Green infrastructure can cool our cities. So what are planners waiting for?

A living wall in action: Patrick Blanc's "Trussardi Cafe: Unexpected Garden" on display in Milan in 2008. Image: Getty.

Our cities are getting hotter, more crowded and noisier. Climate change is bringing more heatwaves, placing pressure on human health, urban amenity, productivity and infrastructure.

Urban residents naturally want to stay cool. Air conditioning is the usual choice, but it can be expensive to run. Air conditioning also adds carbon pollution, creates noise and can make outdoor spaces hotter.

So what else can we do to manage increasing urban heat? And who has the ability to act?

Urban planners are increasingly involved in developing and delivering urban greening strategies. While it seems like a “no brainer” to green cities, our international research shows that planners are not always comfortable with this idea.

However, green infrastructure – including street trees, green roofs, vegetated surfaces and green walls – is emerging as a viable way to help cities adapt to increased heat. Uptake of these technologies is slowly increasing in many cities around the world.

Green walls cooling a building in Singapore. Image: Tony Matthews.

The Australian government has recognised this trend. An agenda to green Australia’s cities is now in place. Stated aims include managing climate change impacts, reducing urban heat, improving urban well-being and increasing environmental performance.

This urban greening agenda is part of the Clean Air &Urban Landscapes hub, under the National Environmental Science Program.

Benefits of urban greening

The broadening appeal of green infrastructure is helped by the fact it offers multiple benefits.

For example, shading from strategically placed street trees can lower surrounding temperatures by up to 6℃, or up to 20℃ over roads. Green roofs and walls can naturally cool buildings, substantially lowering demand for air conditioning. Green infrastructure can also provide habitat for wildlife, recreational opportunities for people, better management of stormwater runoff and improved urban aesthetics.

Street trees and green walls helping to reduce urban temperatures. Image: Tony Matthews.

Hard surfacing, including concrete, asphalt and stone, is common in cities. It can increase urban temperatures by absorbing heat and radiating it back into the air. Green infrastructure can minimise this difficulty, as it better regulates ambient air temperatures. Foliage allows local cooling through evapotranspiration, where plants release water vapour into the surrounding atmosphere.

Why planners are cautious

Our research examined urban planners' attitudes towards green infrastructure use in Australia, England and Ireland. We found that planners are broadly aware of green infrastructure as an urban intervention. They understand its use, application and capacity to provide multiple benefits, especially in terms of managing urban heat.

The planners we interviewed, while recognising the potential value of green infrastructure, strongly cautioned that delivering the technology can be an uncertain process. The biggest barrier cited was that planning departments are not experienced with green infrastructure.

Put simply, they tend to avoid it because it has not traditionally featured on planning agendas. Like any new planning endeavour, green infrastructure can create institutional, legal, economic, social and environmental challenges.


Some of the biophysical challenges associated with green infrastructure delivery are novel. Choosing appropriate forms of vegetation, for example, may be difficult. Decisions must be made based on prevailing climactic conditions, drainage capacity and species growth patterns.

Will root systems damage buildings or underground utility networks? Might trees topple during storms and damage houses? Are roofs strong enough to support a rooftop garden? Planners may not be able to answer these questions, which creates a need for external experts to advise them.

Our findings also highlight socio-political factors as barriers. These include governance concerns such as the political context in which planning decisions are made.

Management issues also feature. Chief among these are government commitments to budget for green infrastructure delivery and management.

Planners are also wary of public involvement. They know that public sentiment about green infrastructure can be influenced by perceptions of modified access, changed use, or loss.

What can be done?

The urgency for providing urban green infrastructure increases as climate change makes our cities hotter. Our research suggests the principal task for planners is to overcome embedded practices and to accept green infrastructure as an emerging but permanent urban feature.

This will not be easy. For example, a decision to use a road easement for green infrastructure may require multiple meetings with other government departments, utility companies and residents. Planners will need to coordinate these, manage stakeholder expectations and ensure cost sharing where necessary.Legal, economic, social and environmental issues will require innovative solutions.

Planners will increasingly be tasked to deliver green infrastructure in cities. They will need to be clear on its value, be prepared to lead its delivery and learn from new challenges and solutions encountered along the way.

But urban residents all over the world stand to benefit if planners can successfully meet this challenge – particularly as hotter temperatures threaten urban comfort and habitability.The Conversation

Tony Matthews is a lecturer in urban & environmental planning, and Jason Byrne an associate professor in environmental planning, at Griffith University, Queensland.

