Now, I will not give you an in-depth overview of the big and booming bandwagon of green urban design and architecture. There is already an entire library about this, and I could refer you to the excellent Making Urban Nature (2017), and Designing for Biodiversity (2013). Or the classic Planting Green Roofs and Living Walls of 2004. Or, you could attend one of the many international conferences where architects and planners congregate to discuss the latest developments in ecological urbanism. But what you won’t read in those books or hear in those presentations is how all these new trends in green roofing, nature-inclusive building, and green urbanism affect the ongoing evolution of urban ecosystems. By and large, urban ecologists, ecological architects, and green planners assume that the animals and plants that they release in the urban environment are static—that the roles they play in the network of city life will remain unchanged. As we’ve seen in this book, this may be a miscalculation. There is always urban evolution, and the question is: what’s the cross-talk between urban evolution and urban architecture?
First of all, there’s the telecoupling that we talked about in the previous chapter. Urban engineers, designers, and architects engage in intensive global exchange of ideas. The Argentinian architect Emilio Ambasz creates buildings in Japan, and the Italian Stefano Boeri does the same in China, while Malaysian Ken Yeang works on projects in London, Hong Kong, and Bangalore. All this mobility of people and concepts ensures quick global spread of insights and innovations, and this adds to that telecoupled global urban environment of which we spoke.
But there is more. With a little evolutionary reasoning, it may be possible to come up with a few guidelines on how urban design may harness the power of evolution to assist in the evolutionary maturation of those urban ecosystems. So, here come my off-the-cuff Guidelines for Building with Darwin: four rules for evolutionarily informed urban nature planning.
Number 1: Let it grow. We humans are incorrigible gardeners. We want to plant, to weed, and to arrange. And green urban design is no different. All the greening projects that I mentioned at the start of this chapter, whether vertical, horizontal, slanted or underground, are meticulously planned—not just in looks and function, but also in terms of what shall grow there. The Fukuoka Prefectural Hall roof garden was seeded with seventy-six species of herbs, bushes, and trees. The Lowline Lab in New York used more than a hundred, and Milan’s Bosco Verticale boasts fifty different, carefully selected types of plant. In each of these projects, a team of horticulturalists and arborists would have concocted the ideal mixture of species to suit the specific environment. They would have combined properties such as heat, shade, and drought tolerance with aesthetic characteristics of the forms and colors of leaves, stems, branches, and flowers.
While the hand-picking of such elite troops is understandable, it totally ignores the motley crews of urban plants that these new green spaces are parachuted into. Everywhere in the city, in gutters, roadsides and on non-designed rooftops, communities of plants are co-evolving with each other, with the micro-organisms in the soil and the air, with the insects and other invertebrates that eat and pollinate them, and with the urban environment (the heat island, the patchiness of the soil, the heavy metal pollution, and so on). These evolutionary processes are not helped by dropping a foreign body of pre-assembled plant species among them. Much better would it be to let the green spaces assemble naturally from species growing abundantly elsewhere in the city. This would entail not planting anything, perhaps not even adding soil, but simply leaving the beds empty and letting the urban ecosystem colonize it under its own steam. On a (very) small scale, there are already initiatives that adopt such a “let it grow” philosophy. The Dutch company Gewildgroei (an untranslatable pun meaning something like, Desirable Growth) designs and distributes pavement tiles that contain gaps and holes for soil to collect and plants to sprout spontaneously. On the large scale of an entire building, however, such a laissez-faire approach would mean that that glitzy new “green” project would look terribly bare for the years leading up to the eventual autonomous greening.
Number 2: Not Necessarily Native. If we cannot bear the sight of a naked “green” building, and we really must inoculate it with trees, bushes, and herbs, then why not choose from the local urban portfolio? Any green architecture project will find itself in a city that is already full of urban plants, evolving and adapting to that particular urban environment—ideal starting material! Explore vacant lots, rooftops, and railway embankments and select from the plant species that are already thriving there. “But wait,” the ecological architect would object, “many of those species would be exotic—wouldn’t that go against the urban greening creed to use only native species?” Well, yes, it would; and I maintain that such a creed would be misguided. Of course, it sounds cozy to plant native flora in the city, but we have to face the fact that many of the species that have been evolving and adapting to the urban environment most successfully are non-native—we have come across quite a few examples in this book. It is those ecological supertramps, those citizens of the world that will make up the bulk of that globalized urban ecosystem, and urban planners could do worse than yield to that inconvenient truth of urban evolution.
Number 3: Pristine Pockets. To preserve pockets of original, non-urban habitat inside the city perimeter may seem to go against what I suggested just now in Not Necessarily Native. Still, to keep the engine of urban evolution running, it is important to have a large reservoir of species and genes handy for ecological innovation. The evolving urban ecosystem will regularly be faced with new challenges, and not all the species of the urban food web will be up to the task of adapting to the next urban novelty. That’s why pockets of natural vegetation, which still retain the original, local flora and fauna, can act as a safety valve. Places like the Hassamu nature reserve in Japan’s Sapporo, the Campus do Pici forest in the Brazilian city of Fortaleza, and Bukit Timah in Singapore are such remnants of original old growth forest woven into the fabric of a metropolis.
