Climate change killed the aliens and will kill us too: a case study in GIGO

Ever wondered why we haven’t met any aliens yet? Live Science Senior Editor Brandon Specktor thinks he knows the answer: technologically induced climate change (caused by excessive energy use) may have killed them all off, and it’ll kill us off too, if we don’t get our act together real fast and switch to sustainable sources of energy. In an eye-catching article titled, Climate Change Killed the Aliens, and It Will Probably Kill Us Too, New Simulation Suggests (Live Science, June 6, 2018), Specktor breathlessly reports on the findings of a new study by Adam Frank et al., titled, The Anthropocene Generalized: Evolution of Exo-Civilizations and Their Planetary Feedback (Astrobiology, Vol. 18. No. 5, published online May 1, 2018, Dr. Adam Frank is Professor of Physics and Astronomy at the University of Rochester, New York.

Spektor’s summary of the study’s findings is sobering:

The results, as you might expect, were generally pretty grim. Of four common “trajectories” for energy-intense civilizations, three ended in apocalypse. The fourth scenario — a path that involved converting the whole alien society to sustainable sources of energy — worked only when civilizations recognized the damage they were doing to the planet, and acted in the right away.

“The last scenario is the most frightening,” [leading study author Adam] Frank said. “Even if you did the right thing, if you waited too long, you could still have your population collapse.”

But a model is only as good as the foundation upon which it is built. And it turns out that Frank’s model is built on a foundation of sand.

Easter Island myths

Easter Island statues, known as moai.
Easter Island statues, known as moai. These are the fifteen standing moai of Ahu Tongariki. Image courtesy of Bjørn Christian Tørrissen and Wikipedia.

So where does Frank begin? Specktor reports:

For Frank, the path to modeling an apocalypse starts with Easter Island.

“Easter Island presents a particularly useful example for our own purposes since it is often taken as a lesson for global sustainability,” Frank and his colleagues wrote in the paper. “Many studies indicate that Easter Island’s inhabitants depleted their resources, leading to starvation and termination of the island’s civilization.”

However, the scientific paper by Frank et al. is a little more circumspect than Specktor’s report, acknowledging in passing that the narrative they put forward about the demise of Easter Island’s civilization is a controversial one:

Easter Island is surrounded by more than 1000 miles of ocean in all directions. As described by Basener and Ross (2005), the island was colonized between 400 and 700 AD by a small group of at most 150 humans. Sometime between 1200 and 1500 AD, the population grew to approximately 10,000, and the inhabitants built a culture that was artistically and technologically sophisticated enough to construct and transport their iconic stone statues. While there remains debate about the details of its history, many studies indicate that Easter Island’s inhabitants depleted their resources, leading to starvation and termination of the island’s civilization (Reuveny, 2012; Rull, 2016).

The only trouble with this narrative is that it’s one-sided, out-of-date and quite likely wrong. Even the date of colonization is contentious, with more recent studies (see also here) favoring a date of 1200 A.D. rather than an earlier date of 400 to 700 A.D. The date matters, because if it’s wrong, the rest of the narrative collapses like a house of cards.

Digital recreation of the ancient landscape.
Rapa Nui: a digital recreation of its ancient landscape, with tropical forest and palm trees. Image courtesy of Rod6807 and Wikipedia.

Catrine Jarman, a PhD researcher in Archaeology and Anthropology at the University of Bristol, is the leading author of a recent study titled, Diet of the prehistoric population of Rapa Nui (Easter Island, Chile) shows environmental adaptation and resilience (American Journal of Physical Anthropology, 30 June 2017, Her research findings are summarized in an online article titled, The truth about Easter Island: a sustainable society has been falsely blamed for its own demise (The Conversation, October 13, 2017):

Recently, Rapa Nui [Easter Island] has become the ultimate parable for humankind’s selfishness; a moral tale of the dangers of environmental destruction. In the “ecocide” hypothesis popularised by the geographer Jared Diamond, Rapa Nui is used as a demonstration of how society is doomed to collapse if we do not sit up and take note…

The ‘ecocide’ narrative doesn’t stand up

The ecocide hypothesis centres on two major claims. First, that the island’s population was reduced from several tens of thousands in its heyday, to a diminutive 1,500-3,000 when Europeans first arrived in the early 18th century.

