The conservation of ancient woodland is monitored in a number of ways including the National Inventory of Woodlands and Trees, which provides data on area, ownership, species composition, age, regeneration and ecological structure of all woodland. The Ancient Woodland Inventory is updated by Natural England when changes are reported and it is being revised in some of the most well wooded parts of South East England. 15 per cent. of England’s ancient woodland is in Sites of Special Scientific Interest (SSSI) where their condition is monitored.