Species loss is real threat, but what would a mass extinction event look like? How would we be affected? Biologist Joseph Levine looks at a future where less biodiversity has a very real effect on humans.
The movie After Earth (2013, directed by M. Night Shyamalan) takes place following a massive planetary extinction event and various other calamities that have forced humans to flee the planet. The film begins 1,000 years after humanity’s departure. The remaining organisms have evolved to treat humanity as a hostile threat.
Parts of the film were shot on the grounds of the Organization for Tropical Studies (OTS) (www.ots.ac.cr) in Costa Rica, a center for research on biodiversity, tropical ecology, and climate change. The film’s producers asked Joseph Levine, a biology educator, text-book author, and course director at OTS, to create an educational Web site, http://www.lifeafterearthscience.com, to help students understand the film’s backstory. I asked him about the science behind the After Earth scenario.
THE FUTURIST: There’s evidence that we may be on the verge of a mass extinction event as large as the Permian extinction that took place millions of years ago. What would a mass extinction event actually look like if it occurred today?
Joseph Levine: When people hear “extinction” they usually think of endangered species such as white rhinos, or pandas. That’s fine, because it’s a tragedy when any species disappears. But a mass extinction is very different, and much more serious. During a mass extinction, environments change so radically, and so many species disappear, that entire ecosystems collapse. And that’s important because healthy, functioning ecosystems provide very important services that the general public generally takes for granted.
For instance, terrestrial ecosystems do a fabulous job of catching and holding rainwater, purifying it, storing it, and providing us with clean fresh water. Ecosystems also provide habitats for pollinating organisms to live in. You’ve probably caught wind of the problems we’re having with local pollinating insects. That’s not pleasant to think about, because almost all plants that we rely on for food, other than grasses, are pollinated by bees or mosquitoes or bats or some other organism. Those pollinators need some place to live—and that’s another service ecosystems provide.
The danger is that a bunch of economic drivers of global change are whittling away at the resilience and stability of the ecosystems on which we depend for those kinds of services. If those ecosystems collapse, the services they provide will disappear.
THE FUTURIST: When these biological systems start to collapse, it’s not something that will show up on the news. But it actually affects the way consumers live in highly developed countries, and even in cities, right?
Levine: Yes. One great example involves the metropolitan area of New York City and its watershed north of the city in New York State. Talk about a futurist! Whoever was clever enough to set aside enough watershed back then to supply New York City now was an incredible genius. Thanks to that foresight, New York City has always had some of the best, most reliably clean drinking water of any major metropolitan area in the world.
That watershed area is under constant pressure for development of various kinds—industrial development, roads, residential development with septic systems, larger municipal sewage treatment facilities, and so on.
A while ago, there was a plan to open up larger tracts within that watershed to more intense development. But people were intelligent enough to study the likely effects of that kind of development on the ability of that watershed to provide New York City with the water it needs.
The city’s planners and researchers discovered that development in the watershed area would produce all sorts of tax revenues and other economic benefits. But the loss of ecosystem services from that kind of development would require the city to invest trillions—not even billions, but trillions—of dollars into a whole new range of water treatment plants, because the water would no longer be as dependably clean as it has been.
We don’t normally think about services like that. The watershed ecosystem’s work, in terms of collecting, storing, and purifying water, is invisible to us, because it happens underground. We don’t think about what goes on underneath the roots of forests and beneath the sand and around the reservoirs. But those processes are very important.
That’s just one kind of ecosystem service that affects people. For instance, if populations of pollinating animals continue to drop, it’s hard to conceive of what we would do. Again, human inventiveness and creativity are amazing. It’s possible that, if the threat to pollinators came from disease, or just temperature, or something like that, we might be able to breed a new, resistant strain of pollinators. But if pollinators’ habitat disappears, we might need to maintain them artificially, the way that some farmers have for quite some time—carrying hives of European bees around the country, from one area that needs pollination to another. To do that for all farmers’ pollination needs, for all crops, everywhere, would involve a staggering amount of work.
THE FUTURIST: Let’s talk about the Anthropocene, a term that’s in some of the videos on your site. My understanding of the Anthropocene is that it refers to an entirely new epoch—one not driven by natural cycles, like every previous epoch in the Earth’s history, but by human influence. This is why the prefix anthro,or human-made, defines this new epoch. In a post-human scenario like in this movie, how do you think about the effects of humanity on diversity, after the departure of humanity? How does post-human evolution differ from what we understand about pre-human biological evolution?