Number 4: Splendid Isolation. One of the central tenets in urban green design these days is “corridors.” Creating linear strips of vegetation (“greenways”) between parks and other fragments of vegetation in the city to make an interconnected network of urban green spaces is all the rage. It seems like a good idea. After all, it is the urban equivalent of what has been standard practice in nature conservation outside of the city for many decades. When a species disappears from one fragment, it could recolonize from another. This way, the food webs in all those networked reserves stay intact.
Whether corridors are always a good thing in the evolving urban ecosystem is another matter. Think of those white-footed mice from New York, each clan adapted to the specific demands of the park that it found itself isolated in. To them, it may actually be a good thing to be trapped in their own park and not be blended all the time with poorly adapted mice from other parks. The same may be true for many other smaller animals and plants that are trapped in the smallest of urban pocket parks. Like those mice, they probably evolve to adapt to the idiosyncrasies of their particular corner of the city. Connecting those corners via corridors will link those populations and break down those delicate adaptations. So, for the evolution of much of urban life, it might be wise to think twice before planning a corridor.
As you will have noticed, some of these guiding principles go against the grain of ecological urban planning dogma, and it may take a while before city councils internalize a sense of urban evolution. If one has spent decades combating exotic species in one’s city, it will be hard to own up to the fact that one’s efforts are only delaying the inevitable process of evolutionary integration of those species. Similarly, the notion that some urban evolution may be more successful in small, isolated pockets of vegetation than if you connect those pockets with green corridors could be hard to swallow.
So, perhaps we should not count only on the authorities to take a lead in evolutionarily enlightened urban ecosystem management. Communities
of concerned urbanites form perhaps a more powerful vehicle to make a change, and in many countries, city dwellers are already grouping around a shared interest in their local nature. Tokyo is a case in point. As the city grew from one million people in the late seventeenth century to today’s urban conglomeration of 38 million (the Japanese capital is still in the world’s top three, after Guangzhuo and Chongqing), its outskirts swallowed up the surrounding satoyama countryside. Satoyama, as is explained to me by urban ecologists Tetsuro Hosaka and Shinya Numata of Tokyo Metropolitan University, is a catch-all phrase that encompasses the way rural people in Japan have traditionally been managing their natural environment, integrating it in the patchwork of villages, agricultural fields, irrigation channels, and coppice woods.
But, says Hosaka, while those landscapes may be gone, people’s desire to work together toward their common—green—good is still there. Over recent decades, this has led to a reincarnation of the satoyama concept: city dwellers get together and jointly restore and preserve satoyama landscapes on the city’s fringe. There are even some initiatives to apply the satoyama concept to the city center, with groups of neighbors managing the parks, canals, ponds, and roadsides in their quarter, just like their ancestors did in pre-urban times. Moreover, urban farming also becomes a part of this city satoyama, particularly among the sizeable sixty-plus demographic. Numata: “Some old guys are very enthusiastic because they like gardening and vegetable plots. There are so many retired but still powerful and resourceful people. In today’s Japan, sixty-year-olds are still very young and full of energy.” Indeed, on my train journey toward Tokyo Metropolitan University, I see plenty of evidence of this. Everywhere, little orchards and vegetable gardens, even miniature rice paddies are tucked away among the gray apartment blocks. Even in the heart of the city, the affluent residents of glitzy Roppongi Hills come together to plant, tend, and harvest their rice on that roof of the Keyakizaka building.
And Japan’s urban satoyama revival does not stand on its own. All over the world, from Amsterdam to Acapulco, and Zamboanga to Zhengzhou, local urban communities are taking up neighborhood nature conservation and urban farming. The importance of the farming component should not be underestimated, because it means that humans become an integral part of the urban food web. Through their farmed fruit and vegetables, urban humans and their digestive systems are taken up in the energy flows of the local ecosystem. And, since it concerns their stomachs and their well-being, they will automatically become more concerned about that ecosystem.
Perhaps, such groups of ecologically minded city dwellers (which partly overlap with those urban naturalists we came across at the beginning of this book) could prove to be a fertile ground for the notion of urban evolution. In fact, many of the scientists I interviewed for this book told me that city folk are thrilled when they hear that urban flora and fauna are actually evolving to suit the city environment. Think of the potential of involving citizens into urban evolution research!
And that brings me to the final point I would like to make: Let’s build ourselves an Urban EvoScope!
Urban evolution is everywhere. All the animals and plants in our cities are rapidly changing and adapting to those cities. But, with the exception of the handful of urban evolutionary biologists that have marched across these pages, nobody is watching this. There simply aren’t enough scientists to constantly monitor the changing chuckwallas of Phoenix, the evolving eagles of Vancouver, or the adapting adzuki of Shanghai. But, with a global urban population of 4 billion people, there might just be enough citizen scientists to do the job. What if some of those urban citizen scientists, instead of simply recording the presence or absence of species, would also record their evolution?
