What Would Happen If Every Human Vanished? | Astrum Earth

0:00Humans have taken over the world. Almost everywhere you look, we're surrounded by our own existence. Everyday objects, buildings, cars, even intangible things like language, music and the stock market. It's impossible not to notice us. But I've always wondered what would happen if we were removed from that equation. Well, luckily for you, that's what we're about to find out. As we wipe all 8.3 billion humans off the face of the earth in a flash, gone. Not lost to an aggressive global pandemic or obliterated by an incoming asteroid. This is what would happen if we just vanished. But even then, we'd still leave a lot behind. Reminders of the civilizations that once stood. As nature reclaims the planet, the question then becomes, would any clues of our existence remain? Or would it be as if we never existed at all?

1:00I'm James Schuert and you're watching Astrum Earth. Join me in this video as we dare to imagine our planet without the most dominant species that's ever lived on its surface. How long would our world survive without us? Would nature begin to reclaim all it had lost? Would any trace of humanity even remain after a thousand years and a million years? Or would Earth eventually raise us completely as though we'd never existed at all? And the thing that I'm most interested in is which species would take over in our place. And that, I promise, is going to shock you. Before you become overwhelmed with the philosophical dreads at the thought of the human race disappearing completely. Remember, this is just a thought experiment. I'm not going to freak you out by imagining how we may have met our grizzly ends. So let's pretend we've just vanished into thin air and leave it at that, leaving no biological remains behind.

2:00In that, albeit in probable case, what would happen in the hours, days, weeks, months, and years after we've disappeared? It's quite likely that the immediate moments after our departure would be... How can I put this? Pure chaos. Within 24 to 48 hours, blackouts would start happening across the globe, with no one left to provide the fuel needed for power stations to function. Renewable energy sources like solar and wind turbines might be able to keep some power going on for a while, but without a proper maintenance of the world's electricity distribution networks, these two would eventually cut out. Anyway, what about nuclear power? Well, these reactors are already designed with backup protocols in the event of a natural disaster or power outage. So these would probably kick in soon after humans disappeared. They do come with a kill switch called a scram, which can shut the reactor down completely, but with no humans to maintain them,

3:02their cooling water would soon start to evaporate. And it's only once this happens that things get pretty bad. Reactors could be sent into meltdown. Unlikely release large amounts of radiation into the surroundings. There are currently around 440 nuclear reactors operating in 31 countries around the world, so that's a lot of radiation. And it does beg the question, what would this do to Earth? Well, we don't necessarily need to wait to see what we don't fold in this scenario, because we've already experienced two major reactor accidents during our time on Earth. Chernobyl in 1986 and Fukushima in 2011. Chernobyl is perhaps the more famous, a total meltdown of the nuclear reactor core, releasing substantial amounts of radiation into the environment. The nearby town of Pripyat was evacuated as a result of this contamination, and something amazing has happened. It's become a biodiversity hotspot,

4:04despite its resident animals experiencing years of chronic radiation exposure. In fact, a study published in 2015 looked at wildlife populations in the Chernobyl exclusion zone, and found no evidence that the radiation had long term negative influence on mammal abundance. Actually quite the opposite. The number of elk, red deer and wild boar within the exclusion zone rivaled those of uncontaminated nature reserves in the region. There were more than seven times as many wolves than found in those other reserves. Chernobyl shows us that when faced with an environment deemed too dangerous for permanent settlement by humans, nature not only endures but thrives. It's therefore likely that if there were any nuclear disasters caused by our disappearance, nature could recover faster than we may expect within a century even. And if it can take over radioactive ruins in that time, then what charts does the rest of our infrastructure stand?

5:05Nowadays more than half of the world's population lives in cities. They're a unique product of the human experience, tailored for our busy lifestyles and cultural quirks. So what happens to them when you take away the very reason for their existence? Us. In all the talk of a world without humans, there's a rather lovely irony in welcoming a new one to the world, which is exactly what's happening in my house pretty soon. Before our new arrival, I wanted to make sure I was as healthy as I could be to be the best dad I could be. But also, I have a feeling I might need a bit of energy support pretty soon, not a sleepless nights coming my way. So I've been drinking AG1. Just like you, we have a pretty hectic life here. So drinking something that's clinically shown to fill common nutrient gaps and contains 75-plus ingredients, designed to support things like gut health, daily energy and my immune system, or without turning my morning routine into a 17-step wellness ceremony,

6:06is a total game changer. I drink mine with my breakfast, and all I have to do is just mix one scoop of AG1 with around 250ml of cold water, shake it up, and drink. That's it. I'm pretty fussing when it comes to flavours. This actually tastes really good. Kind of like pineapple and vanilla. Trust me, it doesn't feel like a chore, you know how some drinks do. It's been a couple of weeks now, and as someone that doesn't drink caffeine, the energy support is so noticeable, especially in the afternoons, when I used to flag a little bit around 3-4 o'clock. So why not do something for you and invest in your health as well? Another great deal for you right now with 20% off your first subscription order of AG1 next gen or AG1 Pro. Just head to drinkag1.com slash AstrumEarth or scan the QR code on the screen right here. Thanks to AG1 for sponsoring today's video, and now we head back to the actual chaos.

