Green belt land is a policy and land-use zone designation used in land-use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding or neighboring urban areas. Green belts are a buffer between towns and between town and countryside, and the aim of green belt policy is to prevent urban sprawl by keeping land permanently open. Green belt lands may include open spaces, parks, farms and ranches, wildlands, or a combination thereof, as designated by cities, counties, special districts, and other jurisdictions. The primary purpose of the Green Belt Policy is to mitigate unsustainable urban sprawl by aiming to keep available land spaces open permanently. The benefits of green belt lands include preserving local biodiversity and natural resources, offering space in the event of flooding to safeguard an already scarce water supply, and capturing excess carbon dioxide with their large amount of trees or forests. Green belt lands are also essential to the economy, as they provide fresh water, wildlife habitat, and protection against the effects of climate change. In some countries, green belt policy is implemented through legislation, such as the Agricultural, Forest and Open Space Land Act of 1976 in Tennessee.