64 / 112
64
they provide a larger carbon sink than mangroves which se-
quester 1.39 x10
-3
GtC/ha/year (Duarte
et al
., 2005). However,
they are also considerable sources of methane, but over a long
time period (~500 years) remain a greenhouse gas sink (Whit-
ing and Chanton, 2001).
Seagrass meadows are particularly good carbon sinks, as the
leaves last much longer than other marine biomass such as
phytoplankton (Duarte
et al
., 2005) and because they deposit
carbon into the ocean soil, resulting in long-term sequestration
(Romero
et al
., 1994).
The greatest oceanic absorption of CO
2
occurs in cold waters
or in areas with high organic matter (Barry and Chorley, 1998).
The carbon cycle in the oceans is influenced by physical and
biological processes (Reid, 2009). Global ocean services
2
may
be worth about USD 23 trillion a year, only slightly less than
the world’s GNP (GESAMP, 2001) and therefore maintaining
healthy ecosystems is economically important. There is also
evidence that healthy functioning marine ecosystems are nec-
essary to enable the continued marine sequestration of carbon
from the atmosphere (e.g. EC 2009; Herr and Galland 2009;
Laffoley and Grimsditch 2009).
Climate change is in itself a driver of ecosystem degradation
and affects carbon sequestration and storage. Climate change
impacts on ecosystems and on mitigation efforts should be
taken into account during restoration activities to ensure long-
Overall benefit-cost ratio
5.69
5.22
4.65
Costs
(of establishment and extraction)
3.45
2.51
1.82
Benefits
(direct – marketable products; indirect –
avoidedmaintenance cost of sea dyke system)
19.66
13.12
8.47
Discount rate
3
6
10
Table 1:
Costs and benefits of direct and indirect use values of mangrove restoration (adapted from Tri
et al
. 1998)
2 Services include provisioning (e.g. fish and minerals), regulating (e.g.
role in climate), supporting (e.g. role in water cycle) and cultural (e.g. tour-
ism, recreation)
Mangrove planting in Indonesia 2008–2009 © Sahabat Alam
Present value, million Vietnam Dong/ha