Environmental Engineering Reference
In-Depth Information
average, coastal
salt marshes
store 362
which biodiversity is being lost (Mora and
Sale
2011
). The marine, coastal and estuarine
ecosystems sustaining awide spectrumof
-
2,012 tonnes of CO
2
e/ha (Chmura et al.
2003
).
3. Seagrasses store from 66 to 1,478 tonnes of
CO
2
e/ha, which is mostly sequestered in the
soils of seagrass beds (Mateo et al.
1997
;
Vichkovitten and Holmer
2005
; Gordon
et al.
2011
).
4. Table
8.1
re
ora and
fauna are no exceptions to this rule. Despite their
enormous socio-economic value and ecosystem
services, estuarine and coastal ecosystems are
some of the most heavily used and threatened
natural systems globally (Lotze et al.
2006
; Worm
et al.
2006
; Halpern et al.
2008
). Their deteriora-
tion due to human activities is intense and
increasing and has been the subject of a number of
studies during recent years. Researches on this
vertical depict that 50 % of salt marshes, 35 % of
mangroves and 29 % of seagrasses have been
either lost or degraded worldwide over the last
50
fl
ects the standing carbon stock in
the plant biomass and soil under the domain
of blue carbon, and the
fl
gures are compared
with other forest types of the planet.
8.1.2 Threats
100 years (Valiela et al.
2001
; MEA
2005
;
Orth et al.
2006
; UNEP
2006
; FAO
2007
; Waycott
et al.
2009
). Causes of habitat conversion vary
globally, but can be largely traced to human
development pressures. They include conversion
to aquaculture, agriculture, forest overexploita-
tion, industrial use, upstream dams, dredging,
eutrophication of overlying waters, urban devel-
opment and conversion to open water due to
accelerated
The present century is the age of human population
explosion whose chain reactions are urbanization,
industrialization, unplanned change of land use,
exploitation of living and non-living resources and
several other activities that threaten the existence
of human civilization. Expected scenarios of
human population growth and consumption levels
indicate that cumulative human demands will
impose an unsustainable toll on Earth
-
s ecological
resources and services accelerating the rate at
'
sea
level
rise
and subsidence
Table 8.1
Comparison of carbon stocks and accumulation of carbon in soils in terrestrial and coastal ecosystems
Ecosystem type
Standing carbon
stock (gC/m
2
)
Total global
area
(*10
12
m
2
)
Global stocks
(*10
15
gC)
Soil carbon
accumulation
rate (gC/m
2
/year)
Plants
Soil
Plants
Soil
Tropical forests
12,045
12,273
17.6
212
216
2.3
2.5
-
Temperate forests
5,673
9,615
10.40
59
100
1.4
-
12.0
Boreal forests
6,423
34,380
13.7
88
471
0.8
2.2
-
Tropical savanna and
grassland
2,933
11,733
22.5
66
264
-
Temperate grassland and
shrublands
720
23,600
12.5
09
295
2.2
Deserts
176
4,198
45.5
08
191
0.8
Tundra
632
12,737
9.5
06
121
0.2
5.7
-
Croplands
188
8,000
16.0
03
128
-
Wetlands
4,286
72,857
3.5
15
225
20
Tidal salt marshes
Unknown
(0.22)
Mangroves
7,990
0.152
1.2
139
Seagrasses
184
7,000
0.3
0.06
2.1
83
Kelp forests
120
-
720
Na
0.02
-
0.4
0.009
-
0.02
Na
Na
Source Laffoley and Grimsditch (
2009
)
