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A city is not a tree, and nor is it an island: My call to arms for urbanists in an ecological crisis

Updated: Jul 14, 2020

Written by Henry Crabb (MSc Sustainable Urbanism)

Many of us have spent lockdown admiring a raucous spring, watching life bounce into full sound and colour. For me, the appearance of swifts, goldfinches, commas and common blues has been a source of joy between the stress of deadlines, health and hygiene. One day I even saw a pair of hunting Peregrine Falcons! When they dived, I knew - what else but the fastest animal on earth. They still bring me joy now, weeks later. Before coronavirus, I would have struggled to identify any of them and would have likely passed them without noticing. I now feel much closer to nature and I’m not alone, 71% of people in England believe that nature is more important to them since lockdown.

While we must be aware that corona-caused destitution can lead to nature’s plunder, lockdown has shown us just how strongly it can bounce back if given the time and space. We have seen examples all over the world, from mountain goats in Llandudno, to sea lions in Buenos Aires. Our reconnection with nature in the UK only strengthens our desire to help it prosper and, from this, we can gather real hope and momentum against the ecological crisis. According to the WHO, nature’s destruction is partly responsible for COVID-19. So to prevent another pandemic, deliver joy, and fight the ecological crisis, we must catch this momentum and encourage nature to bounce back stronger every year.

All across the UK, villages, towns and cities will play a crucial role as vital nodes of a new national Nature Recovery Network. This is my call to arms for all urbanists on the British Isles: a reminder of the crisis’ severity, the role played by urban areas and the powerful tools and opportunities we have at our disposal to help nature flourish, us included.

While spring bounces into summer, and life flourishes, we must consider the problem on a biological timescale and take an evolutionary perspective. After all, extinction is quite normal. More than 99% of all species that have ever lived are thought to have gone extinct. Usually, over time, this is balanced by the formation of new species (speciation) and a resilience that comes from high levels of genetic diversity. But, for many lineages, speciation is now limited by time and space: they can’t adapt fast enough to anthropogenic global heating, and geographical (allopatric) speciation is prevented by the homogenisation of land and a huge reduction in habitat ranges.

Scientists predict that the current extinction rate is possibly 100-1000 times the normal background rate and is accelerating. Troublingly, there have been forecasted losses of as much as 50% of all species globally by 2050, and this could be a serious underestimate due to the huge number of undescribed species. In the UK alone, 56% of species are in decline and 15% are under threat of extinction.

Look further back and you uncover much bigger losses. The UK is, in fact, already one of the most nature depleted countries in the world. Generation by generation, biodiversity shrinks and the baseline of what’s normal and ‘worth conserving’ shifts. This is highlighted by the frightening statistic that only 4% of mammals’ biomass are wild animals - the rest are humans and livestock. This is something that has happened slowly under our noses, but now it’s rapid and in plain sight. In these terms, conservation and sustainability are not enough. There must be restoration and regeneration, and they are beginning to get some traction.

A green and pleasant land

In its full summer bloom, it is hard to think of Britain as anything other than a green and pleasant land. And it is! But so much has been lost, and we are reeling from the effects. Much of Scotland was covered in the Caledonian Forest; swathes of it are now barren and maintained for grouse shooting. Beavers were once common and, an ecosystem engineer, helped store billions of gallons of water and create diverse habitats; they were hunted to extinction in the 16th century (though some have recently been reintroduced). And much of Wales, though beautiful and rugged, is often silent and devoid of a once rich biodiversity. Since the 1930s we have lost 97% of our wildflower rich grassland and many of our woodlands are ageing, unable to recover due to an imbalanced ecosystem full of deer. Like Aldo Leopold said: to the ecologically informed, we live in a landscape of wounds.

Nature has an immeasurable intrinsic value. But it is also invaluable to us. Its restoration has the potential to store carbon and prevent floods, repress pandemics and increase wellbeing. The path to recovery from coronavirus, global heating and biological annihilation is green, and the government is beginning to recognise it. Despite biodiversity spending being reduced by 34% since 2013, and Natural England’s budget being cut by 47% since 2010, the £640m Nature For Climate fund announced in March is a step in the right direction. Through this funding, Natural England and others can begin to develop a Nature Recovery Network, a commitment made in the government’s 25 year environment plan but not yet hardwired into policy.

A Nature Recovery Network is essential to heal our landscape’s wounds and build resilience for people and wildlife. It will realise expanded and reconnected habitats, welcome necessary ecological disturbance and restore ecosystem engineers like the beaver. Local Nature Recovery Strategies (LNRSs) will support its creation by requiring authorities to identify opportunities to expand and connect their wildlife habitats. The new agriculture bill will be especially important in rural areas, as farmers get rewarded for providing public goods such as biodiversity-borne flood protection on their land. However, we must be cautious: it takes time for wildlife to move into new habitats. The government’s “Project Speed” to “build, build, build” could undermine nature’s recovery if it happens too quickly for wildlife to proliferate, even if there are plans to provide space for it.

Plans and designs can take this into account on-site so that developments don’t rely solely upon the compensation of environmental losses in other areas through “net gain”. Urban designers, planners, architects, farmers and councils will all have an important role to play, ecologists will be more important than ever, and everybody will need to improve their ecological understanding. As the biological communities that most people experience, and places that foster extraordinary and unusual speciation, towns and cities will be vital nodes of this new network.

The city is not a tree, but nor is it an island

While the city is not a tree, nor is it an island. The connections with ‘nature’ that people form in cities will impact the treatment of wilder habitats beyond city boundaries, now and especially in an increasingly urban future. The resources that city dwellers require often come from beyond their bioregion, and children growing up in cities are at risk of developing ‘nature deficit disorder’. The thing is, cities are ‘natural’ and we are ‘nature’ – using the word ‘nature’ implies a separateness that can be harmful. We must rewild ourselves and fight the urge to be ‘tidy’ and compartmentalise or else we shun life.

