Wooded areas included in the ancient woodland inventories. The first ancient woodland inventories were compiled in the 1980s for England, Wales and Scotland. They were based on the date of the earliest reliable maps.
An ancient woodland must have been wooded continuously since the relevant national baseline date: 1600 for the England and Wales inventories, and 1750 for Scotland. The more recent inventory for Northern Ireland is based on the first edition of the Ordnance Survey maps, which were produced in 1830. These inventories are revised as new information becomes available.
National categories of ancient woodland differ, but the main categories in England, Wales and Northern Ireland are:
Ancient Semi-Natural Woodland (ASNW): areas of mainly native tree and shrub species that have regenerated naturally rather than being planted.
Plantations on Ancient Woodland Sites (PAWS): areas of ASNW that were subsequently converted to plantations of non-native tree and shrub species.
Ancient woodlands are subject to a varying degree of national planning protection to safeguard their diverse ecology.