England has a land area of just under 13,046,200 hectares (according to the Office for National Statistics). Of this area only about 11 per cent is developed.
Allowing for overlaps, about 40 per cent of the area of England (5.3 million hectares) is protected against development by one or more environmentally-protected designations.
As well as designated Green Belt land, this estimate covers National Parks, Areas of Outstanding Natural Beauty (AONBs) and Sites of Special Scientific Interest (SSSIs).
Once Green Belts have been defined, local planning authorities should plan positively to enhance the beneficial use of the Green Belt, such as looking for opportunities to provide access; to provide opportunities for outdoor sport and recreation; to retain and enhance landscapes, visual amenity and biodiversity; or to improve damaged and derelict land. Local authorities are encouraged to regularly review whether their designated Green Belt continues to meet the five purposes of the Green Belt outlined above.
Should the area no longer serve the stated purposes, an authority may consider whether other designations are appropriate, for example, Local Green Space. As such, a decrease in the land designated as Green Belt does not necessarily result in a decrease in the amount of land protected from development
The extent of the designated Green Belt in England as at 31 March 2018 was estimated at 1,629,510 hectares, around 12.5% of the land area of England.
Overall there was a decrease of 5,070 hectares (0.3%) in the area of Green Belt between 31 March 2017 and 31 March 2018.
In 2017/18, ten local planning authorities adopted new plans, with the result being a net decrease in the overall area of Green Belt compared to 31 March 2017.