7 London boroughs are more than 25% green belt

London's beautiful green belt. Image of Rainham Marshes courtesy of Romfordian, via Wikimedia Commons.

Ask whether it's time to re-think Britain's green belts, as we often do in these parts, and you're likely to get a mixed response. Part of your audience – the younger, more urban, more-likely-to-be-private-tenants part – will cheer you on. But a significant minority will call you all sorts of names, accuse you of being in the pocket of the construction industry, and probably at some point blame immigration.

Such is life. But since this debate isn't going to go away any time soon, we thought it might be worth injecting some figures into it. Let’s consider the Metropolitan Green Belt which has restricted London’s growth since 1938.

There are 33 boroughs in London, of which no fewer than 19 have at least some protected Green Belt land within them. This chart shows the size of those 19 by area (total bar length), and the proportion of each which is designated as Green Belt (the bit that's, well, green). We’ve taken our data from government figures, hosted here.


The first thing that you notice is that Bromley is enormous. At around 150 km2, it takes up very nearly a tenth of the entire capital, and it's larger than the eight smallest boroughs put together. (These are all in inner London, so don't feature on the graph.)

The next thing you notice is that more than half of that vast south eastern borough is green belt land (to be exact, 52 per cent of it).

In all, there’s around 77 km2 of Green Belt in Bromley: enough to swallow the City, Kensington, Islington, Hammersmith and Hackney whole, and still have room for most of Tower Hamlets. That's an area that houses nearly 1m people.

We're not seriously suggesting putting that many people in the green fields of Bromley. We're just pointing out that you could. Look:

Bromley isn't the only large outer borough that is, quite literally, half empty. Up in the north east, Havering is actually even roomier, with nearly 54 per cent of its land classified as Green Belt. Again, you can see this on the map, which shows that huge swathes of the borough are effectively empty.

To the west, Hillingdon is 43 per cent empty, while another four boroughs are more than a quarter Green Belt.

The point we're getting at here is that there is a lot of land classified as Green Belt even within London. In all, it's more than a fifth of the capital's land area (22.4 per cent).

As you might expect, the neighbouring areas are often even more in the grip of the Green Belt. Here's the same chart, but this time showing counties:

Now, “green belt" is actually at times a misleading label. The name evokes beautiful rolling fields, and some of this land will live up to that image. But it also includes quarries, and scrubland, and golf courses, and pony clubs. Some of this land is of value to the community; some of it isn't.

Nonetheless, there are those who see it as inviolable – who squeal at any suggestion we should re-label it as anything other than green belt, or develop it to meet London's housing needs. People who imagine that giving up even one blade of grass will turn the entirety of England into Houston within weeks.

But what it is that terrifies them so remains a complete mystery to me, because they are winning, hands down. Between 2007 and 2010, London lost approximately 140 hectares of green belt land, but gained another 100 elsewhere. In total, then, it lost 40. For those who are keeping score, that's just over 0.1 per cent of all its green belt land.

And this, remember, is not 0.1 per cent of the entire green belt – it’s 0.1 per cent of the portion of the green belt which is contained within the official boundaries of the city. The green belt as a whole is approximately 15 times larger, and that isn’t going anywhere either.

It'd probably be foolish to scrap the green belt altogether, and simply let the construction industry let rip. But it's equally naive to imagine that this land is, and must always remain, inviolable.

London can build the extra homes that its population needs. We've more than enough space.


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.