Sources: UK Forests and Climate Change
Forests can help mitigate climate change by reducing the amount of greenhouse gases in the atmosphere. They do this by absorbing carbon dioxide, using the carbon to produce sugars for tree growth and releasing the oxygen back into the air. As trees grow, they store carbon in their leaves, twigs and trunk, and in the soil around them.
Globally, deforestation caused by the unsustainable harvesting of timber and the conversion of forests to other land uses accounts for almost 20 per cent of global carbon dioxide emissions. The amount of carbon stored can be increased by actions to reduce the amount of deforestation and to convert non-forested areas to forest. Forests can be managed as a sustainable source of wood – an alternative energy source to fossil fuels, and a low-energy construction material.
Woodlands can also help society adapt to a changing climate, by reducing the risk of flooding, providing shade for wildlife, reducing soil erosion and helping to cool down towns and cities.
Data sources and methodology
The diagram showing the carbon cycle is adapted from Figure 3 of Broadmeadow and Matthews (2003).
Forest carbon stock
Table 4.1 is updated from Table T8 in the final draft UK report for Global Forest Resources Assessment (FRA) 2010.
Units: This table is now shown in million tonnes carbon dioxide equivalent (MtCO2e) rather than million tonnes carbon (MtC). To convert from CO2e to C multiply by 12/44.
Timescales: Carbon stock is estimated for 1990, 2000, 2005 and 2010, as in FRA 2010.
Growing stock is taken from calculations for Table T7 of the FRA 2010. These estimations of growing stock are based on data from the 1995-99 National Inventory of Woodland and Trees and data for the FC estate.
Total biomass: These figures are updated from Table T7 of the FRA 2010, using a new "biomass expansion factor" for conifers to account for branches, foliage and other above ground biomass (Levy et al, 2004). Average densities of 0.4 ODT/m3 (oven-dry tonnes per cubic metre) for conifers and 0.5 ODT/m3 for broadleaves are taken from Jenkins et al (2011). In addition, a new "root to shoot ratio" (below ground biomass = 0.36 x above ground biomass) accounts for the below ground biomass (Levy et al, 2004).
Deadwood: Consistent with Table T8 of the FRA 2010 and Morison et al (2012), estimates of deadwood volume per hectare are taken from Gilbert (2007). These are rated up by woodland area estimates from FRA 2010 (for 1990 and 2000) and Forestry Statistics (2005 and 2010) and assuming a density of 0.45 ODT/m3.
Litter: New estimates of the carbon content of the litter layer are available from Morison et al (2012). These are rated up by woodland area estimates from FRA 2010 (for 1990 and 2000) and Forestry Statistics (2005 and 2010).
Soil carbon: New estimates of the carbon content of soil 0-100 cm for England, Wales and Scotland are available from Morison et al (2012). An estimate of the carbon content of soil for Northern Ireland is taken from Bradley et al (2005) and rated downward to reflect the generally lower carbon content found in Morison et al (2012). These are rated up by woodland area estimates from FRA 2010 (for 1990 and 2000) and Forestry Statistics (2005 and 2010). This soil estimate does not take account of soil carbon accumulation. This was previously included from estimates made by the Centre for Ecology and Hydrology in "Land Use, Land Use Change and Forestry" (LULUCF) modelling. It also assumes that the soil carbon content of afforested (and previously unwooded) land has the same soil carbon content as woodland soils, whereas in practice this may vary.
Comparison with other data sources: Figures in this updated table are now similar to the estimates made in Morison et al (2012) and McKay et al (2003).
Future updates: This table will be updated once further information is available from the National Forest Inventory.
The information in Table 4.2 is taken from inventory and projections of UK emissions by sources and removal by sinks due to land use, land use change and forestry, produced by CEH for input to 2009 final UK Greenhouse Gas Emissions (DECC, March 2011) and the National Atmospheric Emissions Inventory (NAEI, www.naei.org.uk) which incorporates all air pollutants including greenhouse gases. They exclude the pool of carbon in timber products.
Figure 4.2 shows annual estimates of carbon accumulation by country, taken from the same source but shows carbon in living forest biomass only; it excludes carbon in litter, soils and forest products. Future predictions of carbon uptake assume that commercial conifer plantations will be replanted when felled, and that planting of new woodland will continue at the same rate as in 2009 (mid projection).
