I think this is the beginnings of an economy based on perpetual growth and fossil fuel energy running headlong into geological energy constraints. Basically I see an undulatory downward path for the rest of my life. From here out, I think any rallies in our economic condition are going to be met with spiking commodity prices that knock us right back down.
Posted: Sat Feb 09, 2008 7:28 am Post subject: Carrying capacity
I'm starting this thread to really flesh out the issue of Earth's carrying capacity for human population. Feel free to shoot me down as best you can, I hope to learn something.
I should start, probably, by mentioning that I am interested in what is possible, in principle. I don't want to get into predicting the likely near- or long-term future; that's a very different discussion to what I have in mind.
I have heard figures suggesting that post-fossil fuel carrying capacity is far, far less than current population (let's say 1B or less compared to today's 6B+).
This seems very reasonable in isolation and is extremely troublesome, of course, because it seems to imply massive die-off, a subject often discussed here as far as I can see. And rightly so.
However, I'd like to know a bit about where this calculation comes from because I am starting to seriously doubt this way of thinking.
From earlier discussions I gather that Liebig's Law of the Minimum is used in identifying carrying capacity. This seems very logical for a closed system. You might argue that the Earth is a closed system in any practical sense. I want to question that in 2 specific ways which I address below.
The natural question that arises if you try to apply Liebig to Earth's human population is, what is the limiting nutrient?
My argument is that it is of necessity any high-quality (low entropy) energy source.
Because:
1. Suppose that the limiting resource is a chemical compound X.
2. This chemical compound is composed of elements (A, B, C ...). An amount of energy E1 is required to configure these elements into the compound X. (In some cases E might be negative? No matter).
3. Further energies (E2 and E3 respectively) are needed to extract X from the natural surroundings and process it into a consumable form. Or, to extract and process the constituent elements (A, B, C ...).
4. If humanity is faced by a limitation in supply of freely available X, he needs to apply energies E2+E3 or E1+E2+E3 to get it.
5. If any of the elements (A, B, C ...) begin to act as Liebig's limiting nutrient, then what is required is input of energy E4 to create the required nuclear transformations to create them. For heavier elements this is possible by fission, for the lighter fusion might be required (Helium springs to mind ).
6. Thus the limiting factor is always energy.
I think this chain of logic well illustrates why I consider that considering the Earth a closed system is wrong wrt carrying capacity:
A - It is not a closed system in respect to energy, which I think is effectively the limiting nutrient (more accurately, we can think of the rate of energy input to the Earth, which doesn't change, but could be made to change by diverting solar flux).
B - It is *not* a closed system wrt chemical elements, due to the possibility (and actuality) of nuclear reactions.
Now you might find this attempt to write things "formally" rather irksome. OK. But what I'm really trying to get to is that I think carrying capacity is always a function of available energy. Even if, in practice, we have terrible problems with other things right now, and even if the "formal" argument above breaks down in the gap between theory and practice.
Is 6 billion possible as a stable population with solar power? Nuclear fission? Nuclear fusion? I have no idea, but I see nothing in the fundamental science that rules it out.
And to me the deeper point is that there is a pervasive myth of nature as equilibrium. States of climate, population etc. can never be any better than quasi-stable (thinking here about chaotic systems that mathematicians study). So carrying capacity must be a continually moving target, i.e. not C but C(E).
Joined: Aug 03, 2007 Posts: 4401 Location: Boston Suburbs
Posted: Sat Feb 09, 2008 7:57 am Post subject: Re: Carrying capacity
As long as human beings don't evolve into robots, the main limit to growth is environmental. Human beings have a minimum environmental footprint, even if all you do is sit in a coma. So even if we had limitless access to electricity, it wouldn't help us if we turned the planet into a Matrix style cesspool.
So as long as we do not reduce population, there is no permanent solution in a techofix barring some sci-fi breakthrough like warp drive that would let us colonize other worlds.