7:09As it turns out, at least one human was thinking about this question before we all disappeared. Alan Weisman is an American author and journalist who wrote a handy book on this topic called The World Without Us. Now in an interview about this book, Weisman used New York City as an example to describe the post-human era. And funny enough, he believes a post-human New York would look very much like the pre-human New York. To give some context, the Lennarpay people who have been living in parts of the Big Apple and surrounding areas for around 3,000 years called the island Manahata, meaning island of many hills. And by the way, you may not think of New York as being a particularly hilly area, but that's because we Europeans got there and evened it out. Anyway, British explorer Henry Hudson was one of the first Europeans to write about Manhattan back in 1609 and described a forested land very abundant in all kinds of timber, suitable for shipbuilding and for making large casks.

8:12The Dutch-Drogopher Johans de Lat also wrote about the island, saying that the land is full of noble forest trees and grapefines. From these accounts, it's clear that New York was once a rich forested landscape with rough terrain and abundant wildlife. So if humans were to disappear, this is probably how it would look again. The question is, how? It might not be immediately obvious, but cities battle large volumes of groundwater running through their drainage systems every day. And it requires Herculean human effort to stop it from infiltrating systems like the underground or the subway. Even on a sunny day with no rain, New York subway maintenance workers pump nearly 50 million litres of water away. So if all those people were to suddenly disappear and the power cut out, it'd be a matter of days before rivers surged through these tunnels and plunged the subway into darkness.

9:13The water would begin corroding the tracks and the steel columns that hold up the roofs of these tunnels that would eventually cause the streets to collapse and allow the water to flood the city's surface too. Around 20 years are through our disappearance, with the kind of urban wetland forming into spurs with skyscrapers, but even they may not last very long. Now, this is not to say that skyscrapers aren't designed to withstand a lot. They have steel and concrete supports called piles drilled down all the way into the baroque to form their foundations. The tallest skyscraper in the world, the Burj Khalifa, has 192 of these. Each 1.5m in diameter and extending 50m down into the ground, they are well made. But the problem here is that no matter how strong they are, these steel foundations are not designed to be waterlogged all the time. And if they're surrounded by all those rivers I mentioned before, then water will infiltrate any minuscule cracks and force them apart even more.

10:17This especially happens in cold places because water expands when it freezes. This freezing thoring cycle creates the perfect condition for skyscrapers to topple within a hundred to 200 years. And as our concrete jungles collapse, what would replace them is the real thing. Plants are tougher than we often give them an credit for, and biological weathering is already a very real concern that we had to deal with in man-made environments. For example, in the Temple of Taprome in Cambodia, you can see huge deciduous trees with roofs that appear to swallow the temple itself. And in New York, several sidewalk trees show grit on par with New Yorkers themselves. This tree in West Chelsea, for example, has grown around the iron frame that was once put in place to contain it, leaving only small pieces poking out of the trunk. With no more weeding, the plants will most certainly take over our cities within just a few decades,

11:21infiltrating every microscopic crack in our pavements. Perhaps only the hardy as pioneer plant species like Lycan's and Mossas will colonise this new urban environment. But these will pave the way for others, and by the time we hit 500 years post-humans, cities like New York will resemble the once noble forest that helped the Lenape to prosper. But it's inside those forests where things get really interesting. Animals like rats, cop crotches, pigeons, raccoons, and even foxes have all adapted to thrive in urban habitats, often scrounging on human scraps and emerging at night when human activity is at its lowest. Since these species already make use of cities, it's likely that they would be the first proper city dwellers in a post-human world. They could survive on decaying food in our homes and supermarkets for a few months, at least, and would probably experience a bit of a population boom.

12:21But animals that have previously been kept on the fringes of cities like mountain lions or bears would also be free to invade. And with more large predators entering urban habitats, the success of the smaller city dwellers wouldn't last very long. Another species that would likely fare quite well there are domestic cats. Felis catas were domesticated from the Middle Eastern Wildcat, Felis Sylvestris around 12,000 years ago, and have always enjoyed a kind of double life as both the wild animal and a charismatic pet. As estimated, there are now well over 600 million of them around the world, and they've been introduced to every continent besides Antarctica. With so many domestic cats already present in habitats worldwide, they would have a major advantage over wild species in colonising the space we would have left behind. Cats could make use of those healthy rap populations, and could quickly revert to more feral behaviours in order to survive.

