Is increasing population density the solution to the land-squeeze in successful cities?

Manchester. Could get some more people in there. Image: Getty.

The Centre for Cities' recent City Space Race report highlights a dilemma that most growing cities are currently facing: they need to build more houses and offices, but regulations and local political pressures restrict them from expanding, particularly when it comes to green belt development.

In theory, there is a simple way for cities to have their cake and eat it too. Increasing density — allowing taller buildings on the same space — should enable cities to provide more property space without having to expand outwards.

This idea is often the source of heated debate in public discussions about tackling the housing crisis in our most economically vibrant cities. But is increasing density the right solution for cities with high demand for land – and how viable is it in practice?

High average, low extremes

The UK is already a dense country. It has one of the highest average built-up densities — the population density of inhabited areas — across European countries.

But average national density is a blunt measurement of population versus land in a country and offers little insight into the variations across and within cities. When we look closer at UK cities, it’s clear that few urban neighbourhoods have the level of density found in other European cities. The densest square kilometre in the country, with a population of 20,000, is in the London neighbourhood of Maida Vale — an affluent area which doesn’t exactly fit the stereotype of an urban jungle.

In contrast, some urban areas on the continent exceed 50,000 inhabitants — for instance, the most populated square kilometre in Europe is in Barcelona with 53,000 inhabitants.

The chart below plots all square kilometre units that are populated with more than 10,000 inhabitants for a selection of countries. In the UK, 86 per cent of these areas have between 10,000 and 15,000 inhabitants, and the other 18 per cent have less than 20,000. By comparison, all other main European countries have areas exceeding 20,000 inhabitants, with Italy, France and Spain having a considerable share of very high-density neighbourhoods.

Source: Eurostat.

The benefits of population density

This means there is scope to increase density in UK cities, and in particular in residential neighbourhoods. This would have many benefits: not only would it allow cities to accommodate new residents without expanding, it would also improve cities’ transport accessibility and planning.

Let’s focus on this last point. Transport systems in denser cities are likely to be more efficient because they can reach a larger share of the population at lower costs. Consider Hong Kong, an extreme case of dense population settlement. Only 7 per cent of the working population commutes using their private car according to the Hong Kong statistics department.

In contrast, 33 per cent of Londoners travel to work by car (still a reasonable figure against international standards), while this group is bigger still in Liverpool (57 per cent of commuters), Manchester and Birmingham (64 per cent), as shown on our data tool.

High density in Hong Kong makes the transport network more efficient too: the metro network is short in length (210 km), and yet it serves 1.1m workers every day. In comparison, “only” 800,000 commuters use the London Underground, according to the 2011 census, despite the network being twice as long (402 km).

In other words, denser cities lead to better transport accessibility, and this, in turn, means better access to jobs, less traffic congestion and fewer carbon emissions. (As research by LSE cities shows, there is a clear negative correlation between urban population density and carbon emission per capita.)

The challenges of increasing density

As such, increasing population density clearly brings significant advantages. However, it is not easy to achieve, and there are two main reasons for this.

First, some local residents are concerned that densification will alter and threaten the nature and shape of their city, and this puts political pressure on councils not to act. That’s because densification is often amalgamated with high-rise buildings.

 But London does not have to become Hong Kong. If only 5 per cent of the capital’s built up area had the density of Maida Vale, it could host an additional 1.2m people, without the need to expand outwards.

Second, it is easy to forget the administrative and technical complexities of densification. In concrete terms — both literally and figuratively — densification means knocking down existing buildings to build new ones. This is time-consuming and it has a cost. Moreover, unless a city has in place an overarching plan to increase densification across its length and breadth, it will take decades for it to become more compact.


What should be done?

For growing cities to build more houses and commercial space, there are only two options: build up or build out.

Building up (densification) has many great benefits, but it is also difficult to deliver. To have a chance to happen, densification must be at the core of strategic planning policies and cities must have the necessary power, determination and leadership to bring it about. However, this is a long-term strategy, with benefits that will only be reaped in the long-term.

In the meantime, a number of cities have an urgent need to build more houses, and lack of action puts pressure on the existing stock, as highlighted in our report. Only building out (expanding) will enable them to respond to this need quickly enough. In most cases, this means that some green belt land must be released for development.

This is a difficult trade-off, but there is a middle ground between full densification and full expansion. For instance, cities could release plots of green belt land that are found within walking distance to an existing train station, and ensure that new developments have higher densities (in a Maida Vale rather than a Hong Kong style). This would allow cities to create a large number of homes on a small fraction of the land, limiting encroachment on the green belt and allowing easy transport access to the city.

Hugo Bessis is a researcher for the Centre for Cities, on whose blog this article originally appeared.

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“A story of incompetence, arrogance, privilege and power”: A brief history of the Garden Bridge

Ewwww. Image: Heatherwick.

