by Rob Dunn
Despommier went to Newark unsure what would result. Investors were joining him and the mayor, Corey Booker, the man who wants to put Newark on the map for something other than its smell. Despommier brought pictures of his futuristic plans for vertical gardens. He brought the statistics about the number of people on Earth, dwindling food supplies, and even more dwindling forests. He stood in the front of the room, and he pitched his idea as if our future depended on it. He was now, officially, the one who was dreaming big, who was hoping for the future. The mayor’s people asked cynical questions about one part of the project and then another. The investors asked questions. Then after more discussion, the mayor and Despommier had a private meeting to talk about the future.
In the private meeting with Despommier, the mayor’s people agreed to move forward. They would have a prototype built, a small vertical garden. Let us see, they said in essence, how many people we can really feed. A prototype garden is a tiny germ of what Despommier believes to be possible, but then again one might say the same of an apple relative to its tree. Meanwhile, another garden building is in the works in Italy, and elsewhere conversations are beginning, conversations where individuals give in to the power of what ants lack, the power to dream.
In the meantime, the future of urban life is not hitched exclusively to Despommier’s tractor. Rooftops are being greened whether or not vertical farms are ever built. Rare species are being restored and as this happens, more and more of us can sink our hands into that life. We know some of the reasons we need other species. As time goes on, we will learn others. More remains unknown about our bodies, and so there is much to explore and understand, as there will be for generations. Given the choice of which and how many species to live around (a choice we still have, though not forever), why not consciously garden a greater diversity of life around us, be that life our crops or something even richer? Why not foster the conservation of the interplay between humans and the rest of life, to paraphrase René Dubos, and favor the species from which we benefit, rather than those that haunt our cupboards and the walls of our houses. Why not? We hang bird feeders to favor beautiful animals. Why not design whole cities to favor the species that tend not just to our pleasure, but also to our sustenance and sanity?
The question is which species we might favor, and how. Favoring our food crops, as Despommier has suggested, might be a good start, as would favoring the other species on which they depend, their pollinators, for example. Such species benefit us directly. We eat them and eat of their success. We could have honeybees, bumblebees, hummingbirds, sunbirds, and other curve-beaked nectar-lovers in our cities, but we could also have more.
To answer the question of just which species we could favor, it is worth revisiting our own story, the one that begins with the first life, passes through our potential ancestor Ardi, and leaves off in our homes today. If I retell this story in light of the material we have covered in this book, it goes something like this. Once upon a time, we lived life in nature’s tangled bank. Five hundred million years ago, our hearts evolved to pump blood. Their beating was physiological, but nearly every subsequent elaboration on our bodies related to interacting with the rest of life. Four hundred and ninety million years ago, the first eyes evolved in order to detect prey. Later, the first taste buds evolved in order to help us find our food species and avoid toxic species, to urge us toward what we needed and away from what we did not. Our immune systems evolved to detect microscopic creatures and distinguish among them, favoring some and disfavoring others. All of this we share with most of the rest of animal life. In this way, our bodies unite us.
As we moved closer to becoming human, a few traits became especially accentuated. Our vision improved, whether to detect snakes and other threats or fruits. Our long legs evolved to help us chase prey. Our lungs expanded. Our hands evolved their particular abilities in order to hold weapons. Somewhere among this series of moments, we developed the consciousness that would lead us, several generations down the road, to build cities and societies.
Our consciousness is only partial. We are conscious of the senses that we use to hunt, forage, and be social. We are not conscious of our immune system’s choices, though our immune system acts in ways very similar to our other senses. None of our senses allows us full awareness of what is around us, nor, for that matter, of our decisions. We miss a range of sounds, smells, tastes, and textures obvious to other animals. We also miss most of the signals that our own eyes, noses, ears, and taste buds provide to our brains, signals that carry out on our behalf actions of which we are essentially unaware.
Oblivious to the ways our bodies depend on the species around us, we obeyed our senses. We remade the world to suit our pleasures. We excluded many species from our lives and then intentionally favored a select few, a tiny minority of Earth’s diversity. Meanwhile, a suite of other species—species we now think of as pests—sneaked over our barriers and walls. They arrived, unbeckoned, in our lives. Or at least that seemed like what happened. But I have left one surprise in the story. It turns out that the species that snuck through with us into our modern lives are not a random draw from the possible life-forms on Earth. They are—these sneaky rats, roaches, and bedbugs—nearly all from the same place, though no one had noticed until recently. We had been too busy trying to kill them to pay attention to how they evolved.
In the fall of 1985, Doug Larson was hanging 600 feet above the ground. He and one of his students, Steve Spring, were looking at pine trees growing out of the cliff face, each one clinging tenuously to life. Spring was doing a rather ordinary thesis about trees that grow on rock faces, and Larson was along to mentor. Except for the precariousness of their situation, it was workaday science. The plan was to take samples of the trees to figure out how old they were. It was the student’s idea. Larson would rather have been studying lichens, but he was happy to be exploring and obliging his student for a while. As Larson and his student bounced back and forth from the wall, anything might have happened, and so it was that something did.
