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59
ECOSYSTEM RESTORATION
FOR CLIMATE CHANGE
MITIGATION
Much recent attention has been given to the potential of eco-
systems, especially forests, to take up (sequester) additional
carbon and hence mitigate climate change. Unfortunately, this
process is disrupted when natural ecosystems are converted for
agricultural use. This releases much of the carbon stored in
plants and soil, and also alters the physical and biological ef-
fects of the landscape on the climate (Bala
et al
., 2007).
Some of these effects warm the climate, whilst others cool it.
The high albedo (reflectivity) of grassland and deserts plays a
role in atmospheric cooling (Hansen
et al
., 1998; Thompson,
1998). High rates of evapotranspiration (release of water into
the atmosphere) from tropical forest reduce surface air tem-
perature and increase rainfall (Bonan, 2008). The structure of
vegetation also influences the regional climate: for example, a
study in Australia found that land cover change (mainly defor-
1 To illustrate how substantial these ecosystem stores of carbon are, the
global annual emissions of carbon dioxide from human activity in 2004
totalled 38 Gigatonnes (IPCC 2007).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. tourism, recreation)
All living matter (biomass) – from grasses and trees to salt marshes and plankton
–
stores carbon. Terrestrial biomass carbon stores are often referred to as “green carbon”.
Worldwide, terrestrial vegetation, soil and detritus currently store 2261 Gigatonnes of
carbon (GtC; IPCC, 2007)
1
. Approximately half of terrestrial biomass carbon stocks
are found in forest (IPCC, 2007). The oceans and coastal vegetation also store a large
amount of carbon (often known as “blue carbon”), which is thought to be approxi-
mately 38334 GtC (IPCC, 2007), though there is uncertainty about the precise quantity
(Nellemann
et al
., 2009).
estation) explained up to 50% of the observed warming and
changes to rainfall patterns due to reduced surface roughness
(Pitman
et al
., 2004).
The marine environment also has a key role in climate regula-
tion. The oceans store and conduct heat, while ocean chem-
istry is important in regulating carbon uptake (IPCC, 2007;
Reid
et al
., 2009).
Restoration of terrestrial and marine ecosystems therefore
protects and enhances the climate regulating services of eco-
systems as well as the carbon stocks that aid climate change
mitigation.
Many ecosystems are currently carbon sinks (they store more
carbon than they lose). The IPCC Fourth Assessment (AR4)
Report suggests that the size of the terrestrial sink is approxi-
mately 0.5–1.5 GtC per year while the marine sink is approxi-
mately 1.8–2.6 GtC per year (IPCC, 2007). However, land use
change and degradation damage the terrestrial sink as well as
generating carbon emissions (Ong, 1993; Anser
et al
., 2005;
Eliasch, 2008; Lal, 2008).