Take a look out your window. Trees sway lazily in the breeze. Birds glide effortlessly through the air. A closer look reveals ants marching dutifully down the sidewalk. Life is all around you. Now picture that same scene, but with three-quarters of those plants and animals dead. Depressing, huh? Well, it turns out that this reality might not be as far-fetched as you might think. It's happened before and it may happen again. The question is: Will you be ready?
Extinction itself isn't really a big deal. It's happened for millions of years at a natural pace scientists call the background extinction rate. But when a variety of plants and animals from all over the world start going extinct at a much faster pace than the background rate, that IS a big deal. Scientists label such events mass extinctions.
Over the past 500 million years, five mass extinctions (collectively known as "The Big Five") have resulted in the extermination of more than 75 percent of species living at the time, typically in a span of less than 2 million years [source: Newitz]. Basically, natural phenomena like meteor strikes and atmospheric changes altered Earth's climate a lot faster than most plants and animals could adapt. The one you're probably most familiar with is the Cretaceous event, which occurred about 66 million years ago and was responsible for killing off the dinosaurs [source: Natural History Museum of London]. Now scientists believe we are in the early throes of a sixth big mass extinction, largely of our own making.
OK, so a bunch of plants and animals die off. Why should we care? Well, plants and animals do a lot of things for us, from cleaning our air and water to pollinating our crops. Given our complex relationships with other living things, no one is really sure what might happen given a significant loss of biodiversity, or variety of life, on Earth. But it's likely to be unpleasant at best and catastrophic at worst.
Will we survive? Maybe. Perhaps we can get some pointers from animals that have survived past mass extinctions. Maybe we can invent our way out of any problems we encounter. It might even be possible to head the whole thing off before it gets worse. It all depends on how things play out.
Past Mass Extinctions
To get a better sense of what a mass extinction might look like (and how we might survive it) let's explore the ones that have already happened. Hope you're sitting down because this is some pretty intense stuff.
As we mentioned earlier, we've had five big mass extinctions up to this point [source: Barnosky et al.]:
- The Ordovician event: ended 443 million years ago; killed about 86 percent of all species
- The Devonian event: ended 359 million years ago; killed about 75 percent of all species
- The Permian event: ended 251 million years ago; killed about 96 percent of all species
- The Triassic event: ended 200 million years ago; killed about 80 percent of all species
- The Cretaceous event: ended 65 million years ago; killed about 76 percent of all species
That's a lot of death. But what could create such mass devastation? The causes for these events read like the scariest apocalypse novel you could imagine. Volcanic eruptions, meteor impacts, global temperature swings, and changes in the composition of both the atmosphere and oceans are all to blame for one mass extinction or another. Even scarier: While most of these die-offs took place over thousands or even millions of years, the Cretaceous event may have wreaked its havoc in the span of mere months.
Take the Permian event, which is morbidly referred to as "The Great Dying." According to one explanation, this extinction began some 252 million years ago when Earth boasted one huge landmass known as Pangea [source: Natural History Museum of London]. Global temperatures were higher than ever, making the continent's interior desert intensely hot and dry. Life was barely hanging on.
Then, one of the largest volcanic eruptions in history began, covering huge swaths of land in lava and spewing massive clouds of ash and toxic gasses into the air. After a short period of acid rain and global cooling, the entire planet began to warm in a big way. Carbon dioxide from the volcanoes filled the atmosphere and created a greenhouse effect. After 160,000 to 2.8 million years of devastation (a long time by our standards, but not Earth's), 96 percent of all species were extinct [source: Barnosky et al., Natural History Museum of London].
Obviously, surviving a mass extinction won't be a walk in the park.
Signs of a Future Mass Extinction
To the regular Joe on the street, it doesn't seem like we're in the midst of a mass extinction. Even experts admit that only 1 or 2 percent of all species have gone extinct in the past 200 years [source: Pappas]. That's a long way from the 75 percent needed to join the mass-extinction club. So what's gotten scientists worked up?