13:24Dogs could experience some of these same advantages, but they would likely be out competed by wolves, especially dogs that have undergone extreme selective breeding like pugs or British bulldogs. In our planet's most unusual cities, wild migrants may also be moving in. Gondalea-free, the canals of Venice will become calm, clear waters with no ores and other boat traffic stirring up sediment. So it's likely that marine mammals like dolphins could colonise the waters once more. We've already seen hints that this is possible. Back in 2021, Covid regulations drastically reduced boat use in Venice, which caused its waters to become clearer. The city was rewarded with a visit from a pair of striped dolphins, who swam in the Grand Canal until they were led by the Coast Guard back towards the open sea. But if similar visits were to happen in a post-human Venice, it might not actually be the best thing for the dolphins. The enclosed canals can be disorientating for them, as they attempt to find their way with their signature clicking sounds.

14:27I mean, perhaps these dolphin populations would even adapt and somehow learn to navigate the maze with ease. But it goes to show that dolphins could journey into Venice if they wanted to, and who knows, I mean it's a nice place. As for the rest of Europe, much of it used the host larger predators, like the Eurasian links, grey wolf, brown bear, Arctic foxes and even the Caucasian leopard. Many of these species also found themselves in conflict with humans, and as a result they've been lost from many of their original habitats, or persists in much smaller populations. But if humans weren't part of the equation anymore, these animals might be able to come back too. They'd be free to feast on our remaining livestock without fear of persecution, and expand their ranges throughout their old hunting grounds of Europe. So without humans we'd be looking at a boom in your least favourite city pests, a carnival comeback more grassland, and a return to prehistoric-looking landscapes.

15:32But without us to rule over this new world, which species might emerge to take our place? Would it finally be time for chimpanzees to reclaim their throne, living up the planet of the Apes in real time? Or could something else more unexpected come to the fore? The disappearance of humans would create a major vacuum in available niche space, creating the perfect opportunity for some other species to evolve to fill it and replace. So who are the most likely contenders? There are several possible answers to this question, and in fact some of the animals I've already mentioned could be up for consideration. It's even possible that humans 2.0 could evolve since our chimpanzee ancestors would still be around after we're gone. But there is one group we haven't talked about yet, a group that could stand a real chance of coming out on top. Insects have been described as evolutionary overachievers by many biologists. There are more than a million documented species, and they've been around for 350 million years, long within the dinosaurs or even flowering plants.

16:40They can be found in almost every habitat, even Antarctica, and outnumber the human population by 1.4 billion to 1. And with these impressive stats, it's fair to say that insects would be a contender for the rulers of the post-human world. So what is it about them that makes them so successful? Well it's easy to forget this, but insects were the first animals to evolve flight, and flew for up to 170 million years before anyone else. This makes insects naturally very good at dispersing throughout their habitat, which is a vital skill for finding food, mates, and shelter. Another win for the insects is the fact they have a very segmented body plan. There are usually just three segments, head, thorax, and abdomen, which are collectively called tag-matter. This is fundamentally similar between insects species, but it has huge evolutionary potential for diversification. Think about it, small evolutionary changes to each segment could be enough for a new species to be created, and there are millions of additions and configurations to explore.

17:47Each adaptation could give the insect a new ability, whether it's making use of a specific food source, exploiting a new habitat, or even finding a mate more successfully. They are perfect for adapting to an environment without us. Finally, insect development involves metamorphosis. Insects can have several developmental stages punctuated by moths, where they shed their exoskeleton and emerge into a new form entirely, and this accomplishes several things. Firstly, each developmental stage often has its own unique food sources, meaning there is less competition between members of the same species. This supports larger overall population sizes, and it also means that during pupil stages, when the insect is protected by a cocoon, it can wait out tough conditions until the outlook for survival gets better. Essentially having several developmental stages allows each insect to occupy several different niches throughout its lifetime, so basically it can get the best of every lifestyle.

18:52For these reasons, many experts have backed insects as the next most successful group after humans, but evolution takes time, and given there might be some climate upheaval, like when we'll get into that in a second, it could take millions of years for them to completely flourish. The other issue is that although insects may experience success on par with humans, they're unlikely to share our intelligence, so we can't really say they'll take our place. So which species can match us in this regard? Well, measuring intelligence is a tricky business, since we humans have historically tried to use our own brain power as a yardstick to measure everything else against. But that isn't necessarily the best gauge, as different animals perceive the world and interact with it in different ways, which then also affects their intelligence. This is nicely demonstrated by the octopuses. Octopuses are weirdly similar to humans in some ways. We both have camera type eyes that focus light in the same way, and we share the same bilateral symmetry.

