Our green spaces - whether fields or scrubland, woodland or bog - are the background of our ecology.
They are habitat for countless species of wild animals, insects and other creatures. The trees they contain oxygenate the air, and some even absorb pollution from our towns and cities, cars and other transport systems.
If we fail to safeguard the green belt - an area originally designated as off-limits from development - then we are adding to the potential for even higher levels of lung and heart disease from increased pollution, and our wildlife will be diminished, and in some cases, lost entirely.
This group has formed - as have other groups all over Britain - to protect this vital green safety-net from encroachment by building development.
Photograph: Ketul Patel