Soil Carbon: a Critical Natural Resource – Wide-scale Goals, Urgent Actions - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 11

(Trumbore, 1997; Lal, 2003). Humans rely on
SOC stocks to help meet their needs for food,
water, climate and biodiversity on our planet
(Hooper et al ., 2000). Land degradation result-
ing in carbon losses is of great concern because
it threatens our capacity to meet the demands
of the world population, which is estimated
to grow to over 9 billion by 2050. The result-
ing increased demand for food, water and en-
ergy will put an increasingly heavy pressure
on land resources and the global climate.
Scientific research has given us clear and
compelling evidence that SOC stocks have
been reduced in many regions of the world,
with these reductions often associated with
agriculture and land degradation (Amundson,
2001; Sanderman and Baldock, 2010). One of
the grand challenges for society is to manage
soil carbon stocks to optimize the mix of five
essential services - provisioning of food, water
and energy; maintaining biodiversity and regu-
lating climate ( Fig. 2.1 ) . These essential services
and their interaction with SOC could be seen
in an Anthropocene perspective (Richter, 2007).
The global changes in SOC provide evidence
that human activities are indeed having a

global impact on the Earth system and on these
five essential services underpinned by SOC.
For this chapter, SOM reflects the range
of all organic materials found in the soil
profile that influence the physical (e.g. soil
bulk density, water infiltration rates), chem-
ical (e.g. pH, nutrients) and biological (e.g.
biomass, exogenous substrates) properties of
soils. In this context, SOC can be increased
by the addition of organic materials into the
soil profile by means of different management
for different purposes (Ingram and Fernandes,
2001; Swift, 2001).
Scientific research has helped develop
an understanding of both the general SOC
dynamics and characteristics and the influence
of soil management on SOC at different tem-
poral scales. This combined information can
be used to motivate new research efforts to
identify and promote best SOC management
practices at local management units and to
facilitate improvements at regional to global
scales. Moving forward, there is a need to
identify and overcome barriers to the adop-
tion of practices that enhance SOC. Here, we
argue for the necessity of an ambitious global

Food

Biodiversity

Species and functionality
maintenance

Increasing
production

Soil organic
carbon

Secure quality
and quantity

Increasing
production

Energy

Mitigation of
climate change

Climate

Fig. 2.1. Interactions between soil organic carbon (SOC) and the five essential services. Solid lines
represent links discussed in this manuscript that refer directly to SOC. Dashed lines are interactions among
essential services to show the interconnectivity.