FOR 50 years, Britain's Green Belts have restricted urban sprawl. They are an effective way of checking development. The idea behind Green Belt policy is simple: to permanently prevent building on open space. But its application is far from simple.

For example, some development on Green Belt land is positive. One stated aim of such land is to provide recreational opportunities. That is why York Racecourse is allowed to operate within the city's Green Belt.

Council leaders also argued that the development of the Rawcliffe Park and Ride site was acceptable use of the Green Belt, although environmentalists disagreed.

Operating Green Belt policy is, therefore, a tightrope walk. Regional Planning Guidance on its application for York is succinct. It "should seek to preserve the setting and special character of York, while at the same time taking account of the need to promote sustainable patterns of development". In other words, the Green Belt should hold in urban sprawl without entirely strangling York's future prospects for growth.

City of York Council is now reviewing its Green Belt. Areas protected by this status include the strays and floodplains which run into the city as well as the areas on its boundaries.

The council is asking for residents' input. This is useful in that it will raise awareness of the issue. But councillors must already know what the overwhelming public opinion will be: leave our Green Belt alone. That view should remain at the heart of any Green Belt reforms. Otherwise, this public consultation will be seen as a cosmetic exercise.

The council is under intense pressure to find new building land for both industry and housing. But that only makes the Green Belt more important than ever.

If any land is to be sacrificed by this review, it must be the bare minimum for developments that are utterly essential for York's future prosperity. And the council should reassure the city that the Green Belt will continue to protect York from over development.