London has proclaimed itself the first “National Park City” and urban greening is becoming more popular, but the rewilding of urban areas still needs impetus. Tidiness doesn’t conduce biodiversity: lawns, though green, are often termed “green deserts” due to their absence of biodiversity. But complaints to councils of untidy green spaces are frequent and housing managers can be resistant to wildness. Perhaps many of us are. Every year, much of London’s garden area is still converted to parking, decking, paving and sheds. With their great parks and gardens, the Victorians gave us our cities lungs, but since Corbusier and the advent of the artificial city, we seem to have developed a clinical disposition that we haven’t yet shook.

“It is more and more widely recognised today that there is some essential ingredient missing from artificial cities. When compared with ancient cities that have acquired the patina of life, our modern attempts to create cities artificially are, from a human point of view, entirely unsuccessful.”Christopher Alexander, A City is Not a Tree (1965)

The qualities of human vitality and richness of culture in the ‘natural cities’ Christopher Alexander and Jane Jacobs speak of in their famous works are more difficult to plan for, but an ecological understanding can help. These qualities stem from an interconnectedness, dynamic balance and complexity of constituent units that are attributes of rich ecosystems. They are nested in biodiversity and life itself. The way we cohabit with and build life into our settlements will be crucial to the recovery of our nature network. We can design and build places for all life, not just humans, but in which humans will thrive. When we do, the positive effects will pervade an even more green and even more pleasant land.

An ecological understanding

A city is not an island, but we can learn a lot from the theory of island biogeography. A staple reading in my undergraduate biology days, it explains that easy-to-reach islands will be colonised by many species, while isolated ones will be colonised by few. Isolated islands will tend to contain descendants of only a few original settlers: if something happens to one of these species, they can’t be easily replenished from neighbouring islands. As a consequence, they have lower ‘species richness’ (a measure of biodiversity) and resilience to disaster than easy-to-reach connected ones. The area of an island is also important: since larger islands will have more niches for species to occupy, they tend to have higher species richness. This applies to habitats across cities and landscapes that are constricted and isolated by roads, buildings and a plethora of other human hallmarks. While they help connect us, they can be lethal to wildlife and inhibit their long-term survival – one reason why the government should not build more roads post-lockdown.

With this understanding, and by holding a long-term biological time perspective, it is easy to see how local urban design can have an impact on biodiversity and nature networks. Increasing the area of habitat ‘islands’ and connecting them with corridors is the most effective strategy to maintain high levels of biodiversity in cities and beyond. However, as Menno Schilthuizen points out in his excellent book Darwin Comes to Town, the inevitable isolation of habitats in cities can be occasionally “splendid” for evolution and speciation. In places where species are evolving unique adaptations, some isolation could be more suitable. A nature recovery network isn’t so simple as just connecting everything with green infrastructure: as I keep saying, an ecological understanding is very important.

Opportunities for nature’s recovery

Wildness, habitat provision and connectivity are fairly universal across scales for nature’s recovery, but villages, towns and cities carry very different challenges and opportunities. In villages and rural areas where rewilding has the most obvious impact, community can be lacking due to the lack of young people and opportunities for them. This is sensitively displayed in the BBC’s hilarious comedy ‘This Country’, but unfortunately it’s a real problem. A nature-based economy borne from rewilding and a green new deal could go some way to remediating this, creating jobs and community through sustainable energy, regenerative agriculture, tourism and education. Post-pandemic staycation tourism is a topical opportunity for rural areas, and the transformation of county farms and smallholdings in villages have potential for community food growing.

Revitalised farmland, wetlands, woodlands and wildlife corridors would certainly give immense pride of place at the very least, something which is sought in the exciting Natural Assets North project that seeks to build a plan for nature by emboldening partnerships between businesses, national bodies, communities and businesses. These sorts of partnerships are strongly advocated by Natural England and could bridge villages, towns and cities in bioregions. Green belts on the edge of cities hold huge potential as wildlife habitats, natural capital, recreation and community food growing projects. Cities themselves can benefit hugely from the integration of developments into “green grids” of wildlife infrastructure across parks, gardens, streets and rooftops.

We can also be wary of the opportunities brought by technological advancement: directly, through innovations such as the Internet of Things (IoT), or indirectly, through the way technology such as street lighting influences behavioural ecology and evolution. Nature Smart Cities is an example of how IoT can be used for ecological surveying in Stratford, and it will be interesting to explore how cities can become ‘responsive’ to animal behaviour, biodiversity and changing seasons. Further opportunities will arise as our transportation system changes and electric vehicles take precedence. The lack of engine noise alone could have profound effects as we can more clearly hear birds sing (and they can more clearly hear each other). There are innumerable opportunities for rewilding cities, not to mention the reclaiming of streets for cyclists that has taken place throughout the pandemic. Could something similar be sought for nature?

The recovery of our nature network will operate across scales, partnerships, policies and design. We don’t yet know what it will look like but, as urbanists, we have the opportunity to shape part of it. This summer, I will be focussing my Major Research Project on the spatial opportunities for nature recovery networks in rural areas. I’m excited to get going. Although I think I got a bit carried away with this blog…


What can you do?

- Educate yourself!

- Discuss!

- Share!

- Think long-term (on a biological and evolutionary timescale)

- Explore opportunities for nature’s recovery in your work

- Rewild yourself (try not to compartmentalise and fight tidiness)

Recommended sources

Now is the time to educate yourself. I have collated a few resources that might help you on your way:



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