Words by Joey Gardiner
Bringing nature into cities is hardly a new idea. In fact, it has swung in and out of vogue for more than a century, ever since Victorian social reformer Ebenezer Howard published what became the Garden Cities of To-morrow manifesto in 1898. Prompted by the squalid, polluted and dangerous environment faced by Victorian city dwellers and their growing alienation from the natural world, Howard’s idea was simple: to create places that brought together the best of urban and rural — homes surrounded by nature, but close to work and shops.
Despite all of the improvements since Victorian times, we still face challenges not that different from those that Howard was seeking to overcome. But now the stakes, in terms of mankind’s survival on the planet, are significantly raised.
"The World Health Organization estimates that, worldwide, 7 million people die each year from the effects of air pollution"
On the one hand, a compelling body of evidence suggests that cities remain dangerous places for people to live. The World Health Organization (WHO) estimates that, worldwide, 7 million people die each year from the effects of air pollution, with nine out of ten of us breathing air that breaches safe limits. The US government says excessive urban heat kills more people each year than all other weather-related disasters. Meanwhile, cities’ untold expanses of asphalt make them liable to floods that threaten lives and damage property, overwhelming water treatment facilities and sending raw pollution into rivers. As Pascal Mittermaier, global cities managing director at conservation charity The Nature Conservancy (TNC), says: “Many cities are becoming really toxic, dangerous and even deadly places to live.”
At the same time, and as a direct consequence of man’s activity, nature is being wiped out at a frightening and unprecedented rate. The scientific consensus is that habitat loss, man-made chemicals and climate change are together triggering a mass extinction event as severe as anything since the demise of the dinosaurs.
One recent global study of insects — essential for the proper functioning of all ecosystems — found populations to be collapsing at a rate that could see most species wiped out by the end of the century, with 40% already under threat.
In response to both of these challenges, a broad movement has emerged that, like Howard, is dedicated to bringing nature back to the places where most people live. Going by tags including ecological urbanism and biophilic urbanism, practitioners say greening cities can make them cooler, cleaner, healthier and more inspiring places, while helping to redress the collapse in biodiversity. Architects, landscape architects, engineers and ecologists inspired by this idea are working to deliver it in practice. But, with urban space at a premium, public and private clients need to be persuaded that there’s something in it for them. And questions remain over whether the perceived tensions between economic drivers, human needs and the natural world can ever be neatly resolved.
A diversity of benefits
The claims made in favour of greening cities are wide-ranging and backed by scientific evidence (see table, overleaf). The right kind of greenery can stop urban flooding by storing water; significantly reduce air pollution by filtering out harmful particulates; and cool cities, thereby reducing deaths during heatwaves. If that weren’t enough, green urbanists also claim psychological and social benefits such as reductions in stress and the promotion of community, as well as the economic boost of rising property prices and letting rates.
And that’s before the benefits to the natural world itself. Bill Reed, principal at consultant Regenesis and one of the most “deep green” urban practitioners, argues that by connecting people with nature and with our role in supporting the evolutionary health of natural systems, he “helps people fall in love with life”. Such is the enthusiasm, it’s tempting to wonder what urban greening can’t achieve.
“We need to move beyond nature as decoration, to an understanding that living systems have an integral role to play in our health”Bill Reed, Regenesis
Much of the rationale stems from the concept of “ecosystem services”. The idea behind this ecologists’ jargon is an important one: that nature provides a huge range of services to people — from provision of food and raw materials, to cleaning air and water, to bringing beauty and joy — that have a value, even a calculable monetary one. Hence, according to the Natural Capital Forum, street trees in California provide a flood and “atmospheric regulation” service to the US state worth US$1bn a year, while Mexico’s mangrove forests are worth US$70bn a year in storm protection, fishery support and tourism.
The services provided are endless. A Swedish study, for example, found that Eurasian Jays provide a US$10,000 per hectare oak tree planting service to forestry managers, simply by burying and subsequently forgetting about acorns. Globally, the value of services provided has been estimated at more than US$100tn, twice global GDP.
Considered in this way, it’s clear that many cities are now in dire need of these services. TNC’s Mittermaier says: “The way we’ve designed cities, they’re reaching breaking point. Nature can contribute to making them more resilient and healthier places.” Increasingly, city leaders are turning to nature to solve problems — in Philadelphia, for example, more than 400 separate pieces of green infrastructure have been laid down as part of a multibillion-dollar effort to manage run-off during heavy rainfall. A similar approach has been taken in Copenhagen, where parks and gardens are used for passive water storage.
Matthew Jessop, technical director for landscape and urban design at WSP, says they are working on projects from Los Angeles to Longbridge in the UK to re-wild culverted rivers. Emelie Arnoldsson, creative director at WSP in Sweden, which has recently integrated an ambitious landscaping scheme into the Juvelen office project in Uppsala, says the benefit in terms of tackling stormwater is often “the easiest way to sell bringing nature in” to prospective clients.