Second, that the palm trees that once covered the island were callously cut down by the Rapa Nui population to move statues. With no trees to anchor the soil, fertile land eroded away resulting in poor crop yields, while a lack of wood meant islanders couldn’t build canoes to access fish or move statues. This led to internecine warfare and, ultimately, cannibalism.

Concerning the first claim, Jarman points out that the island’s population was never terribly high to begin with: “Most archaeologists agree on estimates somewhere between 4,000 and 9,000 people.” More significantly, “there is no real evidence of a population decline prior to the first European contact in 1722.” What’s more, the obsidian flakes or “mata’a” littering the island, which had previously been interpreted by some archaeologists as fragments of weapons used in warfare, turn out to have been “domestic tools or implements used for ritual tasks.” (See here, here and here for further details.) As if that were not damaging enough for the “warfare” thesis, a mere 2.5% of human remains from the island display evidence of injury, and most of them show signs of healing – in other words, the injuries weren’t fatal ones, as they would have been in warfare. Finally, there’s no hard evidence of cannibalism.

And what of the claim that the palm trees on Easter Island were cut down by the local inhabitants, in a savage and ecologically short-sighted act of deforestation? Instead, Jarman thinks it is more likely that a colony of rats, which arrived on the island at the same time as the earliest Polynesian colonizers, slowly eliminated the palm trees by eating the seeds and saplings. In any case, there would have been no need to chop down the trees on the island, in order to move the statues. Scientists have demonstrated how three small teams consisting of no more than two dozen people altogether could have easily moved a large statue using ropes, without any need for wooden rollers (see here). Nor was a large population needed to construct the statues in the first place: Lipo [one of the study’s co-authors] and other archaeologists have demonstrated how the statues could have been constructed by a population of just a few hundred people, using clever engineering techniques that were familiar to ancient peoples. And how did those people manage to put 13-ton stone hats on top of the heads of these statues? By using stone and soil ramps. Prehistoric technology is sometimes capable of some amazing feats.

Finally, there’s positive evidence that the islanders knew how to live sustainably, which contradicts the “ecocide” narrative peddled by doom-mongers, according to a recent report by Laura Cole, who also interviewed Jarman (Bones of contention: the truth about Easter Island, Geographical, December 16, 2017):

‘If you look at the chemical signature of the [islanders’] remains, it becomes clear that this was a population that knew how to manipulate the soil and harvest from the sea,’ says Cat Jarman, who has recently published two papers on data she gleaned from ancient islander’s (sic) rib fragments. By studying the collagen in the ribs, Jarman has been able to analyse eating habits, going some way towards clearing their reputation for unsustainability.

‘The information we have found from these remains is inconsistent with the ‘ecocide’ narrative’ says Jarman. ‘For one, the soil on the island is very nutrient poor, but the islanders’ remains show high levels of nitrogen isotopes.’ This suggests that the population was eating crops grown from deliberately fertilised soils – showing that the Rapa Nui had extensive knowledge of how to grow food from hostile environments. The high ratio of carbon isotopes, meanwhile, show that the island’s predecessors were also ample fishermen. Jarman found that around half of their diet was made up of seafood.

Indeed, the Dutch captain Jacob Roggeveen, the first European to arrive on Easter Island in 1722, reported that the people he met on the island had plenty of food, which they shared with him and his crew.

So, what caused the island’s population to subsequently plummet? As Jarman tells it, the blame rests on outside interference – in particular, the slave trade and disease:

Throughout the 19th century, South American slave raids took away as much as half of the native population. By 1877, the Rapanui numbered just 111.

Introduced disease, destruction of property and enforced migration by European traders further decimated the natives and lead to increased conflict among those remaining.

Bad modeling assumptions

Some readers may object that even if the example used by Dr. Frank et al. in their simulation is a bad one, it doesn’t invalidate the study’s mathematical results. Or does it? In their study, Frank et al openly acknowledge their reliance on an earlier model by Basener and Ross (2005), which shaped their thinking:

In the work of Basener and Ross (2005), a model for Easter Island tracked both the population n and a resource r directly related to the island’s human carrying capacity (see also Safuan et al.,2012)…

In this model the resource is renewable and has its own carrying capacity k. In addition, the resource has an additional “death rate” or sink in the form of human consumption governed by the parameter H. This model captured the qualitative rise and fall of Easter Island’s population as it overshot the carrying capacity provided by the island’s resources. While the results of Eq. 3 drive too rapid a collapse of the population to fully fit the data for the explicit case of Easter Island, they do provide us with a starting point for our own attempts to develop models capturing the coupled interaction of a species with its environment.