Until his moment on the cliff, part of the Niagara Escarpment, Larson had studied lichens for his entire professional life. They were lovely and persistent. They were also irrelevant to most of humanity, or at least they seemed that way. A case can be made for lichens, to be sure. They are a near miraculous fusion of algae and fungi, life-forms that in coming together can live in a way—on rock faces, eating air, sun, and minerals—that neither can on its own. Still, Larson found himself, again and again, having to make the case.
Then came the cliff. On the cliff, Larson and Spring sampled a few of the trees, eastern white cedars (Thuja occidentalis), none wider than Larson’s forearm. The trees were stunted, twisted, gnarled, and otherwise beat up. It was silly, really, to study their age. They were clearly young trees, hanging on for a few years between germination and their eventual fall from the face. Or at least they seemed to be. When Larson and Spring came back to the lab, they were in for a big surprise. They looked at cores from the trees under a microscope and found not the few dozen rings they had expected, but instead hundreds of rings. The trees were hundreds of years old, an ancient forest suspended in midair. In fact, they were among the oldest trees on Earth.5 They had resisted not just gravity, but also, somehow, time.
The consequence of discovering these trees was twofold. The age of the trees was the first piece in what would become an important and much longer story. Ancient forests would prove to reside not just on the cliffs near Larson’s home, but instead on many cliffs, refuges of the past here and there around the world. Trees a thousand years old and older were found on rock faces in Canada, the United States, the United Kingdom, and France. Larson, the once-obscure scientist from Guelph, became one of the better-known Canadian biologists, a voice for interesting old trees. The other consequence though was that in looking at these trees, Larson was spurred into looking at the life on cliffs more generally. As he did, he started to view cliffs as significant, central even, to who we are as huma
ns. A long way from any major city, he even came to develop a new theory about the emergence of our modern urban lives.
Larson’s theory was a coming to terms with the similarities between his one life in an office on a campus and his other life, dangling off ledges. It was also the coming together of minds. He formed the theory along with a group of five other scientists* whose thoughts had begun to converge on his own. Together they discussed the idea excitedly, only to broaden it a little more and then, when modesty struck, rein it in and then broaden it once again. The five, with Larson as lead author, published the theory, in its nascent form, in a book on cliff ecology (the only book on cliff ecology).6 Then, when that did not seem sufficient, they wrote an entire book about the idea, The Urban Cliff Revolution. In the first and most often discussed part of the book, Larson and team argue that the cities we build are like cliffs, populated with cavelike rooms and balconies. We build these clifflike environments even though they are marginal and unproductive, they argue, because through the long years of early human evolution, caves and cliff sides were our refuges from the elements and from predators. We build cities out of cement and up into the sky because they remind us of cliffs and caves. This, however, was not the only radical idea in the book.
In addition to their big idea about our fondness for caves, the team offered an explanation for the origins of the species—whether dandelions or pigeons—that live with us in our cities. They noticed that the species that make it unbeckoned into our cities tend to be the very same species that originally lived with us in caves or on cliffs. In cities all over the world, we have created a vast network of caves and cliffs into which species that evolved to live under such conditions have moved, as content and successful as they have ever been.
Cliffs occupy a tiny proportion of the earth, less than one in ten thousand acres. More land is now devoted to parking lots than to cliffsides and caves. If cliffside environments contributed randomly to city biotas, just one in a thousand of the species we see in cities would come from caves or cliffs. Instead, Larson has found that nearly half of the plant species in his home city grew first along cliffsides. The results for animals were similar. The list of species from cliffsides is a who’s who of the life outside our windows. Dandelions, Norway rats, German cockroaches, bedbugs, plantago, peregrine falcons, rock doves (pigeons), starlings, cliff swallows, house sparrows, barn owls, earthworms (and a lovely, introduced glowworm that feeds on nothing but urban earthworms), and many more of the species that live in our cities evolved in caves and cliffs.* Some species, such as some cave crickets and firebrats, are now more common in our houses than they are in caves. These species not only happen to be the ones we have favored but they have even continued, in many cases, to live as they once lived in caves. Rock doves still nest in crevices. Their ancient predators, peregrine falcons, still stoop on them among cliff faces (albeit glass ones). They still take off “vertically and explosively,” to quote Larson and colleagues, as they must for lack of runway.
This second idea of Larson’s may seem like a modest biological detail, but it is not. Larson’s idea about the origins of urban life-forms suggests how we might manage the life in our cities. We tend to treat life in cities as though it were simply a degraded version of nearby forests. We tend to trees and talk about “urban forestry” so often that it is now considered a field of study unto itself. The truth is, cities are something else, perhaps, as Larson suggests, a landscape that includes forest, but also far more in the way of caves and clifflike walls. If Larson and friends are right, the species we have chosen to live near us are accidentals, consequences in their success of the type of cavelike habitat we happen to have made. Until now the life we appear to have gardened around us—not for food but by accident—is favored by the structure of our lives and surroundings. If right, Larson’s work suggests that we need to rethink how we manage the species that live nearest to us and that we need to do so, in part, by altering the infrastructure that surrounds us. We need to favor not just the species that happen to persist, or tumble-down versions of the forests and grasslands we find farther from our cities and towns, but instead create something wilder and more interesting.
