A Strategy for Taking Soil Carbon into the Policy Arena - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 70

climate-smart agricultural practices and a
database of agriculture, forestry and other
land-use mitigation projects (AFOLU MPs).
It includes few agricultural SOC projects,
but these are expected to increase as the
capacity to use new methods and tools in-
creases (McCarthy et al ., 2011). Other pro-
grammes include the Intergovernmental
Panel on Climate Change (IPCC) Emission
Factors database, which is a repository for
the site-specific stock change and emission
factors needed to make estimates of changes
in C stocks in both biomass and soils, and
the FAO's Harmonized World Soils data-
base, which includes local-level informa-
tion on SOC stocks. One of the main gaps
in these programmes, which hinders the
estimation of SOC stocks and changes, is
information on different land management
practices at the local level, particularly in
developing country areas dominated by
smallholders.
There are many examples of tools and
models that can be used to make estimates of
SOC stocks and changes at the local level
(Chapter 17, this volume). Some are based on
the IPCC's computational method (CBP Sim-
ple and Detailed Assessment, EX-ACT, Cool
Farm), others use dynamic ecosystem models
(COMET Farm, COMET VR). Constraints in-
clude the fact that most models have originally
been developed using data from temperate
areas and are therefore less applicable to
tropical conditions. Two recent reviews con-
sidered tools that could be used to make
landscape-scale estimates of C stock changes
in soils and biomass. Colomb et al . (2013)
consider 18 tools covering different geo-
graphic areas, and the authors are currently
developing an online application that will
allow users to choose the most appropriate
tool. The second review considers tools that
can be used in developing countries in areas
dominated by smallholder agriculture, an im-
portant area for the future consideration of
global SOC stock change (Milne et al ., 2010,
2013). There is a need for capacity building
for the use of local-level tools and methods
and to develop local-level tools based on dy-
namic models that are applicable to condi-
tions in tropical areas and other areas of rapid
land-use change.

National

Making national-scale estimates of SOC
stocks and changes is dependent on avail-
able soil survey information, which can be
incomplete and of varying quality in many
countries (Batjes et al ., 2007). Parameters
such as bulk density, which are needed to
estimate SOC stocks, are often missing. Sub-
stantial work has been carried out by the
International Soil Reference and Informa-
tion Centre (ISRIC) to complete national-
scale information on SOC in the soil and
terrain (SOTER) database using collations
of existing data sets, pedo-transfer functions
and expert opinion (Batjes et al ., 2007). In
terms of the ongoing collation of SOC infor-
mation at the national scale, many countries
have programmes for national-scale survey
and monitoring. van Wesemael et al . (2011)
summarized existing Soil Monitoring Net-
works (SMNs). Networks were found to
have different criteria in terms of land types
sampled, sampling depth and frequency of
sampling. Harmonization of SMNs would
allow the comparison of different national-
scale SOC stocks, and would also facilitate
the use of national-scale models. A problem
among almost all networks is continuity of
the funding needed for ongoing monitoring.
In terms of the tools available for the
estimation of SOC stocks at the national
scale, empirical methods that use know-
ledge of soil type, climate and land use have
been used frequently to estimate stocks (Lal
et al ., 2006; Batjes et al ., 2007). There are
also tools for estimating stock change at the
national scale, including those based on
computational methods where a stock at one
point in time is subtracted from another.
Tools also exist that employ dynamic models
which attempt to capture the dynamic na-
ture of the decomposition of organic matter
over time. The World Bank Agriculture and
Rural Development programme has an on-
line tool that employs the RothC model to
make national-scale estimates of SOC change
over a 25- year period. Users can input infor-
mation on different land management prac-
tices to alter estimates (ARD, 2013). A more
rigorous but less user-friendly tool is the
Global Environment Facilities GEFSOC tool