Joined: Sep 14, 2004 Posts: 6547 Location: Rural Virginia
Posted: Sat Feb 09, 2008 8:40 am Post subject: Re: Carrying capacity
Carry capacity is indeed a moving target. It falls as our damage, especially our irreversible damage, accumulates. Ultimately, it depends less on fossil-fuel resources (which are a one-shot deal anyway) and more on natural ecosystems. Global warming will also have a lot to say about carrying capacity; as I see it, it will produce a net loss in carry capacity.
Carrying capacity can only be guessed at; the only certainty is that it's far below the current 6.6 billion or so population.
My own guess, at the current state of ecodamage, is 2 billion. But everyone would have to start acting rationally right away. Since that won't happen, the final stable population is likely to be much lower, say a few hundreds of millions. _________________ "Actually, humans died out long ago."
---Abused, abandoned hunting dog
"Things have entered a stage where the only change that is possible is for things to get worse."
---Me and my brother
Posted: Sat Feb 09, 2008 8:49 am Post subject: Re: Carrying capacity
You've both contended (quite reasonably) that carrying capacity is a function of environmental/ecological factors.
However, you need to be much more specific. In the context of Liebig's law, you have to specify what the limiting factor or "nutrient" is.
If it's not a chemical compound, but something like potable water, I'd say that it is not at all difficult to argue that energy can, in principle, overcome that problem, via engineering.
Feel free to argue along another line but you have to be specific about which environmental or ecological factor limits human population to much less than 6 billion.
Joined: Apr 28, 2005 Posts: 3879 Location: West shore Lake Eire, MI, USA
Posted: Sat Feb 09, 2008 8:56 am Post subject: Re: Carrying capacity
ekaggata wrote:
You've both contended (quite reasonably) that carrying capacity is a function of environmental/ecological factors.
However, you need to be much more specific. In the context of Liebig's law, you have to specify what the limiting factor or "nutrient" is.
If it's not a chemical compound, but something like potable water, I'd say that it is not at all difficult to argue that energy can, in principle, overcome that problem, via engineering.
Feel free to argue along another line but you have to be specific about which environmental or ecological factor limits human population to much less than 6 billion.
Ultimately with unlimited energy one can synthesize anything one needs from the raw materials. The only thing you have to have is an abillity to reject waste heat, you can in theory recycle the waste chemicals forever.
Of course this might involve putting a shade in Earth Orbit to offset sunlight _________________ Always appeal to a man's enlightened self interest, you can trust him to look out for himself honestly, It's when you appeal to his Honor or the Common Good that he stops paying attention.
Posted: Sat Feb 09, 2008 10:01 am Post subject: Re: Carrying capacity
I agree that if we had unlimited energy we could engineer our way out of any limiting problem.
- if it is water, we could purify sea water with enough energy
- if it is pollution, we could clean it up with enough energy
- if it is food, we could build scy scrapers with farms on every level (or other fancy farming schemes)
The problem is that for all practical purposes we currently do *not* have access to unlimited amounts of energy. We might in the future, if we survive peak oil and peak energy.
So the fact that energy is the limiting "nutrient" is really bad, because it means that now all other possible limiting factors matter (like water, pollution, food etc).
Joined: Oct 04, 2004 Posts: 5664 Location: Body in OK, Heart in TX
Posted: Sat Feb 09, 2008 10:14 am Post subject: Re: Carrying capacity
ekaggata wrote:
States of climate, population etc. can never be any better than quasi-stable (thinking here about chaotic systems that mathematicians study). So carrying capacity must be a continually moving target, i.e. not C but C(E).
I think your argument about energy being potentially able to substitute for or increase any other limiting factor is an interesting one. However, it seems to me that the earth is an incredibly complex system, both biologically and geologically. Therefore we will never be able (and here is where some might dispute me) to understand all the variables well enough to model it adequately to avoid setting off feedback loops that will kill us when we attempt to engineer a larger human carrying capacity, even given a larger supply of high quality energy. Precisely because it is a chaotic system, as you pointed out above. I agree carrying capacity is dynamic, but within certain bounds. These bounds are probably incalculable with any precision, but just the fact that there seems to be plastic garbage everywhere I look, and a sea of plastic bigger than the United States out in the Pacific, suggests to me that we're already well above whatever limit exists for carrying capacity.