If you'll recall from earlier, a mass extinction can occur when plants and animals start dying off a lot faster than the normal, or background, rate. So a great way to see whether we're headed toward such an event is by looking at the current extinction rate versus the background extinction rate. And sure enough, a number of studies have done just that.
One of the more pessimistic findings estimates that the background rate of extinction for all species is 0.1 extinctions per million species per year (E/MSY), while the current rate is more like 100 E/MSY. That would mean we're losing species 1,000 times faster than normal [source: Orenstein]. Yikes! A more optimistic study, which looked only at mammals, pegged the background rate of extinction at 1.8 E/MSY, and the current rate at 50 to 75 E/MSY. But even in that supposedly rosy scenario, the current rate is at least 27 times too high [source: Simons].
What, then, is causing all of this? One problem is habitat loss. As the global population expands, more land is being cleared for farming, leaving less room for the creatures that lived there before. Another big issue is that many species are being driven to near extinction for short-term economic gain (think poaching and overfishing).
The explanation receiving the most attention, however, is human-caused climate change: When we burn fossil fuels, carbon dioxide is released into the atmosphere where it traps heat from the sun and causes the planet to warm. Some plants and animals just can't adapt fast enough to the changing environment and are dying off as a result [source: Barnosky].
If we are indeed experiencing a mass extinction, that doesn't mean we're goners. Plenty of creatures have survived before.
How Animals Have Survived Mass Extinctions
Survivors of mass extinctions are in a pretty elite club. And unlike today's doomsayers, they didn't have guns, bomb shelters or food storage to help them out. What is it they were doing right?
To answer this question, let's look at Lystrosaurus, one of the greatest survivors of all time. This creature was a part of the lucky group that survived the Permian event, which, if you recall, killed 96 percent of all species on Earth. Especially surprising is that Lystrosaurus wasn't a tiny algae or insect: It was a mammal-like reptile about the size of a pig, basically the only animal of its kind to dodge extinction.
Lystrosaurus had a number of things going for it. One was that it was a burrower. As any survivalist worth his or her salt can tell you, underground is a pretty good place to be when something bad happens. Plus, breathing underground was good form during the Permian event, when low oxygen levels and dusty airborne contaminants became the norm.
Another tool in Lystrosaurus's survival kit was its ability to move and spread out over great distances. When things got bad, the creature was evidently capable of waddling to safer climes, eventually inhabiting areas all over Earth's super-continent, Pangea. And how was it able to adapt to so many places? A big reason is that it was a generalist species, meaning, among other things, that it wasn't a picky eater. Although it ate only plants, its beak-like mouth was equally effective at chomping down rough vegetation and digging for roots.
Other species have survived mass extinctions by virtue of their small size. Obviously, little creatures don't need as much food as their larger counterparts (think mice versus elephants). They also tend to reproduce more, which gives them a larger, more genetically varied population that can adapt more quickly and effectively to change.
In a lot of ways, mass extinction survival just came down to luck. Certain species had certain traits that helped them endure whatever awful things befell the Earth. So is the survival of the human race really just a game of chance?
How Humans Can Survive a Mass Extinction
When most people think about survival, they think about things like personal protection, emergency shelters and food preservation. Sure, that stuff might help in the short term, but this is a mass extinction we're talking about! You can't dehydrate enough food to last 2 million years! Instead, it's going to take some serious, long-term changes in human behavior and technology to survive something like that.
While humans have never had to survive a Big-Five-style extinction, we certainly have displayed some qualities needed to do so. Remember Lystrosaurus, which was able to spread across the globe and adapt to various climates and food sources? We did that, too — 60,000 to 130,000 years ago [sources: National Geographic, Rodgers].
Members of the Homo sapiens species departed their African homeland, eventually inhabiting almost every continent [source: National Geographic]. Guesses about what spurred this migration range from massive drought to a volcanic eruption [sources: Gugliotta, Newitz]. Regardless of what happened, this example shows that even if hardship forces us to pack up and move, we can still survive and even flourish.