Labour assembly member Tom Copley on a an ignominious history.

The publication last week of the final bill for Boris Johnson’s failed Garden Bridge has once again pushed this fiasco into the headlines.

As well as an eye-watering £43m bill for taxpayers for this Johnsonian indulgence, what has been revealed this week is astonishing profligacy by the arms-length vehicle established to deliver it: the Garden Bridge Trust. The line by line account of their spending reveals £161,000 spent on their website and £400,000 on a gala fundraising event, amongst many other eyebrow raising numbers. 

Bear in mind that back in 2012, Johnson promised that the bridge would be entirely privately funded. The bridge’s most ardent advocate, Joanna Lumley, called it a “tiara for the Thames” and “a gift for London”. Today, the project would seem the very opposite of a “gift”.

The London Assembly has been scrutinising this project since its inception, and I now chair a working group tasked with continuing our investigation. We are indebted to the work of local campaigners around Waterloo as well as Will Hurst of the Architects Journal, who has brought many of the scandals surrounding the project into the open, and who was the subject of an extraordinary public attack by Johnson for doing so.

Yet every revelation about this cursed project has thrown up more questions than it has answers, and it’s worth reminding ourselves just how shady and rotten the story of this project has been.

There was Johnson’s £10,000 taxpayer funded trip to San Francisco to drum up sponsorship for the Thomas Heatherwick garden bridge design, despite the fact that TfL had not at that point even tendered for a designer for the project.

The design contest itself was a sham, with one of the two other architects TfL begged to enter in an attempt to create the illusion of due process later saying they felt “used”. Heatherwick Studios was awarded the contract and made a total of £2.7m from taxpayers from the failed project.


Soon after the bridge’s engineering contract had been awarded to Arup, it was announced that TfL’s then managing director of planning, Richard de Cani, was departing TfL for a new job – at Arup. He continued to make key decisions relating to the project while working his notice period, a flagrant conflict of interest that wouldn’t have been allowed in the civil service. Arup received more than £13m of taxpayer cash from the failed project.

The tendering process attracted such concern that the then Transport Commissioner, Peter Hendy, ordered an internal audit of it. The resulting report was a whitewash, and a far more critical earlier draft was leaked to the London Assembly.

As concerns about the project grew, so did the interventions by the bridge’s powerful advocates to keep it on track. Boris Johnson signed a mayoral direction which watered down the conditions the Garden Bridge Trust had to meet in order to gain access to further public money, exposing taxpayers to further risk. When he was hauled in front of the London Assembly to explain this decision, after blustering for while he finally told me that he couldn’t remember.

David Cameron overruled the advice of senior civil servants in order to extend the project’s government credit line. And George Osborne was at one point even more keen on the Garden Bridge than Johnson himself. The then chancellor was criticised by the National Audit Office for bypassing usual channels in order to commit funding to it. Strangely, none of the project’s travails have made it onto the pages of the London Evening Standard, a paper he now edits. Nor did they under his predecessor Sarah Sands, now editor of the Today Programme, another firm advocate for the Garden Bridge.

By 2016 the project appeared to be in real trouble. Yet the Garden Bridge Trust ploughed ahead in the face of mounting risks. In February 2016, despite having not secured the land on the south bank to actually build the bridge on, nor satisfied all their planning consents, the Trust signed an engineering contract. That decision alone has cost the taxpayer £21m.

Minutes of the Trust’s board meetings that I secured from TfL (after much wailing and gnashing of teeth from the Trust itself) reveal that weeks beforehand Thomas Heatherwick had urged the trustees to sign the contract in order to demonstrate “momentum”.

Meanwhile TfL, which was represented at board meetings by Richard de Cani and so should’ve been well aware of the mounting risks to the project, astonishingly failed to act in interests of taxpayers by shutting the project down.

Indeed, TfL allowed further public money to be released for the project despite the Trust not having satisfied at least two of the six conditions that had been set by TfL in order to protect the public purse. The decision to approve funding was personally approved by Transport Commissioner Mike Brown, who has never provided an adequate explanation for his decision.

The story of the Garden Bridge project is one of incompetence, arrogance and recklessness, but also of privilege and power. This was “the great and the good” trying to rig the system to force upon London a plaything for themselves wrapped up as a gift.

The London Assembly is determined to hold those responsible to account, and we will particularly focus on TfL’s role in this mess. However, this is not just a London issue, but a national scandal. There is a growing case for a Parliamentary inquiry into the project, and I would urge the Public Accounts Committee to launch an investigation. 

The Garden Bridge may seem like small beer compared to Brexit. But there is a common thread: Boris Johnson. It should appal and outrage us that this man is still being talked about as a potential future Prime Minister. His most expensive vanity project, now dead in the water, perhaps serves as an unwelcome prophecy for what may be to come should he ever enter Number 10.

Tom Copley is a Labour member of the London Assembly.