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