Edit: The concept of diminishing returns with increasing complexity with respect to engineering is another aspect to consider. _________________ "Every junkie's like a setting sun..." - Neil Young
Last edited by Shannymara on Sat Feb 09, 2008 10:17 am; edited 1 time in total
Posted: Sat Feb 09, 2008 10:15 am Post subject: Re: Carrying capacity
Quote:
However, you need to be much more specific. In the context of Liebig's law, you have to specify what the limiting factor or "nutrient" is.
If it's not a chemical compound, but something like potable water, I'd say that it is not at all difficult to argue that energy can, in principle, overcome that problem, via engineering.
It is precisely this sort of thing that makes these kinds of arguments worthless. The Earth's systems do not work in isolation. They never have and they never will. The environment is a great big holistic beast - everything in it lives in symbiosis and synergy. Isolating one particular element means you lose the big picture; and of course, it is the big picture that is most important.
Take your agrument of potable water above - solved with engineering. Great! That's the potable water solved, but where did you get the engineers, rock, cement, tools, pipes, manpower and energy to create the dams, pumps, aquaducts etc? Those things ALL have to be taken into consideration - if even one of them is in short supply, the whole project is scuppered. So you have no potable water even though there is plenty on the planet. Why not just move your humans close to a source of potable water, keep the population down to a level that can be sustained without the need for outside inputs and, for the love of all that is holy, don't muddy up the water to make it undrinkable.
The most basic solution to ANY of your shortages is population reduction to sustainable leves - that goes right across the spectrum of life, from humans to plants to the most humble of bacteria.
Don't build cities in deserts if the inhabitants are dependant on water for life (and aren't we all?) - find a better location to make survival easier. _________________ We've tried nothin' and we're all out of ideas.
I am only one. I can only do what one can do. But what one can do, I will do. -- John Seymour.
Posted: Sat Feb 09, 2008 10:22 am Post subject: Re: Carrying capacity
korosten wrote:
I agree that if we had unlimited energy we could engineer our way out of any limiting problem.
- if it is water, we could purify sea water with enough energy
- if it is pollution, we could clean it up with enough energy
- if it is food, we could build scy scrapers with farms on every level (or other fancy farming schemes)
The problem is that for all practical purposes we currently do *not* have access to unlimited amounts of energy. We might in the future, if we survive peak oil and peak energy.
So the fact that energy is the limiting "nutrient" is really bad, because it means that now all other possible limiting factors matter (like water, pollution, food etc).
Chantal
Chantal,
I'm glad you made this point, not because I agree with you, but because this is another angle that has to be addressed.
My argument was more directed at those who consider that there is a hard limit to population which has already been crossed.
In response to your post, I'd say that if you parse the numbers on solar power and fission power availability, you'll see that there are enormous amounts of energy theoretically available - from incident solar radiation (we're using a tiny fraction of a percent currently), from Uranium (especially via reprocessing+breeding), and from Thorium (far more abundant than Uranium, with further breeding possible).
Not that any single energy source is unlimited (tho' fusion comes as close as to make the distinction meaningless, if we ever make it workable engineering-wise), but the amount of energy available, at least from these sources, not to mention geothermal etc., is absolutely vast by present day standards.
What I'm saying might not seem likely according to what you've seen/read/heard, depending on your sources, but I encourage you to look for example at the extensive threads on fission in this forum.
(Fission is my speciality because I'm a Nuc Eng by training, but the case for solar on this is very strong too, in a different way).
Posted: Sat Feb 09, 2008 10:27 am Post subject: Re: Carrying capacity
Well, when discussing carrying capacity one needs to answer first what is being carried. There are 1.3 billion cattle on this planet, each one requires many times more food than a human. So if a die-off is necessary then we have legally killable mouths.
But, again, what is the limiting factor? You say it is energy, which is reasonable. Our current farm output is not being impacted by pollution, global warming produces a longer growing season, and fertillizer and chemicals will still be readily available because fossil fuels do not run out over night but falls away over a century.