The authors then go on to develop their own models, building upon the pioneering work of Basener and Ross (2005). Allow me to quote from the Abstract:

The population of Easter Island grew steadily for some time and then suddenly decreased dramatically. This is not the sort of behavior predicted by the usual logistic differential equation model of an isolated population or by the predator-prey model for a population using resources. We present a mathematical model that predicts this type of behavior when the growth rate of the resources, such as food and trees, is less than the rate at which resources are harvested. Our model is expressed mathematically as a system of two first-order differential equations, both of which are generalized logistic equations. Numerical solution of the equations, using realistic parameters, predicts values very close to archaeological observations of Easter Island. We analyze the model by using a coordinate transformation to blow up a singularity at the origin. Our analysis reveals surprisingly rich dynamics including a degenerate Hopf bifurcation.

The authors’ conclusions would be quite impressive, if the archaeological findings on Easter Island actually backed them up. As we’ve seen, they don’t: more recent studies have discredited the “ecocide” narrative, or at the very least, rendered it highly dubious, and as Frank et al. point out in the passage quoted above, the population collapses too rapidly in Basener and Ross’s 2005 model, anyway.

Additionally, the model developed by Basener and Ross is based on a limiting assumption: it applies only in the special case where “the growth rate of the resources, such as food and trees, is less than the rate at which resources are harvested.” Not all of the four scenarios described by Frank et al. in their 2018 study (and handily summarized here) are subject to the limiting assumption of Basener and Ross’s 2005 model. In the second scenario, for instance, “the population recognizes it is having a negative effect on the planet and switches from using high-impact resources, such as oil, to low-impact resources, such as solar energy.”

Nevertheless, Frank et al.‘s 2018 study is blinkered in its outlook, possibly owing to the influence of Basener and Ross’s 2005, which the authors take as their springboard. Central to the simulations carried out in the study by Frank et al. is the notion of an environmentally dependent carrying capacity K(e), which is defined as the product of two factors: K0, the human carrying capacity for an optimum environment, and the term (1 – e/ec), where ecis the critical value of the environment, where the human carrying capacity goes to zero. The authors also assume that e = 0 is the “natural” state for the environment. In other words, even under ideal circumstances, the carrying capacity for the environment can never exceed K0. This, I have to say, is bogus.

Wheat yields in Least Developed Countries
Wheat yields in Least Developed Countries since 1961. Data from Food and Agriculture Organization. Image courtesy of Grendelkhan and Wikipedia.

As a 2013 Thought Piece by AGR Partners, titled, What is the Earth’s Carrying Capacity? points out, “Advances in technology have allowed the planet to support a much larger population than that envisaged by Malthus in the 18th century” (p. 2). In other words, the carrying capacity is not fixed at some “optimum” value K0; it increases as our technology improves. The AGR Thought Piece listed a range of estimates, varying from half a billion up to 14 billion people (pp. 4, 10), but even these estimates are relative to our present technology. In a lively exchange of views on the subject at Quora, some contributors waxed enthusiastic, with one even suggesting a figure of 639 trillion, assuming that we could somehow harness the power of a Dyson sphere, in the future:

A Dyson sphere or swarm, which would capture solar energy currently being dissipated into space, would improve that energy capture by nine orders of magnitude, into the sextillions. In this case, the limiting factor would probably be physical space on Earth itself. Food (which would be volume intensive) could be grown in the low-rent real estate out in low earth orbit, but ground space itself would be very scarce. Assume 1000 m^3 per person for all human activity, and a fairly arbitrary upper limit of 10 km on vertical space for human use, but that 50% of the entire earth’s surface could be put in use (parks could be integrated into the giant megatowers, floating cities, etc). These assumptions produce a maximum of 639 trillion.

The same contributor readily acknowledged that at our technological level, Earth’s carrying capacity is “probably not much higher than 10 to 15 billion,” and he’s almost certainly right. It may even be less than that. But whatever it is, the important point is that Earth’s human carrying capacity cannot be meaningfully defined apart from human technology.

