We often imagine conservation unfolding in wild, far-flung landscapes, not in the middle of bustling cities. Urban environments can seem like the end of the road for nature, where even the trees appear weary, boxed into concrete pavements and gridlocked streets with a faint look of dismay.
But look a little closer and a different story emerges. On rooftops, in alleyways and through the tiniest cracks in the pavement, biodiversity is finding its way back in. Wildlife, it turns out, can thrive even in the heart of the metropolis. Cities, says Nathalie Pettorelli of the Zoological Society of London, aren’t just degraded wastelands where ‘real’ nature has been paved over. They’re ecosystems in their own right. The problem isn’t that they aren’t forests – it’s that we keep pretending that they should be.
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The city as an ecosystem
“If you frame our cities as ‘trash nature’, you never appreciate the nature of a city as an ecosystem in itself,” she says. “But if you accept the city is an ecosystem, the question then becomes: how do you make that ecosystem more biodiverse?”
Rather than comparing Hackney to the Highlands, imagine comparing it to a ‘better’ Hackney. Greener, messier and more connected, sheltering species that can roam and explore and enhance the ecosystem. A habitat with hedgehog highways and bird-friendly balconies, where what grows between the cracks isn’t merely tolerated but welcomed. If all the private gardens in London were linked up and allowed to rewild, you’d get a landmass about the size of the New Forest. Somewhere between the compost bins and patio chairs, the city becomes a national park in disguise.
The catch? It’s fragmented. A thousand microhabitats stranded among lines of fence panels and swathes of tarmac. If you’re a beetle or a slow, hopeful hedgehog, you need to move, set up a home, build a family. “Connectivity is vital,” explains Pettorelli. “The scale of the ecosystem is the whole city. It’s not about one garden – it’s about how all of them fit together.”
Connecting habitats
In the UK, initiatives such as Hedgehog Street encourage neighbours to link their gardens through small fence holes to allow for free movement. In Utrecht, the Netherlands, more than 120km of wildflower verges stitch together fragmented green spaces, providing continuous habitat for bees and butterflies. In Oslo, Norway, a ‘bee highway’ weaves through rooftops, parks and balconies to offer pollinators safe passage around the urban maze.
Wildlife bridges are another powerful tool for connecting habitats. The Netherlands is well known for pioneering ‘ecoducts’ – green overpasses that allow animals such as deer, boar and badgers to safely cross busy highways. In California, the Wallis Annenberg Wildlife Crossing is currently under construction. When finished, it will span an expansive 10 lanes of traffic and reconnect mountain lion populations fragmented by development. These crossings are bold symbols of a new ecological mindset.
Look out over a city and you’ll likely see naked rooftops, scaffolding, multi-storey car parks and empty office blocks. But these can all serve as wildlife habitat if we stop treating them as dead space. Nature-positive architecture is the growing trend of looking at how we design buildings that not only minimise impact on the environment but actively restore and enhance biodiversity, providing shelter, food and connectivity for wildlife. They incorporate natural elements such as green roofs and living walls, use sustainable materials, and integrate ecosystem services such as rainwater harvesting and water purification systems.
The idea – challenging though this may currently seem – is that buildings can have a net-positive benefit for nature across their entire life-cycle, from material extraction to final demolition. The UK Green Building Council, a charity formed in 2007, is developing a framework to help architects, planners and developers embed measurable biodiversity gains into building projects, bringing clear, actionable standards to the concept of ‘nature positivity’.
Biodiverse buildings
A building’s carbon footprint is often thought of in terms of the energy it uses once occupied. But long before the lights are turned on, a building has already made its mark. The extraction of raw materials and their manufacture, transport and assembly all generate emissions known as ‘upfront embodied carbon’. Unlike operational emissions, which can be reduced over time with upgrades and efficiencies, upfront emissions are locked in from the outset. Addressing this hidden, early footprint has become a priority in sustainable design.
Green roofs are nothing new, but whereas they were once created for aesthetic or economic reasons, we’re now understanding their huge ecological benefits. When designed well, green roofs act as mini-meadows in the sky, hosting everything from beetles to native orchids. They improve air quality (and, in turn, public health) and combat the urban heat-island effect, helping to mitigate climate change. Chicago City Hall’s green roof, for instance, created in the early 2000s, covers nearly 2,000m2 and comprises more than 150 species of plants. As well as attracting insects, temperatures in summer are nearly 7°C cooler than the surrounding rooftops.
