250 million years ago, 95% of life on Earth perished, probably from megavolcanoes. 65 million years ago, a meteor strike destroyed the dinosaurs. Now, some say another mass extinction is underway. Scientists tell you how to survive it.
Underground City by Gamefan84
Most scientists agree that there are five known mass extinctions on Earth, where many or most species of life were extinguished – usually by a sudden shift in climate or the composition of the atmosphere. Often, cataclysmic events help these extinctions along. A comet smashes into the planet, or megavolcanoes spew poison into the environment for a thousand years. There is also an ongoing debate about whether humans may be ushering in a sixth mass extinction through pollution, overhunting, and global warming.
If humans are causing a mass extinction, it will probably resemble a slow-motion version of the megavolcano scenario, where carbon, sulfur, and methane choked off the lives of plants, animals, and even insects. As we heat up the oceans, frozen deposits of methane beneath the water will melt and turn the atmosphere toxic, along with the carbon we've already put there by burning fossil fuels. However, we might also suffer a mass extinction that has nothing to do with our polluting ways. There are several megavolcanoes on the planet that could go off at any time, and we've not immune to roving asteroids or comets either.
But enough about mass death. The most important lesson we can learn from mass extinctions of the past is how to survive. I spoke with several scientists, from geologists to zoologists, to find out what makes for a mass extinction survivor. The good news is that humans have some of the characteristics required to survive. The bad news is, depending on what causes the extinction event, we may be doomed anyway.
Go underground (or underwater)
Scientists agree that three basic things unite the creatures who survive mass extinction: They're small, they're widely dispersed across the globe, and often they live underground. Being underground was especially helpful during the end Cretaceous extinction, when the dinosaurs were killed off by a huge meteor hitting the planet. The impact hurled massive amounts of molten rock and toxic particles into the atmosphere, blanketing the planet in heat, then cold.
UC Berkeley biologist David Wake, curator of the Museum of Vertebrate Zoology, told io9:
Subterranean animals have the best chance of surviving a cosmic event — salamanders spend much of their time below ground and the seem to have been largely unfazed by whatever event or events led to the end Cretaceous extinction, which many think might have been caused by an impact by a celestial object.
During the "great dying," or the end Permian mass extinction 250 million years ago, being underground or deep beneath the ocean was basically mandatory for survival. In fact, one of the only creatures to make it through this catastrophic era when megavolcanoes poisoned the atmosphere was the humble, pig-like Lystrosaurus. These tusked creatures probably spent a lot of time rooting underground for food, making them ideal survivors in a world where surface life died out and the air was full of dust.
So rule number one of mass extinction survival is to find an underground or underwater city, stock it with food, and wait for about a decade before poking your head out. There are at least 200 underground cities in Turkey, built between 500-1000 AD by Christians hoping to evade persecution during the Byzantine era. One of the biggest of these, Derinkuyu, could hold up to 35,000 people plus food storage and wine-making facilities. These ancient cities might be the best hope for the future in a mass extinction event.
If you can't live underground, going into stasis can help too. Yale biologist Ellen Thomas, editor of Marine Micropaleontology, explained:
Oceanic algae (which are generally microscopic) survived [if they had] a 'cyst' phase, a life stage in which a cell can survive darkness, heat, cold and possibly acidification of the ocean . . . Cysts will fall to the sea floor and just survive a period of non-activity, then revive when conditions become more normal . . . Plants on land survived which have resistant seeds, or bulbs and roots which can survive for a long time through a fire and period of darkness.
Though we haven't perfected a way to put humans in stasis, a future society threatened with extinction might choose to store thousands of people in cryosleep deep underground to prevent homo sapiens from dying out. Especially if we don't yet have space colonies.
Disperse, adapt, and think small
The most hardy creatures on Earth are ocean-dwelling cyanobacteria, or bacteria that survive via photosynthesis. Thomas said, "Cyanobacteria have survived since shortly after the origin of earth, and have survived all mass extinctions since." These bacteria are survivors because all they need is light from the sun – they can survive in highly acidic conditions, without oxygen, and even (sometimes) in the vacuum of space. Cyanobacteria teach us one lesson: Be adaptable. Of course that's easy for a bacterium who is equally comfortable with oxygen or methane. How do mammals like us adapt?
