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Data Sources and Methodology
Data on woodland area in the UK presented in this release are derived from the following sources:
Estimates of woodland area in Great Britain are based on figures produced from forest inventories. Until recently, forest inventories in Great Britain were undertaken every 15 years or so. The current National Forest Inventory (NFI), unlike previous inventories, is planned to run on a continuous 5-year cycle.
As forest inventories are generally not designed to produce annual figures, a process is required for updating the results on an annual basis to take account of changes in woodland area. The methodology currently used to calculate annual woodland area estimates is described below.
The data processing takes place in Excel. The main outputs are aggregates from the source data, or breakdowns expressed as percentages, and do not require complex data analysis techniques.
1. For Great Britain, woodland area estimates are based on the latest NFI woodland area map of Great Britain available. In this release, final woodland area estimates at March 2015 and provisional estimates at March 2016 are both based on the NFI woodland area map at March 2015.
2. The map is overlaid with a map of Forestry Commission and Natural Resources Wales (ex Forestry Commission Wales only) land, to enable a breakdown by ownership to be estimated. This also enables FC/NRW “other land” areas to be derived (Table 1.5). For final woodland area estimates at March 2015, FC/NRW legal boundaries at March 2015 are used, and for provisional estimates at March 2016, FC/NRW legal boundaries at March 2016 are used.
3. The woodland area breakdown by type of woodland (conifer or broadleaf) is estimated from the conifer/broadleaf breakdown of stocked woodland area, with areas of felled and open space allocated to conifer or broadleaf pro-rata. Estimates for stocked areas at March 2012 derived from NFI interim field survey results are updated to take into account new planting since that date, for which the conifer/broadleaf breakdown is also known. As the area of new planting is much smaller than total woodland area, the effect of this update on the overall conifer/broadleaf breakdown is very small.
The steps above are sufficient to determine final woodland area estimates at March 2015, broken down by ownership and conifer/broadleaf.
To obtain provisional estimates at March 2016, two more steps need to be performed, which are described below.
4. Net ownership transfers of woodland between private sector and FC/NRW from March 2015 to March 2016, as inferred by the differences in FC/NRW legal boundaries between those two dates, are broken down by conifer/broadleaf. The breakdown is based on NFI Interpreted Forest Type (IFT) at those dates, derived from photographic interpretation of the NFI woodland map. The “Conifer” and “Mixed mainly conifer” (>80% conifer) IFT categories are assigned to conifers, and the “Broadleaves” and “Mixed mainly broadleaved” (>80% broadleaved) categories are assigned to broadleaves. For the other IFT categories, the conifer/broadleaf breakdown is allocated pro-rata based on the conifer/broadleaf breakdown of woodland area by ownership (private sector or FC/NRW) before transfer.
5. The woodland area figures are then updated to March 2016 by adding areas of new planting in 2015-16, broken down by ownership and type.
Information on previous methodologies can be found in the Methodology Note: Annual Woodland Estimates produced in May 2012, on the Methodology and Outputs web page at www.forestry.gov.uk/forestry/ahen-589ddl.
The methodology and outputs relevant to UK woodland area, planting and restocking were reviewed in 2014. The review report is available at mrwapr.pdf.
Further information on the methodology used by the National Forest Inventory and comparisons of results from the NFI and previous woodland area estimates is available at www.forestry.gov.uk/inventory.
Figures for Northern Ireland (Forest Service and non-Forest Service woodland) are provided by the Forest Service (http://www.daera-ni.gov.uk/topics/forestry). Woodland areas from 2012 provided in this release have been obtained from the NI woodland register.
The NI woodland register is based on a combined dataset derived from fourteen individual datasets from statutory bodies including Forest Service, Land and Property Services, and the Northern Ireland Environment Agency, and non statutory bodies which include Woodland Trust and National Trust. The minimum area of woodland that has been included in the register is 0.1 hectares.
The use of the NI woodland register has resulted in a step change in the non-Forest Service woodland areas reported for Northern Ireland. This should be interpreted as an improvement in the data reported, rather than an actual increase in woodland area.
Further information on administrative sources can be found at: www.forestry.gov.uk/forestry/infd-832ey5.
Certified woodland area
Data on certified woodland areas are obtained from the Forest Stewardship Council (FSC), and contact with individual land owners and managers. Some of the certified woodland has dual certification, i.e. it is certified under both the FSC scheme and the Programme for the Endorsement of Forest Certification (PEFC) scheme.
The data collected from FSC are the areas that are certified for each certificate holder. Follow-up enquiries are then made with larger certificate holders to check the certified areas and to provide a country breakdown.
As all FC/NRW/FS woodlands are certified, the total woodland area (as derived above, from the NFI map and FC boundaries and from Forest Service administrative records) is used, rather than the area provided on the certificates.
The statistics on woodland area presented here refer to woodland as a land use rather than as a land cover, so felled areas and small areas (less than 0.5 ha) of open space are included within the definition of woodland. Some statistics on woodland area as a land cover are available from other sources (e.g. Countryside Survey 2007, www.countrysidesurvey.org.uk, and associated Land Cover Map).
Detailed information on the quality of the woodland area statistics presented in this publication is available in the “Quality Report: Woodland Area, Planting and Restocking” at:
Further quality information on FC Official Statistics is available at: www.forestry.gov.uk/forestry/infd-7zhk85.
Figures at March 2016 are final; provisional figures were previously released in “Woodland Area, Planting and Restocking: 2016 Edition”. Figures at March 2016 and for earlier years have not been revised from those published in “Woodland Area, Planting and Restocking: 2016 Edition”.
Information on revisions made since “Forestry Statistics 2015” are provided in “Woodland Area, Planting and Restocking: 2016 Edition”.
Information on significant revisions to published statistics is provided in the quality report on Woodland Area, Planting and Restocking, available from our Quality web page at www.forestry.gov.uk/forestry/infd-7zhk85.
The Forestry Commission’s revisions policy sets out how revisions and errors are dealt with and can be found at FCrevisions.pdf.
Accompanying tables to this release, available at www.forestry.gov.uk/forestry/infd-7aqknx, provide longer time series data by country for certified woodland.
Figures for woodland area in the UK are provided to international organisations; the Food and Agriculture Organisation of the United Nations (FAO) for the 5-yearly “Global Forest Resources Assessment” (www.fao.org/forest-resources-assessment/en/), and Forest Europe for the 4-yearly “State of Europe’s Forests” (www.foresteurope.org/reporting_SFM).
Figures for woodland area are also used to compile the UK’s Greenhouse Gas Inventory for the Land Use, Land Use Change and Forestry (LULUCF) sector, submitted to the United Nations Framework Convention on Climate Change (UNFCCC, http://unfccc.int/national_reports/annex_i_ghg_inventories/national_inventories_submissions/items/8812.php). Summary factsheets, produced by the Department for Business, Energy and Industrial Strategy (previously the Department of Energy and Climate Change), are available at www.gov.uk/government/publications/uk-greenhouse-gas-inventory-summary-factsheets.
Woodland area and certified woodland area data are released twice a year. Provisional figures are published in Woodland Area, Planting and Restocking in early June. Final figures are released in Forestry Statistics at the end of September.
Provisional figures for woodland area and certified woodland area at March 2017 will be published on 15 June 2017 in “Woodland Area, Planting and Restocking: 2017 Edition”.
Final results for woodland area and certified woodland area at March 2017 will be published on 28 September 2017 in “Forestry Statistics 2017” and “Forestry Facts & Figures 2017”.
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