And due to the cost fraction of food versus gasoline, farms and resource extractors will easily outbid individuals for what energy supplies are available. So even if an energy starved die off is necessary, it will not be for at least a century until oil production (conventional and unconventional) is a tiny fraction of today's production and we have finished killing off all other competitors for human energy supplies (cattle, industry, suburbs, etc).
This is, of course, assuming no new energy supplies develop in the 21st century, which is unlikely, since the earth is not a closed system and all the energy we need is readily available from sunlight, either harvested directly (voltaics) or biologically (biofuels).
Posted: Sat Feb 09, 2008 10:33 am Post subject: Re: Carrying capacity
Shannymara wrote:
ekaggata wrote:
States of climate, population etc. can never be any better than quasi-stable (thinking here about chaotic systems that mathematicians study). So carrying capacity must be a continually moving target, i.e. not C but C(E).
I think your argument about energy being potentially able to substitute for or increase any other limiting factor is an interesting one. However, it seems to me that the earth is an incredibly complex system, both biologically and geologically. Therefore we will never be able (and here is where some might dispute me) to understand all the variables well enough to model it adequately to avoid setting off feedback loops that will kill us when we attempt to engineer a larger human carrying capacity, even given a larger supply of high quality energy. Precisely because it is a chaotic system, as you pointed out above. I agree carrying capacity is dynamic, but within certain bounds. These bounds are probably incalculable with any precision, but just the fact that there seems to be plastic garbage everywhere I look, and a sea of plastic bigger than the United States out in the Pacific, suggests to me that we're already well above whatever limit exists for carrying capacity.
Edit: The concept of diminishing returns with increasing complexity with respect to engineering is another aspect to consider.
Interesting. I think you're edging towards what I see as the main challenge to my approach - complexity.
Now I am not trained in any biological field (and poorly educated in it, at that), but as I understand it the concept "biodiversity" is used in some way to encompass this.
Is there some fundamental way in which loss of biodiversity removes our possibility to maintain population? Or is this just a practical heuristic, in which case it might not always apply?
My tendency is to think of biodiversity as just being about system complexity, somehow this is connected to entropy too but it's muddled in my brain.
I've got a picture in my head now of C(E) as a function on a graph, C on the y-axis, E on the x-axis, and it seems like you're saying that C would have a horizontal asymptote somewhere - initial increases in E boost the C dramatically, but as we increase and increase E, some complexity factor (too much complexity in engineering, too little complexity in the biosphere ...?) creates this "diminishing returns".
Have any scientists (perhaps ecologists) looked at this?
If this is what you meant when you talked about capacity being "dynamic but within certain bounds"? Because what I'm looking for is a fundamental reason for any such bound - I don't see it yet, certainly not clearly.
Joined: Oct 04, 2004 Posts: 5664 Location: Body in OK, Heart in TX
Posted: Sat Feb 09, 2008 10:54 am Post subject: Re: Carrying capacity
ekaggata wrote:
Is there some fundamental way in which loss of biodiversity removes our possibility to maintain population?
If this is what you meant when you talked about capacity being "dynamic but within certain bounds"? Because what I'm looking for is a fundamental reason for any such bound - I don't see it yet, certainly not clearly.
Well, I'm sure this is an oversimplification, and my background is also in physical sciences rather than biological so I'm not an expert either, but the way I think of the importance of biodiversity is that a web is more resilient than a chain. In a chain, one broken link means the whole thing is no longer functional. In a web, you can break a few strands and still have it function effectively - up to a point. This is why I disagree with JohnDenver when he says the extinction of bacteria and insects isn't a big deal. We don't know the implications. And these simpler life forms, phytoplankton for example, are the foundation of a pyramid on which life depends.
As for the bounds, taken to extreme we could say there's a finite amount of mass on/in earth. If you're restricting the discussion to earth rather than assuming we start colonizing space, I'd say that imposes a hard limit.
But what I tried to convey in my previous post with respect to bounds was that I do not believe we have, or ever will have, the ability to understand the earth's biological and geological systems well enough to control them to the level required to use infinite energy to increase carrying capacity infinitely. The atmosphere is a fairly simple system compared to the biosphere, for example, and we can't even model the weather very well.