But flood risk is not the only driver. A string of cities from Portland, Oregon to Singapore have now declared themselves to be “Biophilic Cities”, harnessing nature to make residents happier, healthier and wealthier. In Singapore, developers must replace 100% of any green cover lost elsewhere in the development, resulting in the widespread conversion of roofs to gardens in the sky. The movement is supported by those concerned about the mental health consequences of city dwellers’ ever-diminishing connection with nature, famously characterized by author Richard Louv as nature-deficit disorder. Tim Beatley, a University of Virginia academic and founder of the Biophilic Cities movement, says greening urban environments can provide the natural context “essential for leading a happy and sustaining life”.
“The evidence is that the cost-benefits of all this are really strong,” says Tom Butterworth, technical director for biodiversity at WSP in the UK, where the government is proposing that all development must deliver a “biodiversity net gain”. And yet investing in green infrastructure is far from being the norm. The problem for developers, says Butterworth, is that not all of these benefits come back to them. “Yes, good infrastructure might raise prices a bit, but it’s unlikely to cover the cost of putting in the infrastructure, while the health and wellbeing benefits will play out for the residents over the long term.” It’s not just private developers who face this problem — in a period of constrained spending in many countries, public funders may also require direct returns from investments.
This tension is amplified in high-value urban environments, where there is huge pressure to make a site as economically productive as possible. In prime central London, for example, residential space can sell for up to £3,000 per ft2, which makes it extremely difficult to make green infrastructure pay. As Yun Hye Hwang, assistant professor of landscape architecture at the National University in high-density Singapore, puts it: “In a compact city, there is just less land available for nature such as woodlands and other forms of unmanaged greenery. The scarcity of land is a big challenge for landscape planners.”
There are, however, ways around this conundrum. One of Butterworth’s colleagues, Jenny Merriman, natural capital lead at WSP in the UK, has been collating evidence of the direct financial benefits to developers of green infrastructure, defined as a strategic network of environmental features delivering a wide range of ecosystem services. The work is at an early stage, but Merriman says it’s already clear the advantages go beyond small sales premiums. “The evidence suggests there are real cost savings to business. For example, better incorporation of nature’s value at the design stage means projects can navigate the planning process more efficiently, which has a huge knock-on in terms of time and resource.”
Meanwhile, Clare Warburton, principal green infrastructure adviser at UK government agency Natural England, is exploring ways to measure the “invisible” benefits of green infrastructure. She is leading the development of a tool, called the Eco-metric, designed to robustly compare provision of ecosystem services, as part of a coalition including Oxford University and WSP (see box, below). “There’s been a huge amount of interest in testing this tool, because of the way it allows you to capture the wider benefits your development will provide,” she says. And that means it can help to build the business case: “You can demonstrate and describe the wider benefits that investment in nature delivers for people and places, as well as for wildlife.”
The measure of nature: new tool will help to quantify the services it provides
A group of UK academics, developers, consultants and government agencies are developing a tool to measure ecosystem services. With the UK government planning to require a “biodiversity net gain” on all new developments, the Eco-metric tool would be able to show the wider benefits of any given proposal.
The work, due to be published later this year, is being led by government advisory body Natural England and the University of Oxford, with input from WSP among others. The idea is that the tool scores the services provided by nature in a given place — anything from water supply, air quality, pollination and carbon storage to “sense of place” — to produce a metric that is simple and transparent yet scientifically robust. This will allow a detailed benchmark of an existing site to be compared with what is due to replace it, allowing developments to be tailored to suit local priorities, be they flood mitigation or recreation.
Alison Smith, senior research associate at Oxford’s Environmental Change Institute, says this will give developers a way to demonstrate how sites have been designed to benefit people and nature in planning discussions. In a future where they could be required to contribute to off-site biodiversity-enhancing projects if a proposed scheme cannot deliver a net gain on site, this metric could be used to design better offsetting projects that benefit local communities as well as the environment.
Even if it is possible to persuade developers of the benefits of green infrastructure, there may be more subtle tensions at play that undermine the aims of ecological urbanism. For example, care must be taken that this agenda doesn’t become the pretext for creating yet more car-based suburban developments (ironically inspired by Howard’s Garden Cities), which grant residents big green spaces and generous gardens, but fail on climate change grounds.
Strong evidence suggests that, if greenhouse gas emissions are to be reduced, cities need to be compact enough to be walkable and support public transport. Biophilic Cities’ Beatley says any desire to bring in nature mustn’t compromise overall development density. “Compactness remains a starting point. Sprawl is a major destructive force. Part of a biophilic city is about its ecological footprint. If you’ve got a large consumptive footprint that is destroying nature, the city is not biophilic.”
The pressure to make every inch pay means prioritizing green infrastructure that can deliver multiple benefits from a single intervention, using the economic benefit as “a Trojan horse for doing lots of other great things”, as WSP landscape architect Jessop puts it. For example, a piece of flood water management infrastructure can also be a park, as well as improving air quality.
