A Blue Carbon Primer
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A Blue Carbon Primer

The State of Coastal Wetland Carbon Science, Practice and Policy

Lisamarie Windham-Myers, Stephen Crooks, Tiffany G. Troxler, Lisamarie Windham-Myers, Stephen Crooks, Tiffany G. Troxler

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eBook - ePub

A Blue Carbon Primer

The State of Coastal Wetland Carbon Science, Practice and Policy

Lisamarie Windham-Myers, Stephen Crooks, Tiffany G. Troxler, Lisamarie Windham-Myers, Stephen Crooks, Tiffany G. Troxler

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About This Book

Key features:

  • Captures the historic context and recent developments in science and policy arenas that address the potential for coastal wetlands to be considered as significant contributors to carbon sequestration
  • Links multiple levels of science (biogeochemistry, geomorphology, paleoclimate, etc.) with blue carbon concepts (science, policy, mapping, operationalization, economics) in a single compendium
  • Concludes with a discussion of future directions which covers integrated scientific approaches, impending threats and specific gaps in current knowledge
  • Includes 7case studies from across the globe that demonstrate the benefits and challengesof blue carbon accounting
  • Written by over 100 leading global blue carbon experts in science and policy.

Blue Carbon has emerged as a term that represents the distinctive carbon stocks and fluxes into or out of coastal wetlands such as marshes, mangroves, and seagrasses. The Blue Carbon concept has rapidly developed in science literature and is highly relevant politically, as nations and markets are developing blue carbon monitoring and management tools and policies. This book is a comprehensive and current compendium of the state of the science, the state of maps and mapping protocols, and the state of policy incentives (including economic valuation of blue carbon), with additional sections on operationalizing blue carbon projects and 7 case studies with global relevance.

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Defining Blue Carbon

The Emergence of a Climate Context for Coastal Carbon Dynamics
Stephen Crooks
Silvestrum Climate Associates, LLC
Lisamarie Windham-Myers
U.S. Geological Survey
Tiffany G. Troxler
Florida International University
1.1 The Global Climate Challenge
1.2 The Emergence of Blue Carbon
1.3 Defining BCEs in the Context of Climate Resilience
1.4 What Are the Scale of Emissions and Removals by BCEs?
1.5 Advancing Blue Carbon Interventions
1.6 Conclusion


  1. Blue Carbon Ecosystems (BCEs) are defined as coastal wetland ecosystems with manageable and atmospherically significant carbon stocks and fluxes.
  2. Policy and management opportunities have promoted the emergence of blue carbon as a concept and spurred scientific interest to reduce uncertainties in coastal carbon budgets.
  3. The four major BCEs are generally classified by their plant communities: tidal marshes, tidal freshwater forests, mangroves, and seagrass meadows.


Global atmospheric carbon dioxide levels are now consistently above 400 ppm, well beyond levels occurring over the past 800,000 years (Lewis and Maslin, 2015). This rise is driven by human activities. In centuries prior to the 20th, land-use change altered carbon stocks through deforestation and soil degradation, but by the 1920s, fossil fuel emissions became the dominant source of increased atmospheric CO2 concentrations (Lal et al., 2012; Lewis and Marlin, 2015; Le Quéré et al., 2016). These emissions, on top of natural fluctuations, are taken up across the atmosphere, oceans, and biosphere at timescales measured from hours to millennia, and over longer timescales with the lithosphere.
Detailed in the Global Carbon Budget 2016 report (Le Quéré et al., 2016), it is estimated that over the last decade emissions due to fossil fuel burning and land-use change totaled 9.3 ± 0.5 and 1.0 ± 0.5 GtC year−1, respectively. About half of these annual emissions remain in the atmosphere (4.5 ± 0.1 GtC year−1), with significant sinks of carbon partitioned across ocean (2.6 ± 0.5 GtC year−1) and land (3.1 ± 0.9 GtC year−1) ecosystems.
Rising CO2 levels in the atmosphere are a principle driver of climate change (USGCRP, 2017). Globally annual averaged surface air temperature has increased by 1.8ºF (1.0ºC) over the past 115Áyears (1901–2016). This period is now the warmest in the history of modern civilization, with recent years repeatedly breaking records. Rising temperatures also drive the risk of significant unanticipated changes in the Earth’s system. At least two types of potential surprises exist: compounded impacts of simultaneous or sequential extreme climate events; and critical thresholds or tipping points, whereby a physical threshold is crossed in the climate system driving large and potentially irreversible impacts over human timescales (USGCRP, 2017). Positive feedbacks (self-reinforcing) have the potential to accelerate climate changes by tripping the Earth’s systems into new regimes that are very different from those experienced by current inhabitants of this very crowded world. The list of candidate tipping elements is long and includes: changes to atmospheric-ocean circulations (e.g., disruption to Atlantic Ocean Convection), cryosphere (e.g., accelerated melting of ice sheets), and carbon cycle (e.g., carbon dioxide and methane emission from boreal peatlands). Feedback to earth system warming include associated responses of the hydrosphere, including sea level rise and coastal flooding, changes in rainfall/storm patterns and intensity, and warming and acidification of ocean waters.
Reducing anthropogenic greenhouse gas (GHG) emissions by transitioning energy systems from fossil-fuel dominance is necessary to stabilize atmospheric climate forcing (IDDRI, 2015). Yet, while progress is being made in developing energy alternatives for a growing and increasingly resource-intensive population, globally we have done little to reduce our overall climate impact. With this backdrop, much more can be done to improve the management of the biosphere, recovering terrestrial and ocean sinks as a form of natural climate mitigation (Lal et al., 2012; Lal, 2016; Arneth et al., 2017; Griscom et al., 2017). Expanding our climate mitigation actions to more fully include the biosphere often involves benefits of improved social and environmental conditions despite the complexity associated with natural system fluctuations. Coastal ecosystems are an especially good example of where land-use management can lead to both natural climate mitigation and adaptation.