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

 
 
 
 

Leeds is still haunted by its pledge to be the “Motorway City of the Seventies”

Oh, Leeds. Image: mtaylor848/Wikimedia Commons.

As the local tourist board will no doubt tell you, Leeds has much to be proud of: grandiose industrial architecture in the form of faux-Egyptian temples and Italian bell-towers; an enduring cultural legacy as the birthplace of Goth, and… motorways. But stand above the A58(M) – the first “urban motorway”  in the country – and you might struggle to pinpoint its tourist appeal.

Back in the 1970s, though, the city council was sufficiently gripped by the majesty of the motorways to make them a part of its branding. Letters sent from Leeds were stamped with a postmark proudly proclaiming the city's modernity: “Leeds, Motorway City of the Seventies”.

Image: public domain.

During the 1960s, post-war optimism and an appetite for grand civic projects saw the rapid construction of motorways across England. The construction of the M1 began in 1959; it reached Leeds, its final destination, in 1968. By the early 1970s the M62 was sweeping across Pennines, and the M621 loop was constructed to link it to Leeds city centre.

Not content with being the meeting point of two major motorways, Leeds was also the first UK city to construct a motorway through the city centre: the inner ring road, which incorporates the short motorway stretches of the A58(M) and the A64(M). As the council put it in 1971, “Leeds is surging forward into the Seventies”.

The driving force behind Leeds' love of motorways was a mix of civic pride and utopian city planning. Like many industrial cities in the North and Midlands, Leeds experienced a decline in traditional manufacturing during the 1960s. Its position at the centre of two major motorways seemed to offer a brighter future as a dynamic city open for trade, with the infrastructure to match. In response to the expansion of the roads, 1970s council planners also constructed an elevated pedestrian “skywalk” in an attempt to free up space for cars at ground level. Photos of Leeds from that time show a thin, white walkway running through blocky office buildings – perhaps not quite as extensive as the futuristic urban landscape originally envisaged by planners, but certainly a visual break with the past.

Fast forward to 2019 and Leeds’ efforts to become a “Motorway City” seems like a kitsch curiosity from a decade that was not always known for sustainable planning decisions. Leeds’s historic deference to the car has serious consequences in the present: in February 2019, Neville Street – a busy tunnel that cuts under Leeds station – was found to contain the highest levels of NO2 outside London.

City centre planners did at least have the foresight to sink stretches of the inner motorways below street level, leaving pedestrian routes largely undisturbed. Just outside the centre, though, the roads can be more disruptive. Sheepscar Interchange is a bewildering tangle of arterial roads, Armley Gyratory strikes fear into the hearts of learner drivers, and the M621 carves unsympathetically through inner-city areas of South Leeds with pedestrian access restricted to narrow bridges that heighten the sense of a fragmented landscape.

 

Leeds inner ring road in its cutting. Image: author provided.

 

The greatest problem for Yorkshire's “Motorway City” in 2019, however, is not the occasional intimidating junction, but the complete lack of an alternative to car travel. The dire state of public transport in Leeds has already been raised on these pages. In the early 20th century Leeds had one of the most extensive tram networks in the country. The last lines closed in 1959, the same year construction began on the A58m.


The short-sightedness of this decision was already recognised in the 1970s, as traffic began to build. Yet plans for a Leeds Supertram were rejected by successive Conservative and Labour governments unwilling to front the cost, even though smaller cities such as Newcastle and Sheffield were granted funding for light transport systems. Today, Leeds is the largest city in the EU without a mass transit system. As well as creating congestion, the lack of viable public transport options prevents connectivity: the city's bus network is reasonable, but weaker from East to West than North to South. As a non-driver, I've turned down jobs a short drive away that would be a logistical impossibility without a car.

Leeds' early enthusiasm for the motorway was perhaps premature, but there are things we can learn from the 1970s. Whatever else can be said about it, Leeds' city transport strategy was certainly bold – a quality in short supply today, after proposals for the supertram were watered down to a trolleybus system before being scrapped altogether in 2016. Leeds' rapid transformation in the 1960s and 70s, its grandiose visions of skywalks and dual carriageways, were driven by strong local political will. Today, the long-term transport strategy documents on Leeds City Council's website say more about HS2 than the need for a mass transit system within Leeds itself, and the council has been accused of giving up the fight for light rail and trams.

Whilst central government's refusal to grant funds is the greatest obstacle to Leeds' development, the local authority needs to be far more vocal in demanding the transport system the city deserves. Leeds' desire to be the Motorway City of the Seventies might look ludicrous today, but the political drive and utopian optimism that underpinned it does not.