19:56But unlike humans, octopuses obviously have eight arms, which are controlled in an unusual way. Unlike us and our centralized nervous systems or brains, two-thirds of an octopuses 500 million neurons are found in their limbs. This decentralizes their nervous systems and their processing power, allowing octopuses to control each one of their arms semi-independently, like eight mini brains, if you like. Researchers shown that this body plan helps octopuses to perform complex behaviors from tall, used tube camouflage. It's almost like having a sort of built-in intelligence. So, octopuses would definitely be up there as some of the cleverest animals in a post-human world. But what would they do with this intelligence? Let's head to the waters of Jarvis Bay in Eastern Australia. When we find the example of the impressive feats, octopuses are capable of. Dubbed Ock Lantis by the researchers that discovered it, the Jarvis Bay site is home to 15 individuals that have meticulously arranged their dens made out of scavenged shells.

21:04Here, they live, communicate with each other, fight for territory and mate. This was an especially exciting discovery, as the species in question, the gloomy octopus, was thought to be a bit of a loner. But this octopus city shows that they are capable of complex social interaction in the wild and have capacity for human-like intelligence. So there we have it, the dawn of insects, rule and underwater Ock Lantis. The post-human world is certainly going to deliver. But one question still remains, what kind of climate are they going to deliver in? In my opinion, we've saved the best and arguably most important stuff to last. With us not being around to mess things up, do the climate systems that hang so delicately have a chance of fighting back? Or is the damage already done? One final parting gift from humanity. Our climate is influenced by so many factors. Some, like the most recent ones, can be traced back to humans. Considering the sheer number of us on the planet, 8.3 billion, and the scale of industries like farming, transport, energy and manufacturing, we're bound to leave behind traces of our presence for the post-human world.

22:16The National Oceanic and Amismaric Administration states that carbon dioxide levels have risen by 50% since 1800, hitting 431 parts per million in April 2026. No attributes this increase may need to human activities like extraction and burning of fossil fuels. But if we weren't here anymore, then these drivers would naturally stop. Problem solved? Not quite. This probably wouldn't make an immediate difference to the climate. There's a term used by climate scientists called committed warming, and basically includes any global warming that results from the greenhouse gas emissions that we've already released, even if we disappeared tomorrow and stopped releasing them. So climate change would technically continue. And experts predict it would take thousands of years for CO2 concentrations to return to pre-industrial levels. This is because the ocean is like a big carbon sponge. It can absorb carbon dioxide when it dissolves into the water or enters the ocean from the soil.

23:19But it takes a while for this carbon to get absorbed into the deepest depths of the sea. So patience is key. Regardless of our influence on the climate, the post-human world is probably heading for another ice age. Now we are technically of course in an ice age already since there is still ice at the poles. But experts think the ice could spread much further than this in the future. Under natural conditions, some study suggests a major glaciation could begin within roughly the next 50,000 to 100,000 years, although the committed warming we've talked about may delay this significantly. A long term cooling trend began on Earth around 6000 years ago, resulting from changes to Earth's tilt, orbit-shaped and wobble, also known as the Malenka-Vitch cycles. However, human-driven emissions have now overwhelmed much of this natural cooling trend. So with no fresh human emissions being pumped into the atmosphere, these cycles would probably reassert their cooling effects far sooner than they would have otherwise.

24:21And then an ice age seems to be just around the corner for those species we left behind. So good luck to the insects and the octopuses. It might be time to wrap up one. With cities destroyed and Earth covered in ice, it appears that from above at least all traces of humanity would be gone in perhaps as little as a few thousand years. But as we've already discovered, our impact runs deeper than that. Just as today we find fossilized dinosaur bones, we will leave behind our own rock record, and not just bones either. Instead, a layer of plastic and so-called techno fossils marking our impact on the planet for millions if not billions of years to come. Eventually, even that will be lost as it's gradually recycled into the Earth's mantle thanks to shifting and subducting tectonic plates. But as currently the oldest rocks in the world sit at 4.4 billion years old, it's likely that our geological history might remain for some time.

25:25And by that point, the Sun might have scorched the planet anyway, although that's a story for another day, when you can actually watch our last-dramned space after this if you want. For now, we've come to the end of our little thought experiment, and I hope you aren't feeling too spooked by our fictional disappearance. Personally, I've quite enjoyed watching the Earth from the Void, and seeing all of the remaining animals fight to claim our vacant lands. For now, we live in the Anthropocene, a geological epoch that is literally named after the humans and the huge influence we have had in shaping our environment. So, there's no doubt that our disappearance would promote some major reshuffling of the life we leave behind. As Alan Weisman said when he was asked about his motivations for writing his book, looking at what would happen in our absence is another way of looking at what goes on in our presence. And from the information we presented in this video, it's harder to deny that we humans have earned our title as the defining force of the current era. And that our legacy for better or worse will endure long after we're gone.

26:30Let me know in the comments what you think Earth would look like without us, and particularly which animal you'd like to see take our place. Personally, I'm Tim Octopus. Thanks for watching, and we'll see you in the next one.