I don't have too much time for non-work-related writing nowadays, but I really feel the need to spread this meme. Earlier this week I got into a little dust-up with a hacker-news user called moonchrome over the sustainability of exponential growth. It was in response to a story about the catastrophic fires in Indonesia that are intentionally set in order to clear farmland for oil palms, i.e. the plants from which coconut oil is produced. Oil palms have become a growth industry (no pun intended) since trans-fats have become unfashionable.
During that exchange I suddenly realized that there's probably a whole segment of the population that thinks that overpopulation is not a problem because — space colonization! When earth gets overcrowded, we'll just move to Mars. And besides, those Malthusians have been crying wolf since forever. No matter what happens, technology will save us.
Sorry to be the one to break it to you, but no, it won't, and if you think it will you don't understand the truly awesome destructive power of exponential growth.
There's a classic puzzle that goes like this: imagine you have a jar filled with growth medium and a single bacterium of a species that divides twice an hour. After a week, the jar is full. At what point was it half-full?
The classical answer is: half an hour before the end of the week. But that is wrong. The real answer is that the problem as posed is not possible. A week's worth of unchecked bi-hourly doubling would result in a bacterial population vastly greater than the number of elementary particles in the universe.
It helps only a little that our doubling time at the moment is running about 60 years rather than 30 minutes. That stretches the week out to a few hundred or a few thousand years depending on whether you take the total biomass of earth or the mass of the universe as your limiting factor. Predicting the future is usually a fool's errand, but I hope I don't have to convince you that before we have converted every last carbon atom on earth into a human body, life will get very, very unpleasant.
Even if we manage to colonize Mars, that will only help a little. Imagine that we are able to completely terraform Mars, and produce a biomass more or less equal to that of earth. For starters, colonizing Mars will only help the situation here on earth if we are able to emigrate en masse, which isn't very realistic. But even if we were able to do that, having one more planet only buys us one more doubling time, that is, 60 years at current growth rates, after which we would be right back where we started. And now to get ourselves out of that mess we need two more planets!
OK, say the optimists, so we'll go to the next solar system. No, we won't. Even sending a robot probe to the nearest star is a pipe dream at the moment. The massive emigration required for interstellar colonization to improve the situation here on earth is a pipe dream N times over for some very large value of N. And even if that were not so, as I mentioned earlier, even if you take the total mass of the universe as your limiting factor you only get out to a few thousand years. That's the blink of an eye in the grand scheme of things.
The simple fact of the matter is that exponential growth is necessarily transient. Always. It is not possible to sustain exponential growth in a finite universe. At some point, any instance of exponential growth will cease. The only question is whether it happens because we decide to stop it, or because we discover the hard way what the limiting factor actually turns out to be.
Personally, I hope we do the former, because dealing with the latter will not be fun. But to achieve that we have to change our collective mindset. We have to start thinking about steady-state as the goal rather than exponential growth, because open-ended growth is simply not an option. If we don't control our growth, then sooner or later the laws of physics (and mathematics) will do it for us.
Long before we even consider going to the stars we'll have figured out how to transfer our consciousness to and from some digital state. I suspect that will be the ultimate savior of mankind ... for a very loose definition of mankind.
ReplyDeleteRon: But you've skipped a step. The fact that, mathematically, any exponential process must eventually exceed any finite limit, doesn't at all tell you that humanity on earth is currently in a situation that requires "we have to start thinking about steady-state as the goal", right now. John McCarthy (Stanford AI) spent a lot of time trying to estimate mathematical and physical limits of human population sustainability on earth, and his estimate was 15 billion humans, at "American standards of living".
ReplyDeleteIn any case, you say that current human population growth rates give a doubling every 60 years. That doesn't seem like a particularly accurate way to describe the current situation. The forecast over the next century is actually mostly about change in Africa. The rest of the globe, outside of Africa, doesn't really have a "problem" to "solve".
What are effective methods of creating stable populations? Not through guilt and pleading! But Hans Rosling has an idea. Rosling suggests the (not particularly intuitive) solution: populations have fewer kids, as they get richer. Advanced, wealthy nations (e.g. Japan) are actually having problems of population decline.
Stars My Destination
ReplyDeleteColonizing Mars is a ridiculous idea, only useful for science fiction. Mars can never be suitable for human life. One of the principle reasons for this is that the atmospheric surface pressure is only 0.006 atm, versus 1 atm for Earth. The mass of Mars is insufficient to hold onto an atmosphere like Earths.
