Agriculture Reference
In-Depth Information
vegetation and the restoration of degraded
lands, all of which result in maintaining or
increasing SOC.
stocks. These two goals apply to the problem
at local (catchment) and global scales, and in
the short term as well as the longer term.
Climate
Interactions and Trade-offs
Between Services
Soils play a major role in the global carbon
cycle, the dynamics of which have a large
effect on Earth's climate system. Today, the
top
1
m of soil worldwide contains about
twice as much carbon in organic forms as
does the atmosphere, and three times as
much as does the vegetation (Batjes, 1996).
Over the past three centuries, land clearing
and land management for agriculture have
resulted in the acceleration of soil organic
matter decay and the transfer of more than
100
Pg carbon from the soil to the atmos-
phere as carbon dioxide (CO
2
) (Sabine
et al
.,
2004). In light of these facts, the goal is to
mitigate climate change by practices towards
ecosystem-level carbon sequestration includ-
ing increasing SOC.
The extraction of peat and its use
as fuel, litter or a soil improver has also
resulted in substantial transfers of CO
2
(>
20
Pg C) to the atmosphere over the same
period (Gasparatos
et al
., 2011; Leifeld
et al
.,
2011). Once in the atmosphere, CO
2
has a
long half-life and it functions as a powerful
heat-trapping gas that is the primary cause
of the global temperature increases (IPCC,
2007). These temperature increases, in turn,
accelerate SOC decay and create a self-
reinforcing feedback, with warming begetting
further warming (Heimann and Reichstein,
2008).
Practices that increase SOC, such as
mulching and reduced tillage, increase and
retain soil moisture, providing resilience to
in-season rain shortages (dry spells), which
are expected to occur more often in some re-
gions as a consequence of climate change.
The management of global soil carbon stocks
with best practices has the potential to in-
crease the magnitude of the SOC pool over
decadal timescales to help mitigate climate
change and climate variability. Two major
soil science and management challenges are
to: (i) minimize further losses of SOC to the
atmosphere; and (ii) increase the soil carbon
As illustrated above, there are many wide-
scale goals and short- and long-term actions
that must be implemented to meet growing
human demands for food, water, energy, cli-
mate change mitigation and biodiversity
in the coming decades at local and global
scales. Soil organic carbon is central to these
essential services and could be an import-
ant determinant of maintenance, buffering
and enhancement of the supply of many
ecosystem goods and other services under
changing socio-economic and environmen-
tal conditions, as implied by the interactions
ponent in ecosystem functioning, provides
a useful mechanism to address jointly the
threats to various ecosystem services. A focus
on SOC enables us to set out the interactions
between individual services and to assess ap-
propriate synergies associated with actions
to enhance SOC from local to global scales.
Actions affecting SOC long-term goals
will inevitably have interactions and feed-
backs. For example, as previously discussed,
one interaction is between SOC and cli-
mate. In this case, management that induces
SOC losses contributes to increasing green-
house gas concentrations in the atmosphere,
which in turn will increase air temperature
and create a feedback by accelerating SOC
decomposition and further losses (Heimann
and Reichstein, 2008). Actions focusing on
increasing the provision of one ecosystem
service individually often impact various
other ecosystems services negatively. We
must learn from the past, where a focus on
single services has led to significant re-
ductions in the supply of other services
(Tilman
et al
., 2006; Don
et al
., 2012). Typical
examples are the focus on agriculture in-
tensification for food production, which has
led to water pollution and losses of biodiver-
sity due to excess nutrients and pesticides
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