On a local radio interview this week I was asked if the call to build more homes in Cambridge was bad for the environment because it would mean, among other things, building on the green belt. On the contrary, building more homes in Cambridge would be a good outcome for the environment. Here’s why. 

First up, it’s important to say this: we need to build more homes. Very few people will disagree with this. But some will. So, for clarity, the below proceeds on the following – the baseline of environmental impact of new housing is not ‘no more homes built.’ 

And it’s also important to say this: contrary to seemingly widely-held beliefs, the green belt is not a special environmental designation. It was introduced purely to contain the growth of cities. A much more accurate name would be the ‘containment belt’ (Or if I was being flippant, the ‘prosperity squeezer’.) This is why the Government is looking to address this confusion and reclassify some green belt as grey belt. 

Cambridge is a good case in point of what happens when you don’t allow building in the green belt. Figure 1 shows how the green belt surrounds Cambridge, making it more difficult for the city to build the homes it needs. A response to this in the 1990s was to jump the green belt and build a new settlement on green field land 9 miles to the west of the city. Cambourne was born. According to the last census there were 10,000 people living there in 2021. 

Figure 1: Cambridge is surrounded by green belt 

Source: gov.uk 

Cambridge is well known for its use of cycling. According to the 2011 census (the last reliable source of commuting statistics, although the less reliable 2021 data is remarkably similar), half of commuters walked or cycled to work. This is not the case in Cambourne. Building a settlement 9 miles from its largest local source of jobs doesn’t lend itself to active travel. Less than one in 10 commuters travelled by foot or bike, which wasn’t just behind the Cambridge average but behind the national average too (see Figure 2). 

Figure 2: Commuters from Cambourne are much more car dependent than those in Cambridge

It seems likely that had the homes built in Cambourne been put on the green belt that abuts against Cambridge then car usage for these homes would have been lower. And for those who do use cars, their journeys (for both work and for leisure) would be shorter. 

Fortunately, some more recent development has followed this principle. Both Cambridge and South Cambridgeshire have released small parcels of green belt to build at Eddington on the north west fringe and the biomedical campus in the south of the city. Future development of the city – something the national economy needs – should follow these principles to minimise the environmental impact of new homes. And those who are concerned about the environmental impact of development should be supportive of it. 

There is direct read across to the Government’s new towns and grey belt policies. Location is important for both. Grey belt land in an isolated location, or a poorly-connected new town, will have worse economic and environmental outcomes than an urban extension on green belt land. Both policies should not be influenced by the misleading ‘green belt’ tag.