Nature Conservancy Council and English Nature: Ancient Woodland Inventory Dataset
Nature Conservancy Council and English Nature: Ancient Woodland Inventory Dataset
The Ancient Woodland Inventory (AWI) is an electronic dataset which identifies and records information about ancient woodland in England. For the purposes of the Inventory, 'ancient' woods are those which are believed to have been in existence since at least 1600 AD and which have only been cleared for underwood or timber production. The Inventory covers woodland sites which had an area of at least two hectares on the Ordnance Survey's First Series 1:25,000 maps. Smaller woods are excluded. It includes ancient semi-natural woodland, ancient replanted woodland and ancient woodland sites which have been cleared since the surveying for the Ordnance Survey First Series 1:25,000 maps.
The AWI covers the following types of woodland:
- Ancient semi-natural woodland: 'all stands of ancient woodland which did not obviously originate from planting'. The following are included in this category in the AWI: birch woodland on disturbed ground inside ancient woods; small semi-natural stands within ancient sites which have developed on former settlements, gravel pits etc.; woods where semi-natural stands have been slightly modified by planting; and woods containing some self-sown sycamore.
- Ancient replanted woodland: 'obviously planted woodland of any age of a broadleaf, mixed or coniferous type, identifiable from field survey'. Plantations of any coniferous species, sycamore, poplar, red oak, southern beech 'and native species planted so densely that the semi-natural underwood is suppressed' are automatically included in this category. 'Ancient replanted woodland' excludes beech north of the Chilterns and Cotswolds, and includes sweet chestnut in Kent and other south eastern counties 'unless it can be shown that they are suppressing the other semi-natural components of the underwood'.
- Ancient woodland sites which have been grubbed: woods which have been cleared for agriculture, mineral extraction or urban development since the publication of the Ordnance Survey First Series 1:25,000 maps.
A single woodland site in the AWI may comprise one or more of the above types.
Three main products have resulted from the Inventory and have been used to disseminate AWI data:
- (1) Published reports - known as provisional county inventories - which summarise the results of the AWI for each of the post-1974 counties of England. The reports give an overview of the methodology and findings of the AWI, and include 1:50,000 maps showing the location of ancient woodland. The reports were accompanied by summary tables and printouts of wood-level data for each county. The reports are known as 'provisional' because of the expectation that the information will be revised as new or more detailed data about woodland is received. Some have gone through several editions. English Nature also issued a series of separate Research Reports, summarising changes to the AWI, which could be used to update the provisional county inventories.
- (2) A database holding data gathered in the AWI for all of England, with records for individual woodland sites. This dataset is derived from this database.
- (3) A dataset of digital boundary data capable of being loaded into a geographical information system (GIS). Between 1995 and 1999 a joint project between English Nature and the Forestry Commission digitised the boundaries of ancient semi-natural and ancient replanted woodland sites. This resulted in a GIS dataset consisting of digital boundaries (digitised at 1:25,000 scale) for each site, plus information calculated by the GIS such as grid reference, total area, semi-natural area and replanted area. At the time of transfer of the first AWI dataset to NDAD (2001-2002), AWI digital boundary data could be downloaded from English Nature's web site.
Three tables (AWISITE, AWITNR and AWISTRV) record information about woodland sites, while four other tables act as lookup tables for fields in AWISITE, AWITNR and AWISTRV. AWISITE contains the main data on woodland sites and provides the following information on individual sites:
- An identifier for the site which acts as a link to the AWITNR and AWISTRV tables and to the GIS data.
- The name (or names) of the site, including an indicator as to whether the name was a local name or one created for the purposes of the Inventory.
- Data on the site's location, including the current grid reference of the centroid of the site; the 10 km square and quadrant of the Ordnance Survey 100 km square in which the site is located; the grid reference of the centroid of the site at the time of the First Series 1:25,000 maps (which may be different from the current grid reference); and the parish (or parishes), county and 'Natural Area' in which the site is located. ('Natural Areas' are high-level subdivisions of England created by English Nature as a way of interpreting the ecological variations of the country in terms of natural features).