Emissions and sequestration can be presented as tonnes carbon or tonnes carbon dioxide (CO2). To convert from tonnes CO2 to tonnes carbon multiply by 12/44.
Woodland Carbon Code
The Woodland Carbon Code is a voluntary standard, initiated in July 2011, for woodland creation projects that make claims about the carbon they sequester (take out of the atmosphere). All projects must be placed on the Register of UK Woodland Carbon Projects. Their claims about potential carbon sequestration are validated by an independent certification body. Validated projects are then verified on a regular basis to confirm the progress of carbon sequestration.
Information about Woodland Carbon Code projects comes from the Register of UK Woodland Carbon Projects, administered by the Forestry Commission. The register is a live database and summary data are extracted on a quarterly basis.
Further information on the Woodland Carbon Code is available at: www.forestry.gov.uk/carboncode
Further information on administrative sources can be found at: www.forestry.gov.uk/forestry/infd-832ey5
Bradley, R.I., Milne, R., Bell, J., Lilly, A., Jordan, C., Higgins, A. (2005) "A soil carbon and landuse database for the UK", Soil Use and Management 21 (363-369), DOI: 10.1079/SUM2005351 (http://onlinelibrary.wiley.com/doi/10.1079/SUM2005351/abstract)
Broadmeadow, M., Matthews, R. (2003) "Forests, Carbon and Climate Change: the UK Contribution", Forestry Commission, Edinburgh (www.forestry.gov.uk/pdf/fcin048.pdf/$FILE/fcin048.pdf)
Department of Energy and Climate Change (2011) "2009 Final UK Greenhouse Gas Emissions" (www.decc.gov.uk/en/content/cms/statistics/climate_stats/gg_emissions/gg_emissions.aspx)
Forestry Commission (2005) "Forestry Statistics 2005", Forestry Commission, Edinburgh (www.forestry.gov.uk/website/foreststats.nsf/byunique/index_main.html)
Forestry Commission (2010) "Forestry Statistics 2010", Forestry Commission, Edinburgh (www.forestry.gov.uk/website/forstats2010.nsf/LUContentsTop?openview&RestrictToCategory=1)
Jenkins, T.A.R., Mackie, E.D., Matthews, R.W., Miller, G., Randle, T.J., White, M.E., FC (2011) "Woodland Carbon Code: Carbon Assessment Protocol", Forest Research (www.forestry.gov.uk/forestry/infd-8juhc7)
Levy, P.E., Hale, S.E., Nicoll, B.C. (2004) "Biomass expansion factors and root: shoot ratios for coniferous tree species in Great Britain", Forestry, Vol 77, No 5, DOI: 10.1093/forestry/77.5.421 (forestry.oxfordjournals.org/content/77/5/421.abstract)
McKay, H. et al (2003) "Woodfuel resource in Britain", Final report B/W3/00787/Rep (www.biomassenergycentre.org.uk/pls/portal/docs/PAGE/RESOURCES/REF_LIB_RES/PUBLICATIONS/RESOURCE%20AVAILABILITY/WOODFUEL%20RESOURCE%20IN%20BRITAIN%20FILE15006.PDF)
Morison, J. et al (2012) "Understanding the Carbon and GHG balance of UK Forests", Forest Research (www.forestry.gov.uk/pdf/FCRP018.pdf/$FILE/FCRP018.pdf)
Food and Agriculture Organisation of the United Nations (2010) "Global Forest Resources Assessment 2010 – UK Report", FRA2010/221, Forestry Department, UNFAO, Rome (www.forestry.gov.uk/forestry/infd-7aqfxg)
All of the statistics in this chapter are outside the scope of National Statistics, but are included here to give a broad indication of the role of UK forests in climate change.
Statistics on UK forests and climate change obtained from others are subject to revision whenever the source data are revised.
The Forestry Commission’s revisions policy sets out how revisions and errors to these statistics are dealt with, and can be found at: www.forestry.gov.uk/pdf/FCrevisions.pdf/$FILE/FCrevisions.pdf.
For information on the release schedules of statistics produced by others, see relevant websites (above).
"Forestry Statistics 2013" and "Forestry Facts & Figures 2013" will be released on 26 September 2013.