CityReads│When Darwin Meets City: How the City Drives Evolution

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When Darwin Meets City: How the Urban Jungle Drives Evolution

Many species are adapting to the contingencies of urban life, creating a fresh wealth of biodiversity.

Menno Schilthuizen, Darwin Comes to Town: How the Urban Jungle Drives Evolution,Picador,2018

Sources: https://us.macmillan.com/books/9781250127822

http://blogs.sciencemag.org/books/2018/04/10/darwin-comes-to-town/

https://www.nyjournalofbooks.com/book-review/darwin-comes

With human populations growing, we’re having an increasing impact on global ecosystems, and nowhere do these impacts overlap as much as they do in cities. The urban environment is about as extreme as it gets, and the wild animals and plants that live side-by-side with us need to adapt to a whole suite of challenging conditions: they must manage in the city’s hotter climate (the “urban heat island”); they need to be able to live either in the semidesert of the tall, rocky, and cavernous structures we call buildings or in the pocket-like oases of city parks (which pose their own dangers, including smog and free-ranging dogs and cats); traffic causes continuous noise, a mist of fine dust particles, and barriers to movement for any animal that cannot fly or burrow; food sources are mainly human-derived. And yet, amid our skyscrapers and cracked sidewalks we can observe nature’s resiliency as it responds to the brutal domination of a single “cornerstone” species, Homo sapiens sapiens. as Schilthuizen shows, the wildlife sharing these spaces with us is not just surviving, but evolving ways of thriving.

Menno Schilthuizen is one of a growing number of “urban ecologists” studying how our manmade environments are accelerating and changing the evolution of the animals and plants around us. In Darwin Comes to Town, he takes us around the world for an up-close look at just how stunningly flexible and swift-moving natural selection can be. Darwin Comes to Town draws on eye-popping examples of adaptation to share a stunning vision of urban evolution in which humans and wildlife co-exist in a unique harmony. It reveals that evolution can happen far more rapidly than Darwin dreamed.

Far from viewing large cities—London, New York, Tokyo, Singapore—as the enemies of nature, Schilthuizen advances the idea that many species are adapting to the contingencies of urban life, creating a fresh wealth of biodiversity.

Metal-excreting pigeons, pigeon-eating catfish, cigarette-wielding sparrows, soprano-voiced great tits: The modern city is a fantastical menagerie of the odd and unexpected. Through a series of 20 short but connected chapters that mix natural history vignettes, interviews with visionary scientists, and visits to childhood haunts, science journalist and biology professor Menno Schilthuizen introduces readers to the striking facts of ongoing urban evolution in Darwin Comes to Town.

Two cross-cutting ideas permeate the book. The first is the notion of rampaging sameness. Because we are incessant, but messy, busybodies, Schilthuizen argues, we scatter species across countries and continents. And we move most among cities.

The author conveys this urban sameness through the transformation of Singapore. Of the original 208 square miles of rainforest that clad [Singapore] two centuries ago, when the Sultan of Johor allowed the British to pitch their imperial tents, less than one square mile remains. Now observe a scene along an estuary in Singapore: the house crows and the mynas feeding in the cow grass, the apple snails laying eggs among the mimosa, the red-eared slider turtles dipping into the water, and the peacock bass breaking the surface for a gulp of air. Every one of the species he describes is a non-native, every one is found in countless other cities the world over, and every one is at home in its new habitat. Schilthuizen has even borrowed a name from parasitology for them: anthropophiles. It is those anthropophiles and the niches they carve for themselves in the human-engineered ecosystem that we will discover in this book.

And the reason for this biological sameness is urban sameness. Cities around the world produce the same sorts of garbage and the same sorts of noise, house the same sorts of skyscrapers, and produce the same fragmented landscapes. They can even generate the same sort of weather via particulate pollution and the heat-island effect.

Some research indicates that the ecologies of cities are more similar to each other than to those in nearby rural patches: “What all this means is that the ecosystems of the cities around the world are growing more and more alike; their communities of plants and animals, fungi, single-celled organisms, and viruses are inching toward a single globalized, multi-purpose urban biodiversity . . . In the unspoiled forests, deserts, swamps, and dunes far from human interference, evolutionary change is driven by age-old natural forces . . . in cities . . . it is the other way around.”

The book’s second major theme is that rapid change is an enduring part of the urban environment. Urban plants and animals evolve and adapt to their novel urban surroundings at remarkable speed.

The city pigeons’ darker, more melanic feathers sequester poisonous metals. 

The great tit’s new soprano notes are better heard above the city din.

City moths in Europe have become less attracted to deadly artificial lights.

Carrion crows in the Japanese city of Sendai have learned to use passing traffic to crack nuts.

Lizards in Puerto Rico are evolving feet that better grip surfaces like concrete.

In Britain: the peppered moth, who, during the advent of industrialization in Manchester, swapped its gray mottled wings for black so as to blend in with the soot that blanketed streets and foliage (and to avoid the keen gaze of hawks and other predators).

In Paris: groups of parrots that differ genetically, depending on their neighborhoods.

In New York City: populations of common white-footed mice, cut off from each other in parks such as Manhattan’s Central and Brooklyn’s Prospect, and that reveal genetic adaptations to their environments, especially a toleration for fast-food scraps and pollution.

In Bridgeport, Connecticut: a mummichong (Fundulus heteroclitus), a finger-sized fish who thrives in the PCB-clouded harbor, water so toxic it would kill most other marine life.

And in Albi, a city that straddles the Tarn river in southern France: pigeons flock to the Pont Vieux, bathing and preening along the shoreline, unwitting victims to Silurus Glanis, the continent’s largest freshwater fish. (Some specimens run over six feet long.) These catfish are not native to western Europe and were only introduced to the Tarn by anglers in 1983. In 35 years they’ve evolved an unusual predatory behavior: they will beach themselves to nab unsuspecting pigeons, drag them underwater, and swallow them whole.

Indeed, the realization that adaptive evolutionary change occurring on human time-scales in multicellular species is common, rather than rare, is both fairly new and fairly profound. The ubiquity of the phenomenon has even given rise to a new field known as eco-evolutionary dynamics.

It is now clear that adaptation can be so fast as to affect the very environment that sets the stage for those adaptations, leading to possible merry-go-rounds of organism-environment-organism changes through time. The implications of this are still not fully known, but it’s safe to assume that this is not what Darwin envisioned from his seat in the Kent countryside.

The fact that urban evolution is surprisingly fast also supports one of the radical ideas promulgated at the very end of this book: a vision of a city engineered to encourage the continued adaptive evolution of other species. We could, Schilthuizen argues, become evolution engineers, promoting the evolution of traits that will stand both us and our anthropophiles in good stead, such as using thriving non-native plants to populate green roofs or actively suppressing genetic mixing. As lineages continue to evolve, we can reengineer their environments as needed. A project of engineering urban evolution is likely to pique interest, discussion, and perhaps even directed research. But this is clearly a view of nature that is more Abu Dhabi than Amazon rainforest, more engineering than awe.

As our world grows increasingly urbanized, as we design “green” buildings among our congested downtowns, Schilthuizen’s book makes for essential reading.

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