- The extent of the site (in hectares), including the original area of the site at the time of the OS First Series 1:25,000 maps; the current area of the site; the area cleared of woodland since the OS First Series maps; the area of ancient replanted woodland; and the area of ancient semi-natural woodland.
- An identifier linked to the SITE lookup table, which identifies any Site of Special Scientific Interest (SSSI) associated with a woodland. Other fields record the total area of woodland designated as SSSI and the area of ancient semi-natural woodland designated as SSSI.
- The total 'designated area' of the site in hectares, and the 'designated area' comprising ancient semi-natural woodland.
- Assessments of the reliability of historical information about the site, and the reliability of recent knowledge of the site.
- An identifier (linked to the TEAM table) for the English Nature team whose area covered the ancient woodland site.
Digital boundary data relating to the AWI has not yet been transferred.
The datasets in this series are available to download. Links to individual datasets can be found at piece level.
Hardware: Before 1991, AWI data was held by the Nature Conservancy Council on a PR1ME '2255 minicomputer'. At time of transfer in 2001-2002, the database was probably available via networked PCs linked to a server.
Application software: Before 1991 the data was held in a PR1ME Information, PR1ME's database management system. By 1995 the AWI database was part of English Nature's CORDATA information system. The data was held in an Informix UniVerse database with a 'front end' provided by Informix SystemBuilder+. When the AWI was moved from CORDATA to a new information system (ENSIS) in 1995-1996, UniVerse was replaced by Oracle and SystemBuilder+ by Compuware's UNIFACE.
Logical structure and schema: At time of transfer in 2001-2002, the AWI database was held by English Nature in an information system known as ENSIS (English Nature Sites Information System). ENSIS was itself part of a wider system, TENIS (The English Nature Information System). The AWI database was integrated into ENSIS in 1995-1996 as part of the replacement of an earlier information system, CORDATA, of which the AWI database had been a component. CORDATA in turn had replaced a previous system, COREDATA.
The dataset consists of seven tables, four of which are lookup tables linked in 1:many relationships to the main AWISITE table. AWISITE is linked in a 1:many relationship to AWISTRV (ancient woodland revisions), and in a 1:many relationship to AWITNR. Of the lookup tables, SITE was only supplied in part, while NDAD did not receive the CUSTMR table which in ENSIS acted as a lookup table for the CUSTMR_ID field in AWITNR.
How data was originally captured and validated: The AWI was preceded by trials in Norfolk, Lincolnshire and Nottinghamshire. These indicated that it was feasible to identify ancient woodland sites using information from maps and existing survey data, rather than by carrying out field surveys.
The initial stage of the data gathering process involved identifying woods over two hectares on Ordnance Survey First Series 1:25,000 maps, surveyed between 1880 and 1960. These provided a 'base line' for the Inventory, and were used because they excluded afforestation which had occurred since 1945. Other sources used in conjunction with the First Series maps include:
- Earlier 19th century Ordnance Survey maps, including First Edition 1:63,360 maps (surveyed 1805-1873) and 1:10,560 'County Series' maps (largely surveyed by 1900); pre-Ordnance Survey county maps from the 18th and early 19th centuries; and 17th and 18th century estate maps. Likely areas of ancient woodland were identified by their presence on the maps, and as a result of map features which were felt to indicate ancient woodland. These included a wood's name, its situation in the landscape, the nature of the surrounding pattern of enclosure, and the pattern of boundaries in the wood.
- The following were also used as indicators that a site might be ancient: records of ancient boundary features, the presence of a coppice-with-standards or a coppice structure, evidence of former pasture-woodland management, and the presence of species associated with ancient woodland.
- Previous field surveys, published sources, forestry stock maps and information from woodland landowners were used to determine the extent of woodland sites, and whether they were ancient semi-natural woodland or ancient replanted woodland.
- Aerial photographs were examined to determine the current extent of woods, distinguish between ancient semi-natural woodland and ancient replanted woodland, and measure the extent of woodland loss since the First Series maps.