Frank et al. appear to belatedly recognize this point, towards the end of their paper. In section 7 (Discussion and conclusions), they make the following admission, which undermines the predictive power of their model and calls into question the doomsday thinking it engenders:

In our current model, for example, the population’s use of a resource only contributed negatively to the state of the resource. The development of sustainable civilizations may, however, include specific attempts to create/evolve cooperative relationships with the biosphere such that some interactions increase the availability of the resource, for example, by greening the desert to increase food production using technology (Kleidon, 2012).


Concluding thoughts

Let me close with a final observation. Humans are messy creatures, who are always solving some problems at the same time as they create other, new ones. We will never achieve total sustainability, in our lifestyle. Sustainability is possible only where there is stasis. Inevitably, to progress is to upset the Earth’s balance, to some degree. Or as energy guru Vaclac Smil put it in a recent interview: “You ask me, ‘When will the collapse come?’” Smil says. “Constantly we are collapsing. Constantly we are fixing.”

In a recent article titled, A Critical Look at Claims for Green Technologies (IEEE Spectrum, 3 June 2018), Smil demonstrates convincingly that green technologies will take generations to solve our environmental problems. Academic studies which urge us to start panicking about our fragile ecosystems now, before it’s too late, are simply not helpful. What’s more important is to pick a smart solution that actually works, rather than a boondoggle that feels good but accomplishes nothing. (Case in point: Germany’s solar revolution, which hasn’t reduced its dependence on fossil fuels, from which it continues to obtain 80% of its energy.)

What we need to harness, then, is the power of human creativity itself, by building a fully integrated, inter-connected society in which people can continually monitor all parts of the globe, rapidly identify problems affecting the Earth’s ecosystems and then share possible solutions, before deciding on one which is most likely to work and least likely to cause severe, long-term damage. In order for such a society to exist, a certain critical mass of human talent will be required, as people from all fields of expertise will need to be able to freely exchange their ideas about how to solve unforeseen problems. That, in turn, presupposes the existence of a truly global civilization, numbering in the billions at the very least. Why? Because two heads are better than one – and billions of heads are better than millions. Let’s hope that some of those heads find a way for all of us to reduce our collective ecological footprint.


6 thoughts on “Climate change killed the aliens and will kill us too: a case study in GIGO

  1. Wow. All this prompted by a paper on aliens.!
    I have read also that easter iSland did not decline from the usual story of human war and food loss.
    Probably the statues was a fad, like everywhere else in mankind, and then the people rejected them. Like disco!
    There were lots of people there when it was discovered.
    who pays these professers/science writers to make papers etc for the public based on caluculations about alien worlds surviving/dying??
    If they can do that probability math then they could do a idea like MUTATIONS and how they would, by same math, create this or that!! oh wait they do do that!!

  2. The only trouble with this narrative is that it’s one-sided, out-of-date and quite likely wrong.

    You are such a stickler! X>{

  3. Robert Byers: Probably the statues was a fad, like everywhere else in mankind, and then the people rejected them. Like disco!

    If someone, other than Robert Byers, could provide a reasonable theory why aliens rejected disco, then, and only then, I will be willing to be persuaded that aliens were exterminated by some kind of a climate change…
    I’m personally more prone to believe that the obvious lack of boogie-boogie and due to that likely jiggy-jiggy, did the trick 😉

    Anybody with me?

  4. I do think we have a problem.

    As you seem to at least hint, the biggest problem is not with our use of fossil fuels. The really big problem is our insistence on continued economic growth. And that’s a deeply ingrained cultural problem.

  5. Neil Rickert:
    I do think we have a problem.

    As you seem to at least hint, the biggest problem is not with our use of fossil fuels.The really big problem is our insistence on continued economic growth.And that’s a deeply ingrained cultural problem.

    I think your brush is too broad for the canvas.
    I strongly doubt that economic growth alone provides any tangible benefit to a majority of the world’s population (at best it is a game of beggar-my-neighbour, and at worst an engine for environmental and social catastrophe).
    Having said that, it clearly is an unavoidable obsession for companies trapped in the self-defeating logic of capitalism – and for the governments that serve their interests.

  6. There are various problems, all a result of excessive consumption, which arises from too many people, but the CO2 one seems to be the worst. The Keeling curve is just scary.


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