Here's why solving London's housing crisis will mean rethinking the green belt

London from above. Image: Getty.


So screams the front page of yesterday's Evening Standard. The crisis in question, predictably, is the one about housing, or more specifically the lack of it.

The story concerns a report commissioned by housing charity Shelter and written by consultancy Quod; and the Standard's headline is accurate, as far as it goes. But it doesn't go very far, and the report's reasoning is a bit more complicated than the paper implies. (CityMetric, of course, would never sex up a headline in an attempt to grab readers’ attention.)

So, for your delectation, here's how our take on what the report says.

Choices, choices

The report, written by Quod director and occasional CityMetric map warbler Barney Stringer, starts out by noting the expert consensus that London needs to build 50,000 homes a year to meet demand for housing. At the moment, it’s consistently somewhere under half that. That's probably not the only reason why renting a small flat in zone 2 for a year now requires you to sell the next three generations of your family into slavery, but it's be naive to imagine it isn't a factor.

So, we need to build more, which, since houses can't hang in the air like balloons, means finding more places to build them. The report lays out a number of options:

• Tall buildings

• Greenbelt

• Garden Cities

• Estate redevelopment

• Adding density to the suburbs

• Transport corridors

• High density town centres

As well as the mysterious

• Other options?

Thanks to the laws of physics, though, we really only have three choices: build up, build out, or build in derelict areas that are effectively empty at the moment ("brownfield" land). For obvious reasons everyone wants to start with the latter.

There's just one tiny problem:

There isn't enough brownfield

Brownfield doesn't actually mean "derelict", but rather "land that has previously been developed". You know your home, where you live? That's brownfield. If you have a garden, that was brownfield, too, until recently (they've now changed the rules).

In fact, unsurprisingly, the vast majority of land in London is used for something:

A map, courtesy of Quod. Click to expand.

It's really only the pink areas on this map that are open to redevelopment:

Click to expand.

And, to quote Quod’s report:

About half of non-housing brownfield land that is currently in employment uses – the half that is most suitable for redevelopment – is already earmarked for change in the Mayor’s Opportunity Areas. Tens of thousands of homes are being built in places such as Kings Cross, Stratford and Nine Elms.

To sum up, building more on brownfield means demolishing stuff that's already there and putting it somewhere else. Or it means spending money on decontaminating ex-industrial land, or on "land assembly" (buying up enough small patches until you’ve got one big enough to be worth redeveloping). It's rarely an easy solution, and we’re already doing the bits that are relatively easy anyway.

As a result, the private sector has never managed to build more than 18,000 homes a year on London's brownfield land. Which isn't close to being enough. So, if we’re going to fix this mess, we need to look at other options

Build up

Actually, that phrase is a bit of an over-simplification for a range of options that involve "fitting more stuff into the city as it stands".

Building up could mean tower blocks. London isn't the low-rise city of the imagination...

Click to expand.

...and as many as 28,000 London homes are on the 10th floor or higher.

But a lot of people don't much fancy living in tower blocks. And pressure groups like More Light More Power and the Skyline Campaign show there's significant public opposition to them, too. So it's unlikely that solving London's housing crisis will mean turning the whole place into Manhattan.

There are other ways of squeezing more people into existing housing areas. We could redevelop housing estates:

Click to expand.

That's good, because the public sector already owns the land and it tends to have good transport links. But to quote Quod’s report, the problem here is... redevelopment is not a quick or easy solution. Good estate renewal takes many years (decades even) and a great deal of co-operation and effort. It also requires significant investment

The government has promised £140m to redevelop 100 estates nation wide. Quite apart from the difficulty of turfing people out of their homes so you can rebuild them, that does not count as "significant investment".

Or perhaps we could densify the suburbs:

Click to expand.

This sounds pretty positive: 20 per cent of London's population occupies 40 per cent of its residential land. Increase the number of people living in those areas by 10 per cent, and you could get 75,000 homes.

The problem here is that those suburbs are largely privately owned, in the form of nice little semi-detached houses. The government has limited power to compel residents to flog their land to developers, and even if most of a street were up for it, there's no guarantee everyone would be. What's more, the lowest density areas tend to be in the outer boroughs...

Click to expand.

...which are least likely to favour new homes, and also quite likely to be swing voters. Great.

So that leaves...

Building out

London could meet its housing need through new garden cities. But that means imposing new buildings on communities a long way from anywhere the mayor actually has power over, in towns and rural areas that probably have housing crises of their own to contend with. And it means forcing people to make longer commutes, damaging their quality of life and the environment all at the same time.

Luckily, there is an alternative. More than a fifth of Greater London (22 per cent) is classified as green belt. Fourteen London boroughs have more green belt than residential land. And while most of it is pretty inaccessible at the moment...

The accessibility of London's green belt. Higher numbers are better. Click to expand.

...the value of that land goes through the roof the minute planning permission is granted. If local authorities could capture that uplift, they could pump the money back into vital transport infrastructure.

This is why the topline of the report is that building on green belt has to be part of the mix. It's where the Standard got their headline from. Here’s the key passage:

Before the metropolitan Green Belt was established London saw unprecedented rates of development. Almost one in five of London’s current homes were built in a single ten-year period just before the Second World War. A much smaller and more controlled release of appropriate bits of Green Belt could be an effective way to deliver substantial numbers of new homes.


There is a legitimate debate about whether London’s Green Belt could be better managed, ensuring the protection of beauty and public access as well as providing new homes. The new Mayor will need to take a pragmatic rather that absolutist view.

