From backyards to backstreets, evolution marches on.

A towering grey mountain reaches up to the dazzling blue sky, almost as of balanced on its toes. Its sides are sheer, and drop away sharply to the ground, hundreds of feet below.

Embedded in its sides are countless little nooks and crannies, large enough to make a nest or resting spot and a strategic vantage point from where to survey all the goings-on below. Or, with a sweeping spread of wings, perhaps even stage a swooping vertical ambush on passing food.

This is the kind of place where peregrine falcons like to live. Large, open expanses of sky, abundance of pigeons and other prey below, and a high perch from which to observe it all. And this is where they have lived, from time immemorial.

Of course, times are changing. In the days of old, all mountains were tall, rounded and undulating. Today, they’re increasingly becoming sharp and square, but that doesn’t matter much, because height is the distinguishing factor.

And what could be higher than the Empire State Building?

Most people don’t think of cities as part of “nature”. If they want to see nature, they’ll go to the countryside (assuming they don’t tune in to Discovery Channel).

And indeed, the typical city, with concrete sidewalks, tarmacked roads, and perhaps a lone tree standing here and there, isn’t exactly what you would describe as “natural”. This is the human heartland: a place designed by humans, for humans, and fine-tuned to serve human needs perfectly. Nature is kept safely inside parks and zoos, and isn’t allowed to interfere with the rest of the city. There’s no place for both at once.

But do humans always have to be separated from the rest of “nature”? Evidently not.

In Japan, humans and wildlife have coexisted for hundreds of years in what is known as “satoyama”. This is the in-between place where farmland meets forest, and it has been around so long that humans’ paddy-planting cycle has become a part of the ecosystem. When humans divert the stream to flood their fields, in preparation for planting, that’s when catfish come to burrow in the freshly turned soil and lay their eggs in moist plough-valleys. Dragonflies flit above the water, dipping in once in a while to lay their eggs — some of which will fall prey to the catfish, while others survive to set off the cycle once again.

It’s not just a one-way system: humans rely on satoyama too. For example, the ponds offer a much-needed nesting place for ducks during their long winter migrations — some of them leave, refreshed, while a few others form tasty meals for the humans. Frogs, fish, insects; they’ve all come to rely on the annual human activities, just as humans have come to rely on them. So has the paddy, of course.

These days, satoyama is slowly getting swallowed up by expanding cities. Luckily, it isn’t the only kind of place wildlife can adapt to.

A row of white strips crosses the road, going from one side of it to the other. But you can hardly see it for the noisy machines crowding around on top: Honda’s, Suzuki’s, Mazda’s and Subaru’s, in all manner of shapes and colours, all working together to form the great Nutcracker.

The Nutcracker takes some getting used to, but it’s really quite convenient. No more tiring flights high into the air; no more chasing your nut as it plummets to the ground and hoping it cracks first time so you don’t have to start over.

Using the Nutcracker doesn’t require so much corvial labour, though it does call for finesse. You can place your nuts near kerbs, speedbumps, and pretty much anywhere else the coloured machines tend to slow down. The best place, however, is at a zebra crossing. Wait till the lights turn red, bringing all activity to a standstill. Place your nuts along the empty tarmac, and wait for the traffic to resume again.

Next time it stops, just hop in and collect your freshly cracked nuts.

This trick was invented by the crows of Kadan driving school in Sendai, where a maze of traffic-cones and slow-driving cars makes the perfect nut-cracking setup. Now, the tradition has rapidly spread all over the city.

Cities are, generally speaking, not great for biodiversity. Shrubs and trees make way for junction-boxes and lamp-posts; rich topsoil is replaced with expensive concrete, and local grass with imported lawns. Animals and insects have no ecosystem to support them. Those which don’t move on their own are chased off by angry humans. Most species depend on a whole network of other species to help them survive, and that network cannot be maintained by just a few trees growing from under the concrete.