Here I will offer my own vision of what could be. I am, I admit, caught up in the revolutions of Despommier and Larson. Maybe a first course of action is to try to grow as many beneficial or potentially beneficial species as we can in cities, ideally species native to the regions in which the cities are found. They should come from cliffs and canopies (because it turns out that canopy, the dry tops of trees, is the other habitat that resembles cliffs). Imagine green walls of wild species in each and every city, even rare species, among which flit hummingbirds, butterflies, and bees. Imagine the tangled bank of wildlife rising up out of street medians. Imagine too larger green walls of life, interspersed with vertical farms. Some of these species have already made it, as harbingers of what can be done. In Hong Kong, the epiphytes that once grew exclusively on trees now grow on some downtown buildings, in great numbers (if not yet great diversity). In Mexico City, several dozen species of lichens grow on buildings and tree trunks. We could add to these species and bring with them their dependents. We could also plant fruit trees in medians, and berries could cascade off balconies. We might forage within our cities as we walk, as we once all foraged. We might remember how to gather life, both food and well-being, and if, in the process, we also gather a wider diversity of good microbes and a worm or two, so be it.
Right now, our biggest barriers remain our brains and their biases, brains that still tell us that a green pesticide-treated lawn is more healthy than one abounding with species, brains that still tell us the same things they told us when we lived in caves and when mammoths still walked along the horizon. There are logistical impediments too, some small, some big. Pollution will (as critics of Despommier’s plans suggested before they realized his gardens were indoors) make some of the fruits and foods we grow in cities toxic. In Mexico City and elsewhere, it has killed lichens (in fact, lichens are used like a canary in the coal mine, an indicator of such pollution). But surely if our cities, or at least some of our cities, are too ridden with toxins to eat their fruit, the answer is to clean up our cities, not throw out our fruits. We must be able to bite into the apples that grow on street corners. We have given in to the temptations of our origins for most of our history and must now give in to something else, a vision for the future of life. If the first bite is bitter, if our first and current cities are not quite right, we should plant the seed again until what grows from our society is sweet.
If we do not succeed in preserving a rich and useful nature in and around ourselves (as our appendix attempts to do inside our bodies), the rest of nature will run us over. For all the worry about the end of nature, the persistence of life itself seems assured, at least over the next millions of years. Nature lives in hydrothermal vents and clouds. It thrives at temperatures hot enough to boil water and cold enough to freeze the marrow in our bones.
What we should worry about is the end of our nature, the links between humans and other species, links on which our very existence depends. To return to Dubos, “if we [do] not manage to create environments in which human beings, and especially children, could safely express the rich diversity of their genetic endowment,” we will fail. But it is not just that our bodies miss other species and their richness. The secret that runs throughout this book, the one that I hope to have shown more than I have discussed, is that our bodies and lives only make sense in the context of other species. Only by looking at other lives do we really understand our own.
Some of the ways we look to other species to understand ourselves are so ordinary that we forget them. We do experiments on mice, guinea pigs, and rats because they are enough like us that when we understand them, we understand ourselves. But the truth is broader. Much of what we learn about ourselves comes not from lab animals, but from the wild labs of the Amazon, the Serengeti, and other places where species still mate, die
, and flee of their own volition. It is in the wilderness, after all, that we see the evidence of the effects of snakes and predators on primates. It is by looking at other species that we put our appendix in context. It is in termites and other insects that the beneficial roles of microbes in guts first become most clear. It is in the ant societies that we see the most general understanding of the origins of agriculture. It is where the wild things are that we see our bodies and lives most clearly. We make sense, you and I, only in the light of our understanding of the general rules and tendencies of ecology and evolution.
How much is the understanding that we garner from the wildest places worth to us? It is hard to say precisely, but what I can say is that when we lose wild monkey species and their predators or even snakes and rare ants, we lose the most reflective mirrors with which we are able to examine ourselves. We need to maintain the kinds of wild places in which the truths about who we are are most evident. If that means rewilding the Great Plains with cheetahs so as to be able to see pronghorn once again running for a reason, so be it. Let their flight remind us that our lives, whether we notice or not, are still and will always be where the wild things are.
Acknowledgments
As humans, we tend to look straight ahead. It is a legacy of our heritage as gatherers and hunters. Looking to the periphery at our context or even looking back to where we have come from is more difficult. The view is never totally clear. Fortunately, I have been helped tremendously in my attempt to look at our context, both ecological and evolutionary, by the perspectives of others. Many individuals have helped me to see.
