In the absence of any serious debate about how to more fairly distribute our housing resources (ie address unsustainable levels of under-occupation) the clarion call is for the building of housing in the order of 250,000 per year. Part of that discourse is the questioning of the current Green Belt boundaries around most of our urban conurbations.
DanthePlan is not going to rehearse all the arguments for retaining or reviewing Green Belts but will raise a few of the issues which are not given sufficient attention.
It it not inevitable that the origins of the green belts set out in the Government Circular 42/55 'Green Belts' issued in August 1955 remain relevant to spatial planning in 2015, however this circular is referred to selectively by those involved in the current debate. My favourite but least heard quote is,
"...within urban areas thus defined, every effort should be made to prevent further building for industrial or commercial purposes; since this, if allowed, would lead to a demand for more labour, which in turn would create a need for the development of additional land for housing."
Since 1955 some ineffective attempts were undertaken to plan for the location of industry and offices (who remembers Industrial Development Permits and Office Development Certificates and the Location of Offices Bureau?). However, councils have mostly regarded the growth of jobs as a good thing to be secured at any cost. The cost to the places where jobs have been secured has been the foreseeable rise in the price of housing for purchase and rent. These price rises have been greater within the Green Belts and reducing with distance/time for commuting by road or public transport into the urban area and employment centres. Planning authorities that have made inadequate attempts to, "...prevent further building for industrial or commercial purposes...", should not now be seeking to protect the original Green Belt boundaries. Unfortunately the councils controlling outer Green Belt boundaries are often those wanting these to remain unchanged but having no control over the employment growth in the encircled urban area. the Duty to Cooperate is no substitute for regional planning authorities (removed by Eric Pickles during the 2010 administration).
A repeated complaint arising from the uncontrolled employment growth is the level of commuting and the consequent congestion and carbon emissions. The intelligent response is to ensure that housing is concentrated along public transport corridors and especially at railway stations. There are few cases for using planning as a surrogate transport policy and the phenomenon of commuting from existing satellite housing should be tackled now, without worrying about or waiting for new housing eg severe restrictions on parking within the urban area and park and ride facilities (re)located outside the Green Belts.
Finally, Green Belts should be used for recreation and agriculture/forestry. These land uses are generally ignored by the planning system. This should change, and development plans should include permissive policies supporting the development of residential accommodation for agricultural workers' dwellings in the Green Belt, but tied by conditions or planning obligations to agricultural/horticultural regimes that include growing local food and the enhancement of bio-diversity (including under the ground) and even the appearance of the landscape and public access/rights of way. See (ie Google) Ecological Land Cooperative.
So Green Belt boundaries should be maintained for the purposes of developing local food systems and not for (unrelated) housing, that could be located anywhere convenient for the use of public transport, whether in the urban area or beyond the outer boundary of its Green Belt.