large carbon sink capacity of some specific vegetated coastal habitats. Indeed,
the maximum reported carbon sink capacity of salt-marsh, mangrove and sea-
grass ecosystems (Table 1) exceeds by over 10, 6 and 2 fold that of undisturbed
Amazonian forest, estimated at 1.02 t C ha
-1
(Grace et al., 1993). For instance,
carbon burial by salt marshes, which cover a small area of the conterminous
USA, has been estimated to account for 21% of the total carbon sink of all USA
ecosystems (Bridgham et al., 2006). Hence, an upper estimate of the carbon
capture capacity of blue carbon sinks can be derived by combining maximum
estimates of the area covered globally with upper estimates of the carbon bur-
ied per unit area (Table 1). These calculations yield an upper estimate for the
carbon capture capacity of blue carbon sinks at 329 Tg C year
–1
, accounting for
71% of the burial of organic carbon in the ocean (Table 1).
Table 1. Mean and maximum (in brackets) estimates of the area covered by blue
carbon sinks and the annual organic carbon burial rates. Carbon burial rates are
presented per hectare (mean,range and , the upper confidence limit of the mean
of individual ecosystem estimates, in brackets) and globally (as reported ranges
of mean rates of global carbon burial derived using different methods and, in
brackets, an upper estimate derived using the maximum area and the upper con-
fidence limit of the mean burial rate). The data is for vegetated coastal areas and
their percentage contribution to carbon burial in the coastal and global ocean (in
brackets the burial rate and percentage contribution of vegetated habitats calcu-
lated from the upper estimates). Total burial rates of organic carbon in estuarine
and shelf sediments and deep-sea sediments are provided for comparison. Data
derived from reviews by Cebrián and Duarte (1996), Duarte et al. (2005a), and
Bouillon et al. (2008).
Component Area Organic Carbon burial
Million km
2
Ton C ha
-1
y
-1
Tg C y
-1
Vegetated habitats
Mangroves 0.17 (0.3) 1.39, 0.20 – 6.54 (1.89) 17 – 23.6 (57)
Salt Marsh 0.4 (0.8) 1.51, 0.18 – 17.3 (2.37) 60.4 – 70 (190)
Seagrass 0.33 (0.6) 0.83, 0.56 – 1.82 (1.37) 27.4 – 44 (82)
Total vegetated habitats 0.9 (1.7) 1.23, 0.18 – 17.3 (1.93) 114 – 131 (329)
Depositional areas
Estuaries 1.8 0.5 81.0
Shelf 26.6 0.2 45.2
Total depositional areas 126.2
Total coastal burial 237.6 (454)
% vegetated habitats 46.89 (0.72)
Deep sea burial 330.0 0.00018 6.0
Total oceanic burial 243.62 (460)
% vegetated habitats 45.73 (0.71)
37
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