Climate Change and Soil Carbon Impacts - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 240

The C that humans are currently releasing
through fossil fuel use has been locked up
in the geosphere for hundreds of millions of
years, and was accumulated over many mil-
lions of years. Using the biosphere to cap-
ture this geospheric C does not add up - the
geospheric C released is too large for the
biosphere to store effectively. Given this
knowledge, reducing C emissions is obvi-
ously more important than attempting to se-
quester the C after it has been released.

has a large, cost-competitive mitigation
potential. Soil C sequestration can be use-
ful to meet short- to medium-term targets,
especially if these targets are large. In add-
ition to the mitigation potential, increasing
soil C stocks provides many co-benefits
in terms of soil fertility, workability, water-
holding capacity, nutrient cycling, reduced
emissions risk and a range of other positive
soil attributes (Lal, 2004). These arguments
for using C sequestration for climate miti-
gation need to be weighed against the limi-
tations discussed above; for example, time
limitation, non-permanence, displacement
and difficulties in verification. Despite
these limitations, soil C sequestration may
have a role in reducing the short-term at-
mospheric CO 2 concentration, thus buying
time to develop longer-term emissions re-
duction solutions across all sectors of the
economy.

Conclusions

There is still some uncertainty over future
responses of soils to climate change, but
most projections suggest that, globally, soils
either lose only small quantities of soil C or
soil C stocks may, in fact, increase. The global
picture, however, is underpinned by con-
siderable regional variation in response,
with the response determined by a com-
bination of factors, including opposite
impacts of increased temperature and de-
creased soil moisture on decomposition rates
and the balance between changes in C losses
from decomposition and C gains through
increased productivity.
In terms of using soils to mitigate cli-
mate change, soil C sequestration globally

Acknowledgements

This project contributes to SmartSoil (EU-
FP7-KBBE-2011- 5; Grant agreement num-
ber: 289694). This paper is an update of a
paper published by Smith (2012; Soils and
climate change. Current Opinion in Envir-
onmental Sustainability 4, 539-544).

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