Report by SRUC, JHI & Forest Research 2018.

Executive Summary:

Soil carbon has been identified as a priority issue by the Scottish Government in climate change
policy across several areas. There is particular interest in the potential of soils to provide
carbon sequestration as a contribution to the annual emissions reductions targets, with links
to agriculture, renewable energy and other primary land uses.
This project synthesises the current state of knowledge on soil carbon and land use in Scotland.
1. Key findings
 There is strong scientific evidence of consensus in several key areas including the importance
of Scottish soils for the storage of carbon, and the amounts of carbon stored in different soil
types across the country
 There was an absence of evidence around potentially key issues including the amount of
carbon that can be sequestered by restoration of organic soils, rotational grass, the future
carbon sequestration potentials of long term grasslands and arable soils
 The evidence base is consistent on the overall levels of soil carbon in Scotland (around 3000
Mt), and on the amount (1600 Mt) stored in peats and peaty soils.
 The available evidence suggests that there have been no significant changes in the storage of
carbon taking place in arable or grassland soils since 1978. However, it can be demonstrated
that older grasslands (greater than 5 years) will store more carbon
 The uptake of atmospheric carbon dioxide (CO2) by land use and land use change (10 Mt
CO2e/year) is of a similar magnitude to the total greenhouse gas emissions from agriculture in
Scotland
 There is broad agreement across the evidence studied that some opportunities exist to use
agricultural management to increase carbon storage in agricultural soils (estimated to be 174
Mt C), although there are possibly greater opportunities to reduce non CO2 greenhouse gas
emissions from agriculture (currently 7.4 Mt CO2e/year)
 Emissions of gases other than CO2 (methane and nitrous oxide) dominate agriculture’s
contribution to greenhouse gas emissions. An improved understanding to these emissions is
likely to lead to greater opportunities for mitigation than that provided by increasing carbon
sequestration
 The evidence base is consistent in the conclusion that peatland restoration offers significant
opportunities to increase carbon storage in Scottish soils but there are large uncertainties
(ranging between a net uptake of 8.1 Mt CO2e/year to net loss of 2.8 Mt CO2e/year )
 There are considerable uncertainties in predicting the future effects of land use change,
climate, and management and their interactions on future carbon stocks. This is due to
uncertainties in future global atmospheric greenhouse gas concentrations, and the
consequent response of soils to altered climatic conditions
 The UK and Scottish inventories of greenhouse gas emissions and removals do not currently
report changes in soil carbon stocks in areas of grassland and cropland that remain in the same land use. As new evidence emerges of such changes it is likely in future that new reporting
procedures will be adopted that reflect such changes
 Work is ongoing in trying to establish better emission factors for the UK peatlands. It is
expected that the findings of a DECC-funded project, which will collate both the historic and
the most recent UK-relevant data, will be published in the near future.