But that, at the moment, is where it all falls down. All four of the major party candidates (Labour's Sadiq Khan, the Tories' Zac Goldsmith, the Lib Dem Caroline Pidgeon and the Green Sian Berry) have ruled out even touching the green belt. Given the public support for keeping it in tact, that isn't an irrational thing to do.

Nonetheless, a commitment to protecting London's green belt, come what may, is also a commitment to not solving London's housing crisis. Goldsmith and Khan may talk about protecting the green belt while campaigning. But will the next mayor be brave enough to break their promise and do the right thing in office?

Because we’re suckers for this stuff, we'll be publishing more on this report, written by Quod's Barney Stringer himself, later this week.

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How bad is the air pollution on the average subway network?

The New York Subway. Image: Getty.

Four more major Indian cities will soon have their own metro lines, the country’s government has announced. On the other side of the Himalayas, Shanghai is building its 14th subway line, set to open in 2020, adding 38.5 km and 32 stations to the world’s largest subway network. And New Yorkers can finally enjoy their Second Avenue Subway line after waiting for almost 100 years for it to arrive.

In Europe alone, commuters in more than 60 cities use rail subways. Internationally, more than 120m people commute by them every day. We count around 4.8m riders per day in London, 5.3m in Paris, 6.8m in Tokyo, 9.7m in Moscow and 10m in Beijing.

Subways are vital for commuting in crowded cities, something that will become more and more important over time – according to a United Nations 2014 report, half of the world’s population is now urban. They can also play a part in reducing outdoor air pollution in large metropolises by helping to reduce motor-vehicle use.

Large amounts of breathable particles (particulate matter, or PM) and nitrogen dioxide (NO2), produced in part by industrial emissions and road traffic, are responsible for shortening the lifespans of city dwellers. Public transportation systems such as subways have thus seemed like a solution to reduce air pollution in the urban environment.

But what is the air like that we breathe underground, on the rail platforms and inside trains?

Mixed air quality

Over the last decade, several pioneering studies have monitored subway air quality across a range of cities in Europe, Asia and the Americas. The database is incomplete, but is growing and is already valuable.

Subway, Tokyo, 2016. Image: Mildiou/Flickr/creative commons.

For example, comparing air quality on subway, bus, tram and walking journeys from the same origin to the same destination in Barcelona, revealed that subway air had higher levels of air pollution than in trams or walking in the street, but slightly lower than those in buses. Similar lower values for subway environments compared to other public transport modes have been demonstrated by studies in Hong Kong, Mexico City, Istanbul and Santiago de Chile.

Of wheels and brakes

Such differences have been attributed to different wheel materials and braking mechanisms, as well as to variations in ventilation and air conditioning systems, but may also relate to differences in measurement campaign protocols and choice of sampling sites.

Second Avenue Subway in the making, New York, 2013. Image: MTA Capital Construction/Rehema Trimiew/Wikimedia Commons.

Key factors influencing subway air pollution will include station depth, date of construction, type of ventilation (natural/air conditioning), types of brakes (electromagnetic or conventional brake pads) and wheels (rubber or steel) used on the trains, train frequency and more recently the presence or absence of platform screen-door systems.

In particular, much subway particulate matter is sourced from moving train parts such as wheels and brake pads, as well as from the steel rails and power-supply materials, making the particles dominantly iron-containing.

To date, there is no clear epidemiological indication of abnormal health effects on underground workers and commuters. New York subway workers have been exposed to such air without significant observed impacts on their health, and no increased risk of lung cancer was found among subway train drivers in the Stockholm subway system.

But a note of caution is struck by the observations of scholars who found that employees working on the platforms of Stockholm underground, where PM concentrations were greatest, tended to have higher levels of risk markers for cardiovascular disease than ticket sellers and train drivers.

The dominantly ferrous particles are mixed with particles from a range of other sources, including rock ballast from the track, biological aerosols (such as bacteria and viruses), and air from the outdoors, and driven through the tunnel system on turbulent air currents generated by the trains themselves and ventilation systems.

Comparing platforms

The most extensive measurement programme on subway platforms to date has been carried out in the Barcelona subway system, where 30 stations with differing designs were studied under the frame of IMPROVE LIFE project with additional support from the AXA Research Fund.

It reveals substantial variations in particle-matter concentrations. The stations with just a single tunnel with one rail track separated from the platform by glass barrier systems showed on average half the concentration of such particles in comparison with conventional stations, which have no barrier between the platform and tracks. The use of air-conditioning has been shown to produce lower particle-matter concentrations inside carriages.

In trains where it is possible to open the windows, such as in Athens, concentrations can be shown generally to increase inside the train when passing through tunnels and more specifically when the train enters the tunnel at high speed.

According to their construction material, you may breath different kind of particles on various platforms worldwide. Image: London Tube/Wikimedia Commons.

Monitoring stations

Although there are no existing legal controls on air quality in the subway environment, research should be moving towards realistic methods of mitigating particle pollution. Our experience in the Barcelona subway system, with its considerable range of different station designs and operating ventilation systems, is that each platform has its own specific atmospheric micro environment.

To design solutions, one will need to take into account local conditions of each station. Only then can researchers assess the influences of pollution generated from moving train parts.

The ConversationSuch research is still growing and will increase as subway operating companies are now more aware about how cleaner air leads directly to better health for city commuters.

Fulvio Amato is a tenured scientist at the Spanish National Research CouncilTeresa Moreno is a tenured scientist at the Institute of Environmental Assessment and Water Research (IDAEA), Spanish Scientific Research Council CSIC.

This article was originally published on The Conversation. Read the original article.