Campaigners say many common ground sites are under threat
A campaign has been launched by the Open Spaces Society to highlight the threats to common land in England.
The group says that, despite having legal protection, common land is in danger of disappearing through neglect.
Such spaces are highly important for wildlife and public recreation, say researchers.
The OSS's general secretary, Kate Ashbrook, says much common land will disappear under vegetation unless managed with grazing livestock.
Common land, despite its name, is not publicly owned, but is land owned by one person, over which another has rights.
These include rights to graze animals, to cut bracken for livestock bedding or to allow pigs to eat fallen acorns.
BBC environment correspondent Sarah Mukherjee said that 400 years ago half the land in England was common land, but that figure has shrunk to just 3%.
And much of the remaining space, according to the Open Spaces Society, is under threat.
"People still have common rights which tend to come with their houses - but changing lifestyles tend to mean that people don't use them," said Ms Ashbrook.
"Because common lands have been unploughed since mediaeval times, they're great for wildlife. But they do need regular grazing to keep them in order."
Hampshire County Council, Hart District Council, Natural England, the Hampshire and Isle of Wight Wildlife Trust have now all combined with the OSS to produce a DVD called Common Vision, which focuses on lowland commons and why they are important.
Solutions and compromises
Ms Ashbrook also said that local authorities and residents need to work together to ensure common land remains open in the future.
She added: "The magic of the commons is that they are all open to public access on foot by law, and on some there are rights to ride.
"At the same time they are habitats for a fabulous variety of species. Everyone has a common near to where they live.
'The problem is how to defend them. On many it is essential to have animals grazing to prevent overgrowth by scrub, but the danger is that sheep or cattle will wander onto roads and be killed.
"Yet fences destroy the open freedom of the commons. We must look for other solutions and new compromises."