Scientists recently modeled a range of interactions between energy-intensive civilizations and their planets. The results were sobering.
We’re interested in how exo-civilizations develop on their planets. Given that more than 10 billion trillion planets likely exist in the cosmos, unless nature is perversely biased against civilizations like ours, we’re not the first one to appear. That means each exo-civilization that evolved from its planet’s biosphere had a history: a story of emergence, rising capacities, and then maybe a slow fade or rapid collapse. And just as most species that have ever lived on Earth are now extinct, so too most civilizations that emerged (if they emerged) may have long since ended. So we’re exploring what may have happened to others to gain insights into what might happen to us.
We used population biology tools to build a simple model for the evolution of a civilization with its planet. In our approach, the exo-civilization’s population and the planetary environment are braided together by energy use and its consequences. The planet gives the civilization energy resources. The civilization consumes them to do the work of civilization building. As a civilization harvests more power from the planet, its capacities soar. That includes the ability to make and feed more babies. This link between available energy (in the form of food for simple organisms) and rising birth rates is fundamental to population biology.
And for human civilization the steep rise we’ve seen in population is closely tied to fertilizer involving fossil-fuel use. So greater energy will, in the beginning, mean bigger populations. But there’s no free lunch from a planetary perspective. Using all that energy has to result in feedback on the planet. That’s what we earthlings are just starting to see with climate change.
If global warming gets really nasty, everything from energy harvesting to food production is going to get severely stressed and our large human population won’t be sustainable. That’s why our exo-civilization models linked rising planetary impacts with population declines. It was all pretty straightforward, requiring no assumptions about alien economics, sociology, or any other science-fiction ideas.
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.” ... 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.
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Frank A., Carroll-Nellenback Jonathan, Alberti M., and Kleidon A. The Anthropocene Generalized: Evolution of Exo-Civilizations and Their Planetary Feedback Astrobiology May 2018.... We find four distinct classes of trajectories in our models.
- Sustainability: For these classes, stable equilibria (n*, e*) exist which can be approached monotonically. The population rises smoothly to a steady-state value. The planetary environment is monotonically perturbed from its initial value e0 and reaches a new steady state that can support a large population.
- Die-off: For these classes, stable equilibria (n*, e*) exist which cannot be approached monotonically. The population overshoots the environment's carrying capacity, reaches a peak, and is forced to decline as the environment reaches its new steady state.
- Collapse: For these classes, stable equilibria with nonzero population do not exist. In these cases the population experiences a rapid decline after reaching its peak value. It is noteworthy that collapse can occur even though the population has begun leveling off due to the civilization's switching from high-impact to low-impact energy modalities.
- Oscillation: In this class, a stable limit cycle exists rather than an equilibrium. The population and the planetary environment cycle between high and low values.
A Critical Look at Claims for Green Technologies
... Claims of impending innovation may be seen (although they are not labeled as such) as being largely aspirational—but the benefits would be great if even just a fraction of their goals were realized during the next generation.
At the same time, these claims should be appraised with unflinching realism.
... Human beings have always sought innovation. The more recent phenomenon is this willingness to suspend disbelief. Credit this change to the effect that the electronics revolution has had on our perceptions of what is possible. Since the 1960s, there has been an extraordinarily rapid growth in the number of electronic components that we can fit onto a microchip. That growth, known as Moore’s Law, has led us to expect exponential improvements in other fields.
However, our civilization continues to depend on activities that require large flows of energy and materials, and alternatives to these requirements can’t be commercialized at rates that double every couple of years. Our modern societies are underpinned by countless industrial processes that have not changed fundamentally in two or even three generations. These include the way we generate most of our electricity, the way we smelt primary iron and aluminum, the way we grow staple foods and feed crops, the way we raise and slaughter animals, the way we excavate sand and make cement, the way we fly, and the way we transport cargo.
Some of these processes may well see some relatively fast changes in decades ahead, but they will not follow microchip-like exponential rates of improvement.Our world of nearly 8 billion people produces an economic output surpassing US $100 trillion. To keep that mighty engine running takes some 18 terawatts of primary energy and, per year, some 60 billion metric tons of materials, 2.6 billion metric tons of grain, and about 300 million metric tons of meat.
Any alternatives that could be deployed at such scales would require decades to diffuse through the world economy even if they were already perfectly proved, affordable, and ready for mass adoption.
... Vertical farms in cities can produce—profitably—hydroponically grown leafy greens, tomatoes, peppers, cucumbers, and herbs, all with far less water than conventional agriculture requires. But the produce contains merely a trace of carbohydrates and hardly any protein or fat. So they cannot feed cities, especially not megacities of more than 10 million people. For that we need vast areas of cropland planted with grains, legumes, and root, sugar, and oil crops, the produce of which is to be eaten directly or fed to animals that produce meat, milk, and eggs. The world now plants such crops in 16 million square kilometers—nearly the size of South America—and more than half of the human population now lives in cities.
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