Global Significance of Mangrove Blue Carbon in Climate Change Mitigation

Abstract

Mangrove forests store and sequester large area-specific quantities of blue carbon (Corg). Except for tundra and peatlands, mangroves store more Corg per unit area than any other ecosystem. Mean mangrove Corg stock is 738.9 Mg Corg ha−1 and mean global stock is 6.17 Pg Corg, which equates to only 0.4–7% of terrestrial ecosystem Corg stocks but 17% of total tropical marine Corg stocks. Per unit area, mangroves sequester 179.6 g Corg m−2a−1 and globally about 15 Tg Corg a−1. Mangroves sequester only 4% (range 1.3–8%) of Corg sequestered by terrestrial ecosystems, indicating that mangroves are a minor contributor to global C storage and sequestration. CO2 emissions from mangrove losses equate to 0.036 Pg CO2-equivalents a−1 based on rates of C sequestration but 0.088 Pg CO2-equivalents a−1 based on complete destruction for conversion to aquaculture and agriculture. Mangrove CO2 emissions account for only 0.2% of total global CO2 emissions but 18% of CO2 emissions from the tropical coastal ocean. Despite significant data limitations, the role of mangrove ecosystems in climate change mitigation is small at the global scale but more significant in the tropical coastal ocean and effective at the national and regional scale, especially in areas with high rates of deforestation and destruction.

Carbon Balance in Salt Marsh and Mangrove Ecosystems: A Global Synthesis

“…Median values are in parentheses and in Figure 1. Mangrove data from [6]. Salt marsh g dry weight (DW) biomass was converted to g C ORG using percent C ORG content in roots + rhizomes (41.5 ± 1.2%) and shoots (38.5 ± 0.7%) of various species [7][8][9][10][11][12][13][14][15].…”

“…Rates of C ORG burial in salt marsh soils are greater than rates in mangrove soils (Table 3), although the differences are not significant (one-way ANOVA on ranks, p > 0.05). There are wide variations in burial rates among locations, depending on a variety of factors, such as geomorphology, intertidal position, climate, extent of terrestrial and marine input, habitat age, species composition and soil texture [4,6]. Along with seagrasses, salt marshes and mangrove forests sequester more organic carbon on a per area basis than all other terrestrial and marine ecosystems (see Table 3 in reference [6]).…”

“…Salt marshes and mangrove forests are carbon-rich ecosystems that are perceived to play a role in climate regulation, biogeochemical cycling, and in capturing and preserving large amounts of carbon that counterbalance anthropogenic CO2 emissions [4][5][6]. It is unclear to what extent both ecosystems constitute a significant carbon sink in the global coastal ocean, and whether restoring and replanting new marshes and mangroves will assist in ameliorating climate change.…”

Nitrogen Cycling and Mass Balance in the World’s Mangrove Forests

“…Mean (±1 standard error, SE) and median total nitrogen (TN) concentrations (as percentage of dry weight, DW) of various above-and belowground mangrove components, including soils to a depth of 1 m. The mean C/N ratios (g/g) are as follows: soil C/N = 11.3; live wood C/N = 130.4; belowground root C/N = 80.9; litter C/N = 79.4. The C/N values for biomass were calculated based on relative percentage of biomass DW in the respective components (i.e., stems + branches for wood estimate) and dead and live root and rhizome DW for belowground estimates using the carbon data and references in [39]. N data from [4,[9][10][11] and earlier references within.…”

Carbon Balance in Salt Marsh and Mangrove Ecosystems: A Global Synthesis

“…Salt marshes and mangrove forests are carbon-rich ecosystems that are perceived to play a role in climate regulation, biogeochemical cycling, and capturing and preserving large amounts of carbon to help counterbalance anthropogenic CO2 emissions [4][5][6]. It is unclear to what extent both ecosystems constitute a significant carbon sink in the global coastal ocean, and whether restoring and replanting new marshes and mangroves will assist in ameliorating climate change.…”