Venus is a much better prospect. Venus is similar in size to Earth. Venus has an atmosphere with a surface pressure of 91 atm - but it's probably easier to get rid of atmosphere that it is to add it. Venus, though, is covered by clouds and we therefore don't get many pictures of surface detail. The Soviet Venera probes sent back some limited surface pictures, the last in 1982. Doesn't make good press if you don't have pictures.
Then again . . . the whole idea of colonizing other planets is ridiculous. The expense of colonizing another planet would be better spent cleaning up part of Earth. Much ink has also been wasted on the L5 Society.
We're Doomed
A very depressing book on this topic - limits to growth on Earth - is Overshoot, by William R. Catton, Jr. His thesis is summarized on the cover of the book.
In this book, he calls the belief that technology will aways save us cargoism.
A counter argument to limits is that, well, when humans run out of something, we invent a solution. Running out of farm land? Create farming skyscrapers. This could lead quickly to a cargoism vs. no-it's-not argument.
I expect the worst.
@Don
ReplyDelete> his estimate was 15 billion humans, at "American standards of living".
Sure, but so what? I'm not arguing for any *particular* limit, only that a limit exists, so sooner or later, anti-Malthusian induction will fail no matter how optimistic you are with respect to technological advancement. It's a non-constructive proof. However, we can compute hard upper bounds on when that limit -- whatever it may turn out to be -- will be reached given a growth rate, and when you do the math those hard upper bounds are much (much!) smaller than most people think. So anti-Malthusian induction will eventually lead to catastrophe, and so we should stop accepting it as a valid argument, notwithstanding its predictive power to date.
BTW, I think McCarthy's limit of 15B is not unreasonable, but it is no cause for optimism or complacency. McCarthy was writing in 1995, and his calculations are predicated on a transition to nuclear power, which is not yet underway 20 years later. Furthermore, at current growth rates, we are going to hit 15B before the end of this century, and we may or may not stop there. So we're currently on track to hit or surpass McCarthy's limit within the lifetime of some people currently alive, and *without* the mitigating effects of nuclear power. On that trajectory, climate change poses an existential threat to civilization.
> The rest of the globe, outside of Africa, doesn't really have a "problem" to "solve".
To the contrary, most places on the globe consider population *decline* to be a problem that needs to be solved, and many of those places are trying to "solve" that "problem" through immigration. That is the mindset that needs to change. Sooner or later we will have to figure out how to make economies work in the absence of growth. Either that or face catastrophe. Those are the only two options.
I think we can do it. I just don't think we are doing it.
> populations have fewer kids, as they get richer
Yes, absolutely. That is what gives me hope for the future.
@Publius:
> Venus is a much better prospect
Not really. It's way too hot. The temperature at the surface is hot enough to melt lead, and even "floating cities" (which have been seriously proposed) will have ambient temperatures above the boiling point of water. No one AFAICT has a good story to tell about how to get around that problem.
As we are about to learn the hard way here on earth, it's a lot easier to heat a planet up than to cool one down.
> when humans run out of something, we invent a solution
That is exactly the dangerous attitude that I am arguing against. If we keep growing then we will sooner or later hit a limit that we can't get around with technology. Whether that happens in 100 years or 1000 is TBD. But it won't be 10,000.
Ron: I generally agree with the bulk of your response to me here, so I'll just focus on a few minor remaining disagreements.
ReplyDeleteFirst, many people use "exponential growth overcomes any finite limit!" as a shorthand for "there are already too many humans; current population is already above the planet's sustainable limit." (And thus immediate action is required!) It looks like you carefully distinguished the two cases, but many readers don't.
Re: 15B people. Agreed, but that was at American levels of wealth. The planet can support far more people, living lives of abject poverty, disease, starvation, and death across the deserts, plains, and jungles of Africa. Or, to think of it another way, the bulk of humans living in urban and rural India do not consume anywhere near the kinds of per-capita resources as the average American.
"Sooner or later we will have to figure out how to make economies work in the absence of growth." I don't equate lack of population growth with lack of economic growth. The US has demonstrated roughly a century of 2% productivity growth combined with 1% population growth, for a long-term 3% growth rate in GDP. Cutting that long-term growth from 3% down to 2% (just productivity, no population) doesn't seem like a huge change to the structure of society.
@Don:
ReplyDelete> you carefully distinguished the two cases
Yes, but I still feel a sense of urgency because the system has an awful lot of inertia. By the time it becomes apparent what the hard limit to growth actually is, it will be much too late to do anything about it.