Levine: The term Anthropocene is not yet universally accepted, but it’s being actively promoted in a growing number of scientific circles. There really is something to this idea that our species—our single species—has now become the most powerful force for change on the planet. We are a globe-changing force. We move unbelievable amounts of materials. We transform vast quantities of energy. We harvest enormous quantities of primary production from different parts of the planet. “Primary production” means the solar energy that’s captured by photosynthetic organisms and then used to produce either plant material or, ultimately, animal material that we consume, or other resources that we consume that are based on biological processes.
That’s what’s important about the Anthropocene. But if we accept the existence of the Anthropocene, it would not be the first time that any organisms have changed global environments.
Consider this: Oxygen is generated by photosynthesis. When plants first evolved photosynthesis billions of years ago, the Earth’s atmosphere had very, very little free oxygen in it. The process of photosynthesis itself is what gives us the concentration of oxygen that we now have in the atmosphere. To living systems, oxygen is a highly powerful oxidizing (or rusting) agent, so when oxygen levels reached a certain point, organisms had to evolve protection from the destructive effects of this highly reactive gas. A whole bunch of organisms couldn’t do that, and went extinct. A bunch of other organisms that once lived on the surface are now found only in places like deep mud where there isn’t any oxygen.
So living things have changed the planet in the past. But this would be the first time that one single species has caused such dramatic change. And again, the issue here is the rate of change—the speed at which we’re transforming the planet. The fact that we can measure changes in a single human lifetime—and certainly since the beginning of the Industrial Revolution—that is unprecedented. That’s overnight in biological, geological, and ecological terms. It’s so fast that organisms and ecosystems don’t have time to adapt to changes. Many people don’t have an appreciation for the difference between the speed of human-caused change and the much more gradual, natural change that occurs over what geologists and evolutionary biologists call deep time, millions of years. How many people really stop to think about that?
THE FUTURIST: So in a post-human Earth—this is a question entirely out of ignorance—which of the species would be the most successful? Would we see a return of big, predatory megafauna, like lions, crocs, and wolves, that are close to extinction today? Or would these invasive species that, today, enjoy a symbiotic relationship with us—like rats, pigeons, and cockroaches—would they continue to spread and overwhelm the rest of the ecosystems that they’re in?
Levine: Well, I can refer you to one person’s thoughtful reflection on that question. Dougal Dixon’s book After Man: A Zoology of the Future (St. Martin’s, 1998) is worth looking over. He arrived at his hypothesis after looking at the kind of species that do, in fact, survive mass extinctions. Survivors of mass extinctions tend to be what biologists call ecological generalists—or what most people refer to as weeds. A weed is anything that grows someplace you don’t want it. But in ecological terms, a “weedy” species is one that has high tolerance for extremes of temperature, extremes of water availability, and that kind of stuff. They’re almost indestructible organisms that live everywhere and reproduce quickly. And a lot of those are the kinds of species that are pestilential for us—cockroaches, rats, mice, starlings, crows in some places, cats in some places, dogs in other places. Dixon used those “weedy” criteria to select current species, and then he imagined how they might evolve over millions of years. What he came up with is entirely fictitious, but it’s one person’s intriguing way of looking at what might happen.
In After Earth, the characters played by Will and Jaden Smith—Kitai Raige and his dad—get shipwrecked on Earth 1,000 years after humans left. The film is science fiction. It would not be entirely impossible for organisms to evolve some characteristics of the imaginary critters in After Earth. But it would take a lot more than 1,000 years for multicellular animals—things other than bacteria—to evolve major changes. That is like the blink of an eye in evolutionary terms.
But all good science fiction has elements of science and elements of fiction. I don’t see a problem with that. I’ve loved science fiction since I was a kid. I started reading it because my dad used to read copies ofAmazing Stories magazine and Fantasy & Science Fiction magazine around the house.
The value I see in sci-fi is in getting people intrigued with an idea about the future through fiction in a way that gets them to look for the elements of truth behind the story. That was the approach that we took to the Web site.