This paper is a product of Frontiers in Ecology and the Environment.


Highlights:

  • Coastal wetlands sequester substantial amounts of carbon, mostly in soils
  • Interest in the climate benefits of coastal wetlands has drawn attention to how other components of marine ecosystems might play a role in climate mitigation
  • Coral reefs, kelp, and marine fauna, while important components of carbon cycling in the ocean, are not involved in long-term carbon sequestration
  • Due to jurisdictional issues, practical management of coral, phytoplankton, kelp, and marine fauna within climate mitigation frameworks would be difficult
  • Current climate mitigation efforts in the coastal and marine realm should focus primarily on coastal wetlands, as they represent long-term carbon sinks and potential carbon sources upon conversion, and can be managed for their carbon sequestration value

Abstract: The international scientific community is increasingly recognizing the role of natural systems in climate-change mitigation. While forests have historically been the primary focus of such efforts, coastal wetlands – particularly seagrasses, tidal marshes, and mangroves – are now considered important and effective long-term carbon sinks. However, some members of the coastal and marine policy and management community have been interested in expanding climate mitigation strategies to include other components within coastal and marine systems, such as coral reefs, phytoplankton, kelp forests, and marine fauna. We analyze the scientific evidence regarding whether these marine ecosystems and ecosystem components are viable long-term carbon sinks and whether they can be managed for climate mitigation. Our findings could assist decision makers and conservation practitioners in identifying which components of coastal and marine ecosystems should be prioritized in current climate mitigation strategies and policies.

Within the context of climate-change mitigation, enhancing the capacity and role of natural carbon sinks has become an increasingly important scientific and political topic (note: for definitions of selected terms used throughout the main text see WebTable 1). Research on natural carbon sinks has focused primarily on oceans (Sabine et al. 2004) and terrestrial forests (Houghton et al. 1990), and most recently, on coastal systems (Mcleod et al. 2011). The ocean represents the largest active carbon sink on Earth, absorbing 20–35% of anthropogenic CO2 emissions (Khatiwala et al. 2009). However, management strategies to enhance oceanic carbon sequestration and storage are currently impractical, and there is strong concern about the ecological impacts of such interventions (Russell et al. 2012; Committee on Geoengineering Climate 2015). Therefore, scientists and decision makers now focus on terrestrial and coastal ecosystems, which show high potential for climate mitigation and lend themselves to local and national management strategies.

For example, the United Nations Framework Convention on Climate Change (UNFCCC) recognizes that terrestrial forests sequester large amounts of carbon in their biomass, and under the Convention, forests are the basis of climate mitigation strategies such as Reducing Emissions from Deforestation and Forest Degradation (REDD+). Similarly, coastal wetlands (mangroves, tidal marshes, and seagrasses) are increasingly acknowledged as important carbon sinks, based on their ability to sequester large amounts of carbon in their biomass and, more importantly, in their soil (Hiraishi et al. 2014). The carbon sequestered in coastal and marine vegetated ecosystems is known as “coastal wetland blue carbon”. On a per area basis, coastal wetlands are more efficient carbon sinks than most terrestrial forests (Mcleod et al. 2011; Pan et al. 2011). Anthropogenic conversion and degradation of coastal wetlands can lead to major emissions, because much of the carbon stored in the soils is released back into the atmosphere and ocean (Pendleton et al. 2012; Kauffman et al. 2014), shifting the wetlands from net sinks to sources of carbon. The conservation, restoration, and sustainable use of these ecosystems are therefore essential to ensuring that the carbon sequestration benefits are maintained, along with the many additional ecosystem services they provide (eg fisheries, coastal protection).

With the increasing recognition of the importance of coastal wetlands for climate mitigation, decision makers have expressed greater interest in the climate mitigation potential of other coastal and marine ecosystems and ecosystem components, particularly kelp, coral, phytoplankton, and marine fauna (WebFigure 1; Chung et al. 2013; Lutz and Martin 2014). While all of these components provide valuable services and have important conservation value, not all of them are suitable for consideration in climate-change policy frameworks. In this paper, we synthesize the state of the science and compare the long-term carbon sequestration ability of various coastal and marine systems to clarify which components should be prioritized in climate mitigation efforts….”

Read on and access the full paper at: Ecological Society of America.