Earth scientist Mike Benton, who has studied the end Permian extinction event for over a decade, explained:
I think general biological principles suggest that good survival characteristics for any animal are smallish size, generalised diet, and broad ecological tolerance. This is why elephants (large, small population sizes, need for huge territory for food) and pandas (limited diet and environmental range) are at threat of extinction, whereas rats, cockroaches and humans probably are not.
Evidence from mass extinctions of the past is that the initial killing is often quite random (the 'field of bullets' model), and so nothing in particular can protect you, but then in the following grim times, when earth conditions may still be ghastly, it's the adaptable forms that breed fast and live at high population size that have the best chance of fighting through.
So Benton thinks we have a fighting chance, because we can adapt to new territories and eat a wide range of things.
Thomas added:
Small animals may have survived on land when they lived, for instance, in burrows so that they could escape a heat flux from the asteroid traveling through the atmosphere, fires, cold and darkness and super-acid rain. It of course helped if they were eating seeds, roots and burrows. Animals which eat fresh vegetables went extinct.
Humans would have a difficult time surviving on tiny amounts of tubers and worms. Luckily, algae seems to bounce back from mass extinction pretty quickly, so we might be eating a lot of that along with our roots and seeds.
Still, humans may be just too large to survive. According to Thomas, all animals of more than about fifteen pounds went extinct after the cosmic event that ended the Cretacious and the reign of the dinosaurs. Top predators on land and sea usually died off first, because the animals and plants they ate also died out during the toxic cold that seems to accompany most mass extinctions. "Humans are predicted to have problems in a mass extinction," said Thomas. "We're too big."
Underwater city by Anez Erynlis
A few final tips on dealing with mass extinction
Whether our mass extinction is caused by global warming or a more dramatic catastrophe, we'll be coping with a toxic environment where temperatures may be extreme.
Here are some takeaway lessons from our crash course in mass extinction survival:
1. Burrow underground or build an underwater city to shield you from the elements.
If we can't hibernate for a few centuries, we're only going to survive a mass extinction by moving into modern versions of the Turkish city Derinkuyu. We'll need massive underground complexes - perhaps like the huge underground mall in Montreal - where we can grow food and produce our own energy. We'll need air shafts with purification systems built in, and perhaps even a way to make oxygen. But most of all, we need to be prepared. Let's start building our underwater cities and subterranean farms now, before it's too late. And hope they don't turn out like the infamous science fictional cities of Ember and Rapture.
2. Don't show your face for a while
As Thomas points out, the difficult thing is to know when to poke your head back up for air. The good news is that even if we have a major asteroid impact, "we're really only talking cold at short time scales – maybe a decade." The trouble is that our asteroid may hit coal, oil, or limestone, all of which would evaporate into atmospheric poison that might take hundreds of thousands of years to cycle out of the environment. There are even some scenarios where our ocean might go anoxic – lose all its oxygen – and kill most creatures in the oceans. Indeed, a small anoxic event is already underway near the Deepwater Horizon plume, where huge microbial blooms that eat fossil fuels are sucking all the oxygen out of the water. They're killing other creatures who need oxygen to live.
So what do we do while we're waiting for the Earth to be habitable again? One thing for certain is that we won't have to stay buried for millennia at a time – even with a toxic megavolcano in the works. "There would be intervals where you could get out, certainly away from the location of the volcano," Thomas said. A worst case scenario would probably be nuclear winter, where radioactivity would require at most a thousand years underground. That's nothing in geologic and evolutionary time!
3. Change your diet.
Don't expect to have leafy green vegetables or any tasty creatures who live above ground. Get used to eating very little, and expect most of your diet to come from underground or from green algae.
4. Don't panic.
Humans are resourceful creatures. If Lystrosaurus could survive the end Permian event, we can survive whatever space or climate change throws at us. We may not be small, but we are adaptable and widely dispersed over the planet's surface. Even the most catastrophic event might not be enough to stop us.
Annalee Newitz is the author of Scatter, Adapt and Remember: How Humans Will Survive a Mass Extinction.