As they have the same landscape quality, AONBs may be compared to the national parks of England and Wales. AONBs are created under the same legislation as the national parks, the National Parks and Access to the Countryside Act 1949. Unlike AONBs, national parks have their own authorities, have special legal powers to prevent unsympathetic development, and are well known to many inhabitants of England, Wales and Northern Ireland. By contrast, there are very limited statutory duties imposed on local authorities within an AONB and there is evidence to indicate many residents in such areas may be unaware of the status. However, further regulation and protection of AONBs was added by the Countryside and Rights of Way Act 2000, and the Government has recently stated that AONBs and national parks have equal status when it comes to planning consent and other sensitive issues.
There are 35 AONBs in England, four in Wales, one (Wye Valley) that is in both England and Wales and nine in Northern Ireland. The most recently confirmed is the Tamar Valley AONB in 1994. AONBs vary greatly in terms of size, type and use of land, whether they are partly or wholly open to the public. All English and Welsh AONBs have a dedicated AONB officer and other staff. The smallest AONB is the Isles of Scilly (1976), 16 km², and the largest AONB is the Cotswolds (1966), 2,038 km². The AONBs of England and Wales together cover around 18% of the countryside in the two countries. The National Association for AONBs is an independent organisation acting on behalf of AONBs and their partners.
There are growing concerns among environmental and countryside groups that AONB status is increasingly under threat from development. The Campaign to Protect Rural England said in July 2006 that many AONBs were under greater threat than ever before. Three particular sites were cited: the Dorset AONB threatened by a road plan, the threat of a football stadium in the Sussex Downs AONB, and, larger than any other, a £1 billion plan by Imperial College to build thousands of houses and offices on hundreds of acres of AONB land on the Kent Downs at Wye. Imperial College have now withdrawn their plans for development, seemingly to the disappointment of both Ashford Borough and Kent County councils (September 2006). In September 2007 Government approval was finally given for the development of a new football ground for Brighton and Hove Albion within the boundaries of the Sussex Downs AONB, after a fierce fight by conservationists. It has since been announced there will be no further appeals against this decision, and building work is expected to commence in late 2008/early 2009.