Coastal Wetlands: Conservation of Blue Carbon Ecosystems for Climate Change Mitigation and Adaptation (original) (raw)

The atmosphere and the ocean exchange gases resulting in an overall absorption of CO 2 in the ocean Burning fossil fuels, industry and changes in land uses (deforestation, landfill , fires and/or agriculture), and respiration by humans and animals releases extra CO 2 and CH 4 to the atmosphere Plants within terrestrial forests, tidal marsh, mangrove and seagrass ecosystems sequester CO 2 through photosynthesis, which accumulates in their biomass and soils CO 2 , CH 4 CO 2 , CH 4 CO 2 CO 2 CO 2 CO 2 CO 2 CO 2 CO 2 CO 2 Photosynthesis by plankton in the ocean sequester Export of plant and macroalgal biomass in the deep ocean sequesters CO 2 FIGURE 28.1 Conceptual diagram of carbon sequestration by blue carbon ecosystems and some of the activities that influence CO 2 exchange among the atmosphere, soil, and ocean in coastal areas and the open ocean. The major global C pools include the atmosphere, oceans, fossil fuels, vegetation, soils, and detritus. Landfill, smokestacks, cattle farming, and other human activities result in additional methane (CH 4) emissions. 28. CONSERVATION OF BLUE CARBON ECOSYSTEMS FOR CLIMATE CHANGE 966 VII. COASTAL WETLAND SUSTAINABILITY seagrass ecosystems occupying less than 0.2% of the seabed area, they contribute nearly 50% of the CO 2 sequestration in marine sediments, and their C sequestration rates exceed those in the soils of many terrestrial ecosystems by 30-to 50-fold (Chmura et al., 2003; Duarte et al. 2005, 2013; Mcleod et al., 2011). Most macroalgal communities grow on rocky substrate and do not form significant in situ sedimentary C deposits, but the initial estimates of the amount of macroalgae C sequestered in sediments and deep-sea waters suggest that it is comparable to the C sequestered by all other BC ecosystems combined (Krause-Jensen and Duarte, 2016). Furthermore, the C captured by BC ecosystems is stored in marine soils for millennia, rather than the decades or centuries typical of terrestrial forests. This is due in part to the high rates of vertical accretion in tidal marsh, mangrove, and seagrass ecosystems, ranging from 0.4 to 21 mm year À1 (Mateo et al., 1997; McKee et al., 2007; Duarte et al., 2013). This process of raising the seafloor is driven partly through the trapping and settling of particles from the water column and partly through organic matter production. This acts to bury the C in anoxic conditions, thereby slowing down its remineralization by microbes (Krauss et al., 2014; Mateo et al., 2006; Pedersen et al., 2011). Globally, tidal marsh, mangrove, and seagrass ecosystems sequester annually a similar amount of C to terrestrial forests, despite their extent being less than 3% of that of forests (Duarte et al., 2013). Unlike terrestrial forests, mangroves and tidal marshes rarely burn in wildfires, although they are exposed to other disturbances (e.g., tropical storms). BC ecosystems provide important and valuable ecosystem services critical for climate change mitigation and adaptation, including coastal protection from storms and shoreline erosion, regulation of water quality, provision of habitat for commercially important fisheries and enhancing biodiversity, and being globally significant C sinks (