The trouble is that, as Butterworth points out, “combining these things is not something engineers are trained to do”. Experts say that doing this properly means bringing the landscape architect and ecologist in as the project is being conceived, rather than simply to fill in the leftover spaces. They must work with other disciplines to consider not just what green space will look like, but also — in an engineering and an ecosystem sense — what it will do.
Danish architect SLA, a pioneer of “wild” landscaping on various European developments, counts anthropologists, sociologists and biologists among its staff. “The reason to bring nature in is because it is beautiful, it is an amenity for people,” says partner Rasmus Astrup. “It’s the pleasure you get when you walk around in it. But it also has a performative value, it solves challenges, be it stormwater or extreme heat.”
With both biodiversity and a desire to minimize maintenance costs in mind, landscaping in cities is taking a new form: less manicured and much less dependent upon planting imported species unsuited to local conditions. The idea is that this fosters ecosystems that can sustain themselves to develop naturally, rather than environments that require constant intervention.
This is a long way from the common conception of a wild environment. On SLA’s recent Novo Nordisk project, the firm created a “wild” landscape around a corporate headquarters which dealt on site with all of the stormwater that might be generated, despite being in just a few centimetres of soil, above a car park for 400 cars. SLA’s Astrup says: “It’s a new typology of nature. It requires biodiverse plantings, and we don’t maintain it as you would traditionally — it’s very different to a beautiful lawn. But it’s not truly wild — we decided the species. It’s like we kickstarted nature.”
“If you don’t work with native species, then you can’t reduce heat in a sustainable manner”Rasmus Astrup, SLA
Dutch evolutionary biologist Menno Schilthuizen, a professor at Leiden University and author of the 2018 book Darwin Comes to Town, says the best interventions make use of those species that are already succeeding in adapting to urban environments. “We should create spaces for them to settle and colonize naturally, rather than ‘create’ ecosystems and plant them as complete mixtures,” he says. This may mean eschewing much-promoted ideas such as “green walls” that often require irrigation, in favour of materials such as the “living concrete” being piloted by University College London’s Bartlett School of Architecture. This is designed to be bio-receptive, an “architectural tree bark” that can be easily colonized by airborne algae, moss and lichen spores. Schilthuizen says: “Buildings can be built from novel materials that allow insects and small plants to settle without compromising the structure and function of that building.”
This new form does not suit everyone’s idea of what nature in cities should be. In many parts of the world, the use of non-native species, often in Western-influenced formal gardens with lawns, carries connotations of power and status. SLA’s Astrup has experienced this with a commission in the Middle East, where the strong desire was for non-native plantings that would have required a huge amount of irrigation to sustain. “If you don’t work with native species, then you can’t reduce heat in a sustainable manner, and you need a tonne of water. If you work with what’s locally available, the maintenance cost is not as high, and you’re celebrating your own culture,” he says.
For Regenesis’ Reed, too much green infrastructure is about simply reducing the level of harm caused, rather than actively improving the world. The scale of the global environmental challenge means that many efforts, however positive and well-intentioned, ultimately “are not going to be enough” to stave off environmental catastrophe. And there is, of course, the risk that city greening becomes more about public perception than actually making a difference. “We need to move beyond nature as decoration to the understanding that all of these living systems have an integral role to play in our health,” he says.
Indeed, in Reed’s mind, the biophilia movement and emphasis on ecosystem services may even be obstacles, putting the focus on how humans can benefit, rather than the interrelationship between natural and human systems. “The biophilia movement can be seen as anthropocentric. It’s often about what nature can do for me, which is half the story. We also need to do for nature. It’s not about ‘impact’, it’s about ‘reciprocity’.”
Biophilic Cities proponent Beatley rejects this interpretation, contending that the movement is just as much about man’s impact on nature as nature’s impact on man. True or not, there is little doubt that increasing biodiversity for its own sake is a difficult sell — however terrifying the scientific data. “With climate change there’s an obvious target to aim for,” says WSP’s Merriman. “But it’s very hard with biodiversity because it’s not so tangible.”
So, what are the prospects for developing a more profound urban ecology? Reed says it is possible to galvanize action towards truly radical engagements and interactions — but only where clients and communities come together to jointly regenerate places based on a deep understanding of the local ecology. Cities, he says, can be “brought back to civility and high quality of life through paying attention to the unique human and natural patterns in each unique place”.
If that may sound a little New Age for some, Reed is not alone in sensing the limit of mainstream market mechanisms to address biodiversity in a genuinely effective way. WSP’s Butterworth makes the point that with regulation, government has the power to change the financial equations of development. “As soon as doing something becomes a requirement,” he says, “then the cost isn’t born by the developer, instead it just comes off the price of the land.” This is topical in the UK, given the proposal to enforce a biodiversity net gain on developments as a requirement of the planning system.
Even more fundamental would be a financial system that genuinely takes account of everything nature provides — something the concept of natural capital aims to put right. “We have to change the mindset that the environment is a cost,” argues Merriman. “Our current economic system makes it look like it makes sense to do certain things, simply because the environment is not factored in. We’ve got to change the system to recognize that development requires a healthy environment.”
The question is, can we do it in time?