The areas of ancient semi-natural, ancient replanted and ancient cleared woodland were measured on projections of the First Series maps using a romer dot grid overlay. For each woodland considered by the AWI, a data sheet was prepared summarising the information which had been used to determine whether the wood should be included in the Inventory. Data was input to the AWI database for those sites which had been identified as ancient.
Since the publication of the original provisional county inventories, the AWI database has been updated on the basis of more recent surveys conducted by English Nature, local authorities and wildlife trusts, and as a result of comments from the Forestry Commission and woodland owners. Revisions were also made as a result of the project to digitise ancient woodland boundaries, which led to more accurate measurements of the extent of woodland sites. Amendments to the data have included: updating data on a site's conservation status; changes to the site's ownership information; reclassification of a site from ancient semi-natural to ancient replanted woodland (and vice versa); changes to the extent of a site; the deletion of sites or parts of sites previously considered to be ancient; and the addition of sites to the AWI based on new information.
Digital boundary data: By 1994 English Nature had digitised the boundaries of ancient woodland sites in Nottinghamshire and Cumbria, while the Forestry Commission had digitised sites in North Yorkshire. In 1995 a joint project was initiated between English Nature and the Forestry Authority (then part of the Forestry Commission) to digitise the remaining boundaries of ancient woodland in England as part of the Forestry Commission's National Inventory of Woodland and Trees. The digitisation was carried out by the Forestry Authority at 1:25,000 scale using the 1:50,000 maps in the provisional county inventory reports. For some counties 1:25,000 maps were used where available.
The digitisation project is thought to have been completed in 1999. When the first AWI dataset was transferred in 2001-2002, AWI digital boundaries and associated data from the AWI database could be downloaded from English Nature's web site as 26 separate files based on Ordnance Survey grid letters. Each file could be split into up to four sub-files based on 50 km x 50 km Ordnance Survey 'tiles' or quadrants.
Constraints on the reliability of the data: The general limitations of the AWI are discussed in the report by Spencer and Kirby, 'An Inventory of Ancient Woodland for England and Wales' (found in the dataset documentation catalogue). The limitations of the digital boundary data are discussed in English Nature Research Report 313. In particular, it should be noted that the AWI's approach has been to include rather than exclude borderline sites. Sites have been retained in the Inventory even if there is uncertainty over whether they should be classed as ancient, on the grounds that this will allow their status to be re-appraised when more information becomes available.
Nature Conservancy Council, 1973-1991
The Ancient Woodland Inventory (AWI) grew out of recognition in forestry circles, by the late 1970s, of the importance of ancient woodland in nature conservation. Studies by George Peterken and Oliver Rackham emphasised the distinctive nature of woods which had existed since medieval times, as opposed to woods which had been planted or grown up naturally in the last few centuries. Ancient woodland sites often contain communities of animals and plants which are confined to, and dependent for their existence upon, ancient semi-natural woodland. Many natural characteristics of such sites, such as woodland composition and soil profile, are important to nature conservation and may be relics of the original natural forest cover. Ancient woodland can also contain historical landscape and archaeological features which are important in their own right. It was recognised that ancient woodland was subject to particular pressures and was declining, particularly in eastern England, due to the conversion of semi-natural woodland to plantations and farmland.
The original aims of the AWI were to:
- Provide an estimate of the extent and location of ancient woodland.
- Indicate the extent of losses of ancient semi-natural woodland, and act as a baseline against which further changes to ancient woodland could be measured.
- Help in planning more detailed surveys.
- Assist in the selection of Sites of Special Scientific Interest (SSSIs).
- Provide information of use to other conservation organisations.
- Be useful in discussions about forestry policies for broadleaved woodland.
When it was launched in 1981 by the Nature Conservancy Council, the AWI was intended to be an inventory of woods in Great Britain as a whole. Parallel inventories were carried out in Wales and Scotland as well as in England. In 1991 the Nature Conservancy Council was replaced by English Nature. English Nature dealt with nature conservation in England only, and inherited responsibility for the English part of the AWI. Scottish Natural Heritage and the Countryside Council for Wales were established to cover Scotland and Wales, respectively, and appear to have taken over the inventories in their countries.
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