The current National Forest Inventory is the first continuous inventory of British woodlands and is being conducted on a five year cycle. Prior to the National Forest Inventory, a series of one-off woodland inventories took place in Great Britain every 15 years or so.
Most inventories used slightly different definitions of woodland, so some apparent changes in area over time are due to changing definitions. The principal differences for inventories since 1905 are:
- 1905 Felled areas and scrub were not included.
- 1924 Undertaken by questionnaire; woods smaller than 2 acres (0.8 hectares) were not included.
- 1947 Woodlands with an area of less than 5 acres (2 hectares) were not included.
- 1965 Woodlands with an area of less than 1 acre (0.4 hectares) were not included.
- 1980 Woodlands with an area of less than 0.25 hectares were not included.
- 1995-99 Woodlands with an area of 0.1-2 hectares were included on a sample basis; some woodland missing from earlier surveys was included.
- 2010 on All woodlands with an area of 0.5 hectares or more have been included; all woodlands below 0.5 hectares have been excluded.
Estimates of woodland area prior to 1905 have been obtained from a variety of sources, including:
- Domesday Survey of England - for information in 1086;
- Scottish Woodland History (TC Smout ed, 1997) - for estimate for end Middle Ages in Scotland;
- Roy maps c1750 - for Scotland 17th Century estimate.
National Forest Inventory
In the latest inventory, a digital map based on aerial photography, satellite imagery and other data sources has been produced, from which estimates of total woodland areas have been derived. Data are currently being collected for one hectare sample squares, covering a wide variety of topics, including ownership type, species and age.
Initial results for 2010 were published for countries (Great Britain, England, Wales, Scotland) in Spring 2011. Interim results, based on field survey data combined with information from the NFI map, have since been published on the National Forest Inventory web pages at www.forestresearch.gov.uk/tools-and-resources/national-forest-inventory/.
Further information on administrative sources can be found at: www.forestresearch.gov.uk/tools-and-resources/statistics/about-our-statistics/code-of-practice/administrative-sources/
Chapter 1: Woodland Areas and Planting