To give you an example of what I have in mind: in the Netherlands, we recently launched a smartphone app called SnailSnap. With it, people can upload photos of the grove snail (Cepaea nemoralis), common in all Dutch cities, to a central database. The shells of these snails come in many different colors, and our team uses the thousands of photos to figure out whether the shells in the city center are evolving toward lighter coloration. The idea being that snails in a bright shell sitting in the mid-summer urban heat island may overheat just a little less quickly (and therefore survive a bit better) than snails with a dark shell.
Another example comes from acoustic ecology. You’ll recall the changing sounds of birds, insects, and frogs that try to communicate in the urban noise. There are several projects around the world in which volunteers place very small USB-microphones in their gardens or on their homes’ outside walls that automatically, and continuously, record the local “soundscape.” In some cases, like the network of detectors installed in London, this even includes the ultrasonic bandwidth, to monitor bats’ sounds. This way, acoustic ecologists can monitor how animals’ calls, songs, and stridulations change as a result of the racket we humans create.
Then there are some fun ongoing projects that could also be used to keep track of changes. For example, the so-called Funky Nest Contest, run by the Cornell University Laboratory of Ornithology, gets people to send in pictures of the funniest, most adorable, inconvenient, bizarre … well, the funkiest birds’ nests they find in their urban environment. This sort of project could reveal changing (maybe, evolving?) nesting behavior. Do urban blackbirds indeed nest more in and on artificial places than you’d expect by chance? What’s up with those white plastic strips that urban black kites in Spain have started decorating their nests with? Do other birds perhaps also line their nests with cigarette butts like house finches in Mexico do?
These are just a few existing ideas, but think of the possibilities when technologies improve. In the not too distant future, when DNA analysis devices become small and cheap enough, citizen scientists could be monitoring the actual changes in the genes of the urban animals and plants. With improved image recognition software, the photos uploaded to citizen science websites could be used for tracking changes in insect coloration, seed shape, leg length, and all those other ways in which urban flora and fauna are evolving. Together, these monitoring schemes could become a global, permanent EvoScope that keeps tabs on the fluid Darwinian motions that every city ecosystem goes through.
OUTSKIRT
Okay, this hurts. For years, I had avoided coming here. But today, after visiting my mother who still lives in the same 1950s house where I grew up, I decided it was time to take a walk through the new suburbs that have sprung up in the place of the fields and swamps on the edge of Rotterdam, where, as a teenage boy, I laid the foundation of a lifetime of nature study.
It is literally gut-wrenching. I walk among rows and rows of semi-detached houses of the kind that Dutch town planners have churned out by the millions. They are pleasant enough: child-friendly neighborhoods with cute gardens, carports, winding streets with speed bumps, cozy-sounding street names. But to me they are a mausoleum for my old stomping grounds. It is only with the aid of Google Earth that I can work out where, in my outdated mental map, I am.
The neighborhood of De Akkers (a prefab garden shed, an affordable car, and an Ikea umbrella in every front yard) is where I was enveloped in a flock of hundreds of common snipe (Gallinago gallinago), circling the morass while making their sneezing noises in unison—a memory that has stayed with me ever since. Where the De Velden apartment building now stands, I lay in the tall grass with my cheap telephoto to take pictures of nesting black-tailed godwits (Limosa limosa). Now, ring-necked parakeets dangle from strings of peanuts at a bird feeder. And the soil underneath De Gaarden bus station is roughly where I caught the subterranean beetle Choleva agilis in the burrow of a common vole—the pinned specimen now sits in the collection of Naturalis, the natural history museum where I work.
The semi-natural landscape of bogs and pasture where I roamed no longer exists. It has been subsumed into the sprawl of Rotterdam and converted into the kind of urban environment that I have waxed lyrical about in this book. And yet, the confrontation with the starkness of
this process of conversion makes me sad. Is that inconsistent of me? No—of course we must regret what we lose, but that does not mean that what we gain is worthless.
The landscape of my youth instilled sadness in my grandfather, who grew up in the same area at the start of the twentieth century, in a time before pesticides and fertilizers, when insects and wildflowers were much more diverse and plentiful than in “my” 1970s. And to the children growing up today in this suburbia, the remaining ditches, grassy strips, and hedgerows in between the buildings will form the backdrop for their childhood memories, which will be just as precious to them as mine are to me. In other words, as our human footprint gets bigger, the natural world that surrounds us shrinks, changes and becomes poorer. But, biologically impoverished as they may be, these urban ecosystems are still exactly that: ecosystems, with real organisms, suspended in real food webs where real ecology and real evolution go on.
Natural selection here is so strong that urban life forms evolve rapidly. But we must also remember that all the examples of urban evolution in this book form a biased sample of those life forms that were pre-adapted, variable, or simply lucky enough to evolve and survive. For each successful urban species there are dozens of other species that could not adapt to city life and disappeared. Besides being evolutionary powerhouses, cities are also places where great loss of biodiversity takes place. No matter how interesting they are biologically, we cannot rely on them for the preservation of the bulk of the world’s species. For that, we must preserve, appreciate, and explore what remains of pristine, unspoiled wilderness.
Darwin Comes to Town Page 21