Of course, our greatest advantage over all previous species is — you guessed it — technology. What if the climate begins killing our crops? Perhaps we can genetically engineer our food to be hardier. What if a large asteroid is on a collision course with Earth? Maybe we can land a spacecraft on it and push it away. Some of the most fascinating extinction-dodging research is in geoengineering, a field in which scientists study ways to control our climate with technology. Imagine floating arrays of mirrors that deflect sunlight to cool the planet, or artificial trees that pull carbon dioxide out of the air and inject it underground. As crazy as it sounds, these and other solutions are possible, and they might even work.
But what if they don't? There's only one other option, really, and that's to go live somewhere else. Not another city, country or continent, but another world entirely. Scientists have long dreamed of building structures designed to mimic Earth's conditions on other planets, and some have even suggested that we could geoengineer the whole planet to function like our own.
But before we wander too far into sci-fi movie territory, let's have a reality check. Do we really want to rely on untested technology to save us? Perhaps, as the next section suggests, we should try to prevent this sixth big mass extinction from getting even worse.
How to Prevent a Mass Extinction
All that geoengineering stuff sounds pretty amazing, but it raises some real concerns. For one, there will almost certainly be unintended consequences from large-scale climate experiments. But perhaps just as troubling is that we, as a society, might start counting on scientists to bail us out when we might be better served taking action on our own. After all, if all of us are nudging the Earth toward a mass extinction, shouldn't we all be part of the solution?
If we're going to try to stave off a mass extinction, the first thing we need to do is address human-caused climate change. Some scientists think we may have already passed the point of no return, but a 2014 report by the United Nations' Environment Program and the World Resources Institute suggests there is still a glimmer of hope. In order to hold global warming under 3.6 degrees Fahrenheit (2 degrees Celsius), the standard they set to avoid dangerous climate change, we need to reduce greenhouse gas emissions by a daunting 50 percent by 2050 [source: Sheridan].
How? For starters, combine trips in your car. Buy more efficient cars. Adjust your thermostat down in the winter and up in the summer. Bike to work. Recycle. These may seem like small changes, but if everyone pitched in, the effect could be huge [source: Barnosky]. Take something as simple as a light bulb: If every American replaced one incandescent bulb with an Energy Star-rated one, the reduction in greenhouse gas emissions would be equivalent to taking 800,000 cars off the road [source: EPA].
Another extinction-maker is habitat loss. Now I like a juicy hamburger as much as the next carnivore, but reducing meat consumption would help out in a big way. Crops provide more calories per acre than livestock, so you can feed more people with less land. That's because you need land to grow livestock feed in addition to the land needed to pasture the animals [source: Oremus].
Finally, there's the problem of poaching and overfishing. Don't buy products that come from endangered species (like ivory) and try to purchase seafood from sustainable fisheries. For a little guidance, hop over to the IUCN Red List to search for endangered species and the Monterrey Bay Aquarium Seafood Watch to find seafood recommendations.
In the end, no one is sure how much we can do at this point. We've already changed our climate so much that these steps might only delay the inevitable. But to state the obvious: We're either going to have to try to prevent a mass extinction or cope with it. Here's to hoping we can make Lystrosaurus proud.
Author's Note: How to Survive a Mass Extinction
I can't think of a heavier topic than mass extinction. Pondering the death of 75 percent of all species on Earth, possibly including your own, is a harrowing task for any author with a healthy sense of self-preservation. But among all the bad news, I think there are some positive things to take away from this article. Humans have always shown an incredible capacity to persevere when disaster strikes. And what's more, there are a lot of really smart people who are already thinking of ways to ensure our survival. Perhaps the alien race who discovers the smoking rubble that was planet Earth will read this sentence and laugh, but I don't think we'll go down without a fight.
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