Living walls offer another dimension of biodiversity. The Rubens at the Palace hotel in London boasts a vertical garden of more than 10,000 plants, designed to trap pollutants and provide nectar sources for pollinators. Bosco Verticale in Milan, Italy, supports more than 900 trees in its vertical forest towers. And, in Singapore, the Oasia Hotel’s plant-covered facade actively cools the building and attracts birds and insects.
Sedum, a hardy, drought-resistant succulent, is often used in green roofs for its easy maintenance. But without other species, it offers little to pollinators or birds. True biodiversity comes when these roofs are designed not just as features but as ecosystems, and are part of a broader picture of nature restoration.
“Green roofs and corridors have their place,” says Professor Jens-Christian Svenning, director at the Center for Ecological Dynamics in a Novel Biosphere at Aarhus University in Denmark, “but they should complement, not replace, efforts to expand wild urban areas.”
Svenning believes in citywide strategies: connecting patches of habitat, rethinking floodplains, planting for pollinators along tramlines. But we need small-scale interventions too, the personal touches that say ‘wildlife welcome’, such as bee bricks, birdboxes and hedgehog holes.
The future of green buildings
Once, the best you could hope for from a building was that it didn’t collapse or leak. Then we asked them to stop emitting carbon. Now we’re asking them to heal the planet. Yet it’s not as far-fetched as it sounds. A new wave of architects and material innovators are treating buildings less like fortresses and more like forests – structures that give back.
Take regenerative materials such as hempcrete. It’s made from hemp, lime and water. It’s breathable, insulating and incredibly good at storing carbon – twice as effective at sequestering CO₂ as a forest, according to some estimates. Plus, it grows like the clappers. According to Hemspan, a UK company specialising in hemp-based construction, 1ha of industrial hemp can absorb up to 11 tonnes of CO₂ annually.
Hempcrete is already being used in homes, schools and small commercial buildings across the UK, particularly in timber frame construction. The Enterprise Centre at the University of East Anglia is an example of a commercial building using hemp at scale, while Greencore Homes, which claims that its Springfield Meadows development in Oxfordshire is the UK’s most sustainable private residential property development site, uses hempcrete extensively in its superstructures as an alternative to other forms of insulation.
Greencore says that one of its most efficient homes, independently verified by global engineering consultancy WSP, achieved minus 278kg CO₂ e/m² (kg of CO₂ equivalent per square metre) in upfront embodied carbon. In other words, for every square metre of the home, the building’s structure has effectively removed 278kg of carbon dioxide. That’s better than net zero.
Nature's inspiration
But nature-positive design isn’t just about creating greener structures. It’s inspiring us to rethink how buildings behave, using nature for guidance. This is known as biomimicry: designing buildings that imitate termite mounds (for natural air conditioning), or forests (to store water), or coral reefs (to self-build and repair).
Take coral architecture. In Haiti, Vincent Callebaut’s visionary Coral Reef project proposes a self-sufficient, modular village built into the curve of a coral-like structure. Designed to house displaced communities, it aims to utilise solar energy, food production zones and green terraces. Similarly, in France, a student housing development mimics coral’s lattice structures in its facade, creating natural airflow and diffused light, while visually linking marine form with ecological function.
And what if a building could even self-heal, like a coral reef? Some architects are exploring this very idea. Experimental design labs are trialling materials that mimic the way coral regenerates and channels water, offering inspiration for facades that can clean themselves, regulate temperature and even adapt over time.
“It’s about asking how we can design like an ecosystem,” says architect and biomimicry pioneer Michael Pawlyn. “How can a building behave like a tree or a wetland, sequestering carbon, purifying air and creating habitat?”
The idea isn’t just to do a bit less harm – it’s to regenerate. Imagine a housing block that not only didn’t destroy habitat but created a new one. A housing block that stored water, cooled streets and had swifts nesting under its eaves. The wild city of the future might not look wild at all. But behind the walls and under the pavements, it’ll be teeming with life.
Emma Marris, author of Rambunctious Garden: Saving Nature in a Post-Wild World, and a leading voice in rethinking how we relate to urban nature, sees examples everywhere that show wildlife is making a comeback where it has the space to do so. “Spontaneous plants colonising flood zones, birds nesting in signage… some of the best urban nature is accidental,” she says.
Whether you’re planting sedum on a shed roof, lobbying for green corridors or simply leaving a patch of garden untidy, there’s space for everyone in the future wild city. Nature doesn’t need perfection – it just needs opportunity.
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Top image: green roofs incorporated into a Chinese scheme. Credit: Getty