It is now 10Áyears since the term blue carbon emerged as a recognized concept, and one often associated with coastal carbon management. That is not to say the advent of blue carbon generated the first coastal wetland carbon budgets, or that this was even the first time that coastal wetland carbon cycling had been linked to climate change. That is far from the case (e.g., Twilley et al., 1992; Chmura et al., 2003; Duarte et al., 2005). But as a concept, recognizing the opportunity that improved management of certain coastal settings—blue carbon ecosystems (BCEs)—might contribute to a climate response, it captured the imagination of the international policy and conservation community working on climate mitigation and adaptation. For example, likening millions of small tidal wetland losses to a million little fires illustrates the climate mitigation potential of coastal management (sensu Kroeger, 2017). Blue carbon as a concept, and thus BCE management as one natural climate solution, has thus arisen at a moment in time when connecting the biosphere to climate mitigation actions is gaining traction within international policy discussions. In Textbox 1, we describe the maturing appreciation of BCE management as a climate mitigation tool.


In the context of climate policy frameworks, blue carbon has been taken to represent the carbon accumulating in vegetated, tidally influenced coastal ecosystems such as tidal forests (including mangroves), tidal marshes, and intertidal to subtidal seagrass meadows (International Blue Carbon Science Working Group, 2015). Climate-relevant blue carbon pools and fluxes include physical, chemical, and biological exchanges within and between sediments and soils, waters, living biomass and non-living biomass, as well as GHG exchanges with the atmosphere.
Occupying less than 2% of ocean area (or <5% of global land area) vegetated coastal ecosystems are estimated to be responsible for nearly 50% of carbon burial in marine sediments (Duarte, 2005). This represents a very high concentration of carbon flux from atmosphere and surface waters to long-term sediment storage. More significantly, destruction of these same ecosystems results in fluxes of historical carbon pools back to the atmosphere as carbon dioxide, from soil and biomass stocks that had accumulated over hundreds to thousands of years (Pendleton et al., 2012).
Such a focus on only tidal forests, tidal marshes, and seagrasses reflects perhaps a first step to inclusion of other carbon sequestering, transferring and storing ecosystems in the future. This first step is pragmatic in that it provides for a limited but important set of marine and ocean systems to be evaluated and integrated with developing land-based climate mitigation frameworks under the UNFCCC (Howard et al, 2017; Sutton-Greer and Howard, 2018). By focusing on these three vegetated ecosystems; however, we may be failing to fully recognize the climate benefits of improved management other coastal and marine ecosystems (e.g., kelp, microalgae, macroalgae, and fish) that are part of the biosphere’s process of capturing, fixing, and transferring carbon dioxide to long-term storage of sediment or deep ocean water bodies (Smale et al., 2018).
For the purpose of practicality, recognition as a BCE—specifically one that focuses on connecting management of coastal ecosystems to climate policies and finance opportunities associated with land-ownership—requires that the following conditions be met:
Recognition of blue carbon as a concept of climate policy interest stems back to reports by the IUCN (International Union for Conservation of Nature) and UNEP (United Nations Environment Programme) (Laffoley and Grimsditch, 2009; Nellemann et al., 2009). Occurring against a backdrop of developing international policies for terrestrial forestland management and consideration of peatland soils, these reports invigorated the discussion of coastal and marine ecosystems within the global carbon cycle. The focus of both of these studies is to raise awareness that healthy coastal and marine ecosystems contribute to the removal of carbon from the atmosphere and long-term storage, and also that these ecosystems are threatened and degraded by human actions.
