One of my idle pastimes these days has been finding cracks. Once you know how to recognize them, you can see them everywhere. They take a lot of different forms: A man hoeing back the crabgrass creeping across a sidewalk on my way home from work. A scissorlift parked incongruously inside Saint Peter’s Cathedral in the Vatican. The news that the programming language Unix has been vulnerable for twenty-five years, from the core up, to injection attacks of far-reaching capability.

The cities we live in, the roads we travel on, the grids we connect to—all of them, if you inspect them a little, are beautifully rickety things. Please: come with me for a moment on a trip to the forest. First let’s spend the whole day walking through the trees, heedless of where the trails are, just wandering from blueberry patch to blueberry patch, stumbling upon the occasional saskatoons or bunchberries, getting ourselves good and lost. Look, we’ve ended up next to a lake, on a little flat patch carpeted with moss and sedge. It’s getting pretty late. I know more or less how to get us home, but it’ll have to be tomorrow. I can see you’re not particularly worried either; this will be a nice night of rough camping, especially once the mosquitoes die down after dusk.

Did you bring a sleeping bag? Neither did I. Well, let’s build some sort of shelter; it’s going to chill down tonight. There’s a wonderful downed tree right here. Could you go gather up a bundle of good-sized sticks, while I dig up some sand and dirt to bank them with? Excellent, those will do perfectly. I’ve never done this, but it’s pretty simple: we just make a big row of these sticks leaning up on the log, until they add up to a roof. Lean more sticks against the windward opening, and then we’ll chink in the gaps with some dirt. See, it’s looking cozy already. This couldn’t have taken us much more than half an hour. I think this’ll make a fine place to sleep. When we leave tomorrow morning, I don’t think we’ll even need to bother with scattering the sticks back where we found them. Next time a strong wind comes through it’ll do that for us, and until then maybe a fox can enjoy this little spot out of the rain.

Now come with me back to the city. We are in a different world. See this street? This street has clearly been here forever. It is made of stone: you can tell that it grew out of the primordial Earth itself. See those power lines? Like water flowing downhill! They reach inevitably back to their source, and the electricity in them will hum on forevermore. As bears live in the forests, so do humans live in the city, and the city sprouts organically and effortlessly from the accumulation of enough people—and once a part of it reaches maturity, it can stay where it is for millennia, solid as the day it arose. When you compare the city to the country, surely it’s the archetypical example of two different kinds of reality. In one place you’re surrounded by the forces of nature, and in the other you’re surrounded by the constructs of humanity.

Well, it sure can feel that way, can’t it? But really, all the world’s skyscrapers exist in the same world as our little lean-to: the world of freeze and thaw, percolating groundwater, wedging roots, strong winds, and unintended consequences. It takes a conscious effort to look at the Empire State Building, the people going in and out of it every day, the terabytes of data coming and going on its fiber-optic cables, and imagine that someday it might sit unused, and crumble, and become a large pile of stones on an island as green as Manahatta once was. But of course the residents of El Mirador would likely have had just as much trouble conceiving that the city’s great temple would eventually be a funny-looking tree-covered heap of stones at a practically unknown archaeological site in the Guatemalan jungle, reachable only by mule train.

In a human system, everything seems to be carefully placed according to a well-thought-out plan. But the thing is, human systems aren’t alive, and that means that as soon as they’re created, they start decaying. Picture a city: houses, roads, water mains, power lines. Now imagine that each human artifact is surrounded by a bubble of “plannedness”—this bubble is inflated during the construction process, and as soon as construction is over, the bubble starts slowly but steadily leaking. Foundations crack, potholes develop, roots burrow into pipes, concrete softens. And into the little spaces between the shrinking bubbles creeps nature.

Up to a modest scale, it’s not too hard to keep a bubble inflated. Every time you mow your lawn, you blow up the bubble that surrounds it. You can spackle your own walls and plumb out the blockages in your own pipes, and all the other little things that make up day-to-day housework. That’s just a part of being human, from us all the way to the most industry-free tribes of hunter-gatherers. The complications start to arise when your entire environment is built of bubble layered upon bubble layered upon bubble—and your life depends on nearly all of them.

To clean a room requires you and a little free time. To fix a roof requires you, one or two people who live with you, and some hand tools. To tidy up a city park requires a neighborhood gathering, including lots of time dedicated to planning and organizing and getting garbage bags. To fix practically anything larger than that—say, a potholed thoroughfare or a dilapidated stadium—requires lots of people whose sole profession is to reinflate bubbles, as well as truckloads of asphalt, mortar, scaffolding, and fill dirt—and sometimes it isn’t even possible and you just have to start fresh, or give up and leave a hole.

Which is all well and good, so long as you have plenty of people and supplies to go around. But all those people and things have to come from somewhere, and for a long time that somewhere has been oil wells. Maintenance workers did not emerge bodily from oil wells, but their salary did. The things we build with are created using oil power, and sometimes (like with plastic) made directly from oil. And oil is suddenly getting harder and harder to come by. The effect is that we’ve started a long experiment to figure out exactly how small we can let bubbles get before they pop, and how many bubbles can pop before we get back to where we can keep them all inflated.

And those shrinking and popping bubbles, if you can remember all the way back to the beginning of this, are the cracks I keep an eye out for. Some of them are easy to notice. Seems that bridge collapses are becoming a thing. Internet outages strike nearly everyone, even in a country that both leads the world in GDP and invented the damn internet. The interstates that cut through the cores of Minneapolis and St Paul—built there only a few decades ago for tremendous sums of money and the expense of several demolished neighborhoods—are assaulted so vigorously by freeze-thaw cycles that, anymore, they’re only usable for half the year or so, and during the other half they’re in constant repair, closed or down to half capacity. (And people wonder why I bike. Bike trails last a lot longer with so much less weight constantly hammering on them.)

Other cracks are a little more subtle. Computer bugs, for instance. The code itself doesn’t wither away, but the buildup of layers and layers of other code on top of it makes the whole system more and more fragile. Most websites could be taken down temporarily by one or two strategically placed semicolons, and without enough backups, problems could be crippling. Data centers, meanwhile, have some of the fastest-deflating bubbles in the world, requiring daily truckloads of new hard drives (made at great expense and precision) to replace the ones that routinely burn out in the course of normal operation. Next time your computer freezes up or borks out, tally up a crack. Outside of computers, I notice things like flooding low spots, closed-down gas stations in the middle of nowhere, malfunctioning air conditioners, scaffolding in front of famous buildings, overgrowth along highways, broken-down cars, and abandoned buildings far enough away from public eyes that they’re allowed to gracefully crumble and become filled with plants, first on the roof, then progressing down to the bottom level as floors collapse.

The feeling I get from these cracks is hard to describe. On one level, of course, each one means that the skills I (and all my friends) were raised with, all tuned for a civilized context with paying jobs and reliable infrastructure, are one bit closer to useless, and we’re one bit closer to finding ourselves in a spot where we have to learn a lot, quickly, in order to stay alive. But in other ways, each crack feels like a little victory for my team, which is team nature. Each crack is an illustration of what the word “unsustainable” really means, and what happens when you ignore it. Each crack is one step closer to the world I want to live in, and even though I know the steps are far too tiny to get the world all the way there in my lifetime, I like to watch the progression. It’s why I climb those abandoned buildings, and it’s why I point and laugh as I take the bike bridge over a big traffic jam. I like to see overgrown lots and weeds coming up through the sidewalk cracks. It’s a slow conflict between life, which is self-renewing, and constructs, which need constant help—and even though the outcome is already guaranteed, it’s still nice to see that life is winning.