Scientists recently modeled a range of interactions between energy-intensive civilizations and their planets. The results were sobering.
Remarkably, science has now advanced to point where we can take a first step at answering this question. I know this because my colleagues and I have just published a first study mapping out possible histories of alien planets, the civilizations they grow, and the climate change that follows. Our team was made up of astronomers, an earth scientist, and an urban ecologist.
It was only half-jokingly that we thought of our study as a “theoretical archaeology of exo-civilizations.” “Exo-civilizations” are what people really mean when they talk about aliens. Astronomers refer to the new worlds they’ve discovered as “exoplanets.” They’re now gearing up to use the James Webb Space Telescope and other instruments to search for life by looking for signs of “exo-biospheres” on those exoplanets. So if we have exoplanets and exo-biospheres, it’s time to switch out the snicker-inducing word “aliens” for the real focus of our concerns: exo-civilizations.
Of course, we have no direct evidence relating to any exo-civilizations or their histories. What we do have, however, are the laws of planets. Our robot emissaries have already visited most of the worlds in the solar system. We’ve set up weather stations on Mars, watched the runaway greenhouse effect on Venus, and seen rain cascade across methane lakes on Titan. From these worlds we learned the generic physics and chemistry that make up what’s called climate. We can use these laws to predict the global response of any planet to something like an asteroid impact or perhaps the emergence of an energy-hungry industrial civilization.
To launch our science of exo-civilizations we started with those laws of planets, building the right equations to capture the intertwined evolution of a planet and its young civilization. But planetary laws of physics and chemistry only tell part of the story. If we want to know the possible fates of other civilizations on other worlds, we had to bring some biology to bear too.
Population biology was a radical new field back in the early 20th century. Rather than just collecting statistics to describe animal populations, a few ambitious researchers like Alfred Lotka wanted to create basic mathematical models of things like predators and prey to predict the evolution of their linked populations. Predators (like wolves) eat prey (like bunnies) so they can make more wolf babies, thereby increasing the wolf population. Bunnies do a fine job of reproducing on their own, but if too many are eaten, their population numbers suffer. Today, population biologists, ecologists, and their compatriots use mathematical models to study everything from the spread of disease to the propagation of invasive species. The approach has even found its way to the study of human civilizations, including their collapse in places like Easter Island.
So, what did the model tell us? We saw three distinct kinds of civilizational histories. The first—and, alarmingly, most common—was what we called “the die-off.” As the civilization used energy, its numbers grew rapidly, but the use of the resource also pushed the planet away from the conditions the civilization grew up with. As the evolution of the civilization and planet continued, the population skyrocketed, blowing past the planet’s limits. The population, in other words, overshot the planet’s carrying capacity. Then came a big reduction in the civilization’s population until both the planet and the civilization reached a steady state. After that the population and the planet stopped changing. A sustainable planetary civilization was achieved, but at a high cost. In many of the models, we saw as much as 70 percent of the population perish before a steady state was reached. In reality, it’s not clear that a complex technological civilization like ours could survive such a catastrophe.
The second kind of trajectory held the good news. We called it the “soft landing.” The population grew and the planet changed but together they made a smooth transition to new, balanced equilibrium. The civilization had changed the planet but without triggering a massive die-off.
The final class of trajectory was the most worrisome: full-blown collapse. As in the die-off histories, the population blew up. But these planets just couldn’t handle the avalanche of the civilization’s impact. The host worlds were too sensitive to change, like a houseplant that withers when it’s moved. Conditions on these planets deteriorated so fast the civilization’s population nose-dived all the way to extinction.
You might think switching from the high-impact energy source to the low-impact source would make things better. But for some trajectories, it didn’t matter. If the civilization used only the high-impact resource, the population reached a peak and then quickly dropped to zero. But if we allowed the civilization to switch to the low-impact energy resource, the collapse still happened in certain cases, even if it was delayed. The population would start to fall, then happily stabilize. But then, finally and suddenly, it rushed downward to extinction.
The collapses that occurred even when the civilization did the smart thing demonstrated an essential point about the modeling process. Because the equations capture some of the real world’s complexity, they can surprise you. In some of the “delayed collapse” histories, the planet’s own internal machinery was the culprit. Push a planet too hard, and it won’t return to where it began. We know this can happen, even without a civilization present, because we see it on Venus. That world should be a kind of sister to our own. But long ago Venus’s greenhouse effect slipped into a runaway mode, driving its surface temperatures to a hellish 800 degrees Fahrenheit. Our models were showing, in generic terms, how a civilization could push a planet down the hill into a different kind of runaway through its own activity.
We need to put in more detailed and realistic climate physics. We also need to include the full range of energy sources a young civilization might find on its home world—the list is limited by physics: combustion, solar, wind, geothermal, tides, nuclear, and a few others. Even though our initial models were simple, they still revealed a radical truth about the challenge we face as we push the Earth into its human-dominated era. Unless the universe is deeply biased against it, there have been other civilizations across space and time that faced these challenges. Anthropocenes may be common.
As I explore in my new book, Light of the Stars: Alien Worlds and the Fate of the Earth, our dawning realization that we are profoundly shaping Earth’s future provides us with the impetus to stop acting like cosmic teenagers with power but little wisdom. From that perspective the true narrative of climate change isn’t some small, local drama of Democrats vs. Republications or business interests vs. environmentalists. Instead, it’s a cosmic test, one that gives us a chance to join those who successfully crossed this burning frontier—or the chance to be consigned to the scrap heap of civilizations too shortsighted to take care of their own planet.
Reblogged this on Exposing the Big Game.
Reblogged this on The Secular Jurist and commented:
This is a fascinating article which I recommend reading. The modeling begins with hypothetical planets having technological civilizations which become overpopulated through the exploitation of natural resources. This eventually stresses the ecological balance of the environment sufficiently to trigger a depopulation event. The civilizations which continued to use high-impact energy sources (e.g. fossil fuels) went extinct. Some of the civilizations which switched to low-impact energy sources (e.g. solar power) survived while others also went extinct.
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Reblogged this on SUBURBAN TRACKS and commented:
An interesting lecture for the weekend with astonishing perspectives and visions.
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