But those species that do manage to stick around, often adapt themselves to city life. Sometimes they like it so much, they don’t want to leave. And those veterans who’ve lived in cities for hundreds of generations, they actually evolve to work with the city. Their genetic makeup adjusts to match, on the road to a possible new species.

While that hasn’t happened yet, one can already see the changes if one looks close enough. Cliff swallows that nest on the highway bridges of Nebraska, USA, have shorter wings than cliff swallows living in open foothills and valleys, because shorter wings are better suited to quickly flying out of oncoming traffic.

When Charles Darwin went to the Galápagos islands, he noticed how finches evolved different beaks on different islands, to make best use of the available food.

In places where seeds were large and tough, finches evolved thick sturdy beaks to crack them open. Meanwhile, small-seeded islands had finches with smaller beaks, all the better to daintily pick up a meal. The cactus finches had a dual-purpose longer beak, allowing it to suck pollen and nectar during the flowering season and seeds the rest of the time; the warbler-finches, on the other hand, had short, pointed beaks for picking up insects — though not so short as the woodpecker finch which (you guessed it) picked insects out of wood.

Today, the dandelion finds itself in an archipelago just like the Galápagos — except the islands are separate by not water but concrete. And like its island-dwelling relatives, the dandelion’s seeding habits are changing to match.

The dandelion has two kinds of seeds: heavy ones that fall right to the ground, and light ones that drift around on the wind exploring for new places to settle. This gives the dandelion the best of both worlds: the heavy seeds will definitely find good soil, since it’s the same one that their parent plant used; and if there are more potential growing places around, one of the light flying explorers is sure to find them.

On an island, things are different. If a seed flies too far, it’ll fall off the island into the empty sea — not a good place to grow at all. That’s why island plants tend to have heavier seeds which don’t fly too far: they can still drift around, but not so much that they stray from the land.

That’s why the dandelion’s island-dwelling relative, the Hypocoeris radicata or “cat’s ear”, has only one kind of seed: the heavy one that falls right to the ground. And now, dandelions trapped on concrete islands have learnt to put out heavier seeds too.

Rural areas tend to have only local species, and they vary widely from place to place. Cities are more cosmopolitan.

Look into any city, whether it’s Toronto or Tokyo, and you’ll probably encounter much the same set of creatures: house mice, silverfish, cockroaches, rats, and, of course, the common pigeon. Planes, ships, trains, cars and trucks are constantly moving between cities — carrying around things like seeds, humans and mice, some of whom stay behind to spread and grow.

The same applies to microorganisms too. Look into an empty hotel bathroom, and you’re likely to find the orange Aureobasidium pullulans fungus, which has spread as people move their toiletries from one bathroom to another. Today, hotels will harbour A. pullulans almost as surely as AirBnB’s will have a café round the corner.

That said, city creatures can be very individualistic. Have you even been bitten by a mosquito? I’m guessing you have, since they’re so common everywhere. But the London Underground has got its own unique species. They don’t hibernate in the winter like others, since the metro tunnels are warmed by humans and engines all year round. Crowded trains also provide a good source of nutrition for young mosquitoes, which mothers-to-be make use of in a neat instance of “human resource development”.

Genetic studies have shown that the Underground has not one but three subspecies of mosquito: one from the Central line, one living in the Bakerloo line, and a third which lives on the line to Victoria.

City life is not for everyone. You have to adapt to the loud background noise, raising your songs to a higher pitch if you want to be heard. You need to learn to navigate and deal with new objects, and be prepared to dodge out of their way very, very fast.

But cities also provide opportunity. If you can make it, there’s a steady supply of nutrition in dustbins, garbage-dumps, and sometimes just kitchen windows. Plants can utilise rare nutrients in the soil, if they manage to separate them from all the toxins.

When a city comes up, it destroys a lot of creatures, and only a few come to take their place. With support systems gone, humans have to rely on machines to keep things going: machines which other animals make use of too, but humans can’t survive without.

Which begs the question: will humans ever adapt to life in the city?

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