It is more difficult and costly to build housing at a large scale in the Green Belt than many of its detractors argue. The MP Siobhain McDonagh has recently stated that it is possible to build a million new houses on 20,000 hectares of Green Belt land near to train stations on the edge of London. The claim assumes that the new housing will be built at the relatively high average density of 50 houses per hectare. In many cases this will simply not be possible on a Green Belt site, due to the need to also provide other supporting infrastructure such as roads, schools, sewerage and so on. Also, the mapping underlying the claim does not take into account environmental assets such as public footpaths, ancient trees or hedgerows.
The figure comes from the Adam Smith Institute and several other bodies who come to the same conclusions because they are working off the same GIS data of areas given para. 14 protection in the NPPF (AONB etc.)
The problem is not distinguishing between net and gross density, a housing site is not just housing, 30-40% will be open space, roads and community facilities, before you even consider undevelopable areas (in planning jargon its known as the exaction rate). So rather than 1 million home it would be closer to 660,000, unless the density were to increase to around 66 DPH, around that of tight terraced housing. At which point those in favour of Green Belt release might reply – so what.
The real issue though is whether this is sensible and achievable. Most commuter lines into London have limited track and terminus capacity, so many posts on this blog have been looking at locations where this could be increased and ideas to increase headway and terminal capacity in Central London.
The real opportunities are schemes and ideas such as Oxford Cambridge Rail, restoration of the Great Central Line, dual tracking of the Mid Cheshire Line, HS5 to Cambridge and Norwich, and several other potential schemes in Kent, Surrey and the Great Western Network which ill blog about on here shortly
A few of these sites are within the Green Belt, but the scale of the challenge and the locations where this scale could be met are mostly outside of the Green Belt. The real threat to the Green Belt is not in the South East but the North West where the largest losses are proposed and gaps between towns much smaller. The real threat to the south East Green Belt is, in the great scheme of things, rather trivial around 2% loss in most local plans and in good part on large brownfield sites.