At the same time, foundations and the California Climate Action Reserve (CCAR) were exploring whether tidal wetlands restoration would be a valid inclusion in the carbon market as an offsets mechanism. What emerged was a perspective from the carbon management and project development side (Crooks et al., 2009). This review highlighted that while natural and restoring tidal wetlands do sequester carbon and continuously build soil carbon stocks, these were not the most significant fluxes of relevance to near-term climate mitigation and carbon project development. Rather, the more significant fluxes were driven by destruction of intertidal wetlands with conversion of soils from wet and anoxic to dry and oxic conditions, or with remobilization of soils through excavation or erosion. Carbon dioxide emissions from drained organic soils may continue for decades after the disturbance until either the stock is exhausted or the soils are no longer maintained dry (Deverel and Leighton, 2010). Akin to terrestrial peatlands, avoiding emissions, which were occurring at scale around the world, were the most significant near-term climate mitigation opportunity. The study also highlighted the need for coordinated science to improve quantification of drivers, fluxes, and long-term storage potential.
What might have seemed the end of the story at that point was met as a challenge and an opportunity by the conservation community (Chapter 2). In the United States, Restore America’s Estuaries have been engaged, establishing a Blue Ribbon Panel consisting of the CCAR project team leads, wetland scientists, carbon market, and legal experts to map out a 5-year workplan. This resulted in White House and Federal agency support for science programs, landscape scale project assessments, and the production of methodologies that linked restoration and conservation of tidal marshes, mangroves, and seagrasses to the voluntary carbon markets under the Verified Carbon Standard (Emmer et al., 2015; Emmer et al., 2018a,b). At the global level, Conservation International, IUCN, and UN Intergovernmental Oceanographic Commission launched the Blue Carbon Initiative (BCI) to connect and empower scientists and policy analysts/makers to build capacity around the world and engage with decision makers in senior levels of government at key venues, such as the annual climate change negotiations. The word from the policy community was that they were now curious about coastal and marine ecosystems (remaining uncertain about the term blue carbon) but needed to see demonstration that the science was sound, that interventions could be enacted and that the benefits could be scaled to have meaningful impacts both to benefit local livelihoods and have a positive impact on GHG emission reductions.
An early success came at UNFCCC COP 16 (United Nations Framework Convention on Climate Change, Conference of the Parties 16), in Cancun, just prior to the official launch of the BCI. Here a side event was held outlining the early findings of three coordinated reports: a World Bank-funded study that estimated the scale of carbon emissions from a dozen converted large coastal wetland systems from around the world (Crooks et al., 2011); an economic analysis funded by the Linden Trust for Conservation that highlighted the potential to apply carbon finance for blue carbon interventions in developing countries (Murray et al., 2011); and, a policy analysis, also funded by Linden, that clarified that blue carbon could be incorporated under existing land-use focused international policy agreements (Climate Focus, 2011). The side event generated some buzz around blue carbon, demonstrating a pathway for inclusion for coastal and marine ecosystems into a policy context (https://blogs.worldbank.org/climatechange/category/tags/blue-carbon). A particular success of the side event was the subsequent inclusion of coastal wetlands within guidance for national reporting GHG emissions and removals with land-use change involving wetlands (IPCC, 2014).
At the time of publishing this book, there has been a rapid expansion in the number of scientific, economic, and policy publications on blue carbon. Demonstration projects (such as the GEF, Global Environment Facility Blue Forest Project) and networks (e.g., International Blue Carbon Partnership) are being funded to explore scaling of interventions and facilities are being created to support financing (e.g., Blue Natural Capital Financing Facility).
  1. Rates of carbon sequestration and/ or prevention of emissions of GHGs by the ecosystem is cumulatively at sufficient scales to influence climate;
  2. Major carbon stocks, change in stock and fluxes of GHGs can be quantified spatially and temporally;
  3. Anthropogenic drivers are impacting carbon storage, stock change, or GHG emissions;
  4. Management of the ecosystem to improve sequestration or emission reductions is possible and practicable;
  5. Interventions can be achieved without causing social or environmental harm; and
  6. Management actions can be aligned with existing or developing international policy and national commitments to address climate change.
Those ecosystems currently recognized as BCEs meet these...

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