> The US has demonstrated roughly a century of 2% productivity growth
Sure, but that is largely due to picking a lot of low-lying fruit in the form of cheap fossil fuels, easily-obtainable scientific breakthroughs, easily-obtainable efficiency gains, and ignoring externalities like carbon emissions and long-term storage of nuclear waste. It's the same no-brainer: 2% productivity growth is a 35-year doubling time in average income. So in 350 years everyone will be able to afford their own Gulfsteam V. That sounds awesome, except that it isn't actually possible for even 350 million people to each have a Gulfstream V, let alone 15 billion. Somewhere between here and there, something has got to give.
> The planet can support far more people, living lives of abject poverty, disease, starvation, and death across the deserts, plains, and jungles of Africa.
Yes, of course. But I don't consider that a good outcome.
Ron: "a century of 2% productivity growth ... is largely due to picking a lot of low-lying fruit in the form of cheap fossil fuels, easily-obtainable scientific breakthroughs, easily-obtainable efficiency gains, and ignoring externalities"
ReplyDeleteWow! That is a fascinating different claim, essentially independent from your concerns about unsustainable population growth. I have to admit, that I disagree strongly with your perspective. (I would describe it as hindsight bias: you see that what happened, did happen, so you underestimate how difficult or likely it was. Whereas, you can't easily forecast future changes.)
Robin Hanson (overcomingbias.com) would disagree with you. He has an outside-view perspective of world output as a sequence of increasing exponentials, covering animal brains, human foraging, farming, and industry. Long term trends suggest, not that the last century of 2% is unsustainable, but on the contrary that we may be due for a shift to a new, higher, mode of exponential growth.
And what might that mode be? He has a suggestion for that, too: Ems, namely the AI-like (but instead, poorly-understood copies of human brains) uploaded consciousnesses, perhaps living in densely packed virtual worlds of trillions.
I would suggest that might be a worthy topic for you to explore in a post: independent of population trends, what is a long-term forecast for productivity growth?
P.S. The cover of Time magazine this week, is on recent progress in private efforts to build a commercial fusion reactor. Yes, yes, I know that fusion has spent a century being always 30 years away, and perhaps this is no different. But on the other hand we've always known that this is "just" an engineering problem; the physics is simple and uncontroversial. And a human civilization based on fusion would go a whole long way towards taking care of increased energy needs with economic growth, while at the same time dealing with the externalities that you were worried about with our current energy sources.
> That is a fascinating different claim
ReplyDeleteThat's true. (Well, the "different" part anyway. I'm not sure about the fascinating part. :-)
But whether I'm right about that or not is irrelevant. 2% growth cannot continue indefinitely, a few thousand years at most (that's when you run into the limit imposed by the number of sub-atomic particles in the universe), and mostly likely much less than that.
> we may be due for a shift to a new, higher, mode of exponential growth.
Quite possible, but that too must some day come to an end. Sooner or later, we will run out of modes.
> the physics is simple and uncontroversial
That may be, but the engineering is far from simple. It's not even clear that small-scale (i.e. smaller than a star) controlled fusion is even possible.
I'm much more optimistic about solar power than I am about terrestrial fusion. After all, we already have the ultimate fusion reactor humming away next door. It doesn't even need maintenance. We may as well use it.
Ron: Agreed! (With all of it.) Still, I'm excited about a couple more centuries of 2% (or higher!) annual economic growth. That future world should be really interesting. Wish I could stay around to see it.
ReplyDeleteBesides the lithosphere problem...
ReplyDelete> Venus is a much better prospect
Not really. It's way too hot. The temperature at the surface is hot enough to melt lead, and even "floating cities" (which have been seriously proposed) will have ambient temperatures above the boiling point of water. No one AFAICT has a good story to tell about how to get around that problem.
Well, I have a good story on how to cool down Venus. One reason Venus is hot because the surface pressure is 92 atm. So, first step, you have to get rid of 99% of the atmosphere (about 4.75E+20 kg).
Of course, the whole idea of planet engineering like this is ridiculous.
Yes, but I still feel a sense of urgency because the system has an awful lot of inertia. By the time it becomes apparent what the hard limit to growth actually is, it will be much too late to do anything about it.
Do we have any duty to people who aren't even born yet? You're worrying about the lives of people who don't exist.
Pluto
Ok, so you're busy of work - but no mention of New Horizons?
> Do we have any duty to people who aren't even born yet?
ReplyDeleteDuty? I don't know. But...
> You're worrying about the lives of people who don't exist.
Yes, that's a common feature of being a living thing. Genes that make creatures that worry about the survival of future generations tend to reproduce better than those that produce creatures that don't worry about such things.
> no mention of New Horizons
An indication of how busy things are for me these days. The New Horizons photos are awesome!