The complexity and technology we've achieved via industrialization has a lot of people deluded into thinking there are no limits, IMO. But we do have limits, both physical and intellectual. IF we had no intellectual limits and could model the earth (and/or other similarly complex systems) accurately, and IF we had infinite high quality energy to work with, then I agree it's theoretically possible we could increase carrying capacity by many orders of magnitude.
I'm ignoring the (equally important IMO, if not more so) spiritual and moral/ethical aspects of the implications of this discussion for the sake of staying on topic, by the way. _________________ "Every junkie's like a setting sun..." - Neil Young
This group is generally trying to say what our carrying capacity is using simple methods and not relying on fossil fuels.
They say we are 23% over what we can regenerate so that would put our carrying capacity at about 4.5 to 5 billion.
Now that presumes, I think, a maximum number of people. Not a maximum quality of life and working at near 100% efficiency.
So this is a Maximum Population carrying capacity.
If on the other hand, you want all people to have a higher standard of living then you need to have fewer people. We in the West experience a very energy dense life style. We burn something like 10 times the calories of the "minimum." So extrapolating and assuming some technological advances and living a more modest life style lets say we can get by using half the energy we use now, which is still 5 times the energy of the Minimum.
That math quickly leads us to a carrying capacity of 1 billion if we are to lead a life we are accustomed to.
Obviously overly simplified but probably as good a ball park figure as you will get with reasonable input. May be 500 million, may be 2 billion, thats all within the range.
Of course you are likely to NOT have everyone living at the same level then you would have a mixture, as you do today. A few rich energy hogs and many poor slobs slaving away on starvation diets to feed the masters. My guess is about...........3 billion. Lots of environmental damage, not a high quality of life. Very little nature to enjoy short of deserts.
Warning: These are optimistic numbers assuming that the earth retains the current ability to support biomass. Environmental damage could seriously degrade these numbers. The chance that technology will improve the numbers is, IMO, very, very, low.
Joined: Nov 15, 2007 Posts: 339 Location: US East Coast
Posted: Sat Feb 09, 2008 1:43 pm Post subject: Re: Carrying capacity
LoneSnark wrote:
Well, when discussing carrying capacity one needs to answer first what is being carried. There are 1.3 billion cattle on this planet, each one requires many times more food than a human. So if a die-off is necessary then we have legally killable mouths.
But, again, what is the limiting factor? You say it is energy, which is reasonable. Our current farm output is not being impacted by pollution, global warming produces a longer growing season, and fertillizer and chemicals will still be readily available because fossil fuels do not run out over night but falls away over a century.
And due to the cost fraction of food versus gasoline, farms and resource extractors will easily outbid individuals for what energy supplies are available. So even if an energy starved die off is necessary, it will not be for at least a century until oil production (conventional and unconventional) is a tiny fraction of today's production and we have finished killing off all other competitors for human energy supplies (cattle, industry, suburbs, etc).
This is, of course, assuming no new energy supplies develop in the 21st century, which is unlikely, since the earth is not a closed system and all the energy we need is readily available from sunlight, either harvested directly (voltaics) or biologically (biofuels).
Lone,
Just wanted to say that I agree with this post, all this will take time, perhaps even centuries. We may run through a couple of cycles where we drop pretty low and them over build and then drop off again before we settle onto a stable population, if we ever do.
Posted: Tue Feb 12, 2008 4:07 pm Post subject: Re: Carrying capacity
How much energy does it take to revive a species that we have driven to extinction?
Or to rebuild an entire ecosystem full of species interacting in ways that have taken millions of years to evolve together?
How much energy does it take to bring a dead ocean back to life?
What works for mechanical systems does not work so well for living systems. They are qualitatively different entities.
There is one species of fungi that fills a crucial stage in turning rotting matter into useful soil that plants will grow in. If we manage to drive it to extinction, as we are doing to hundreds of species every day, a large part of the world will become sterile.
Snark is being his usual sunshiny self in hoping that GW will mainly lead to longer growing seasons, bless his merry soul;-). I hope he's right, but I am dubious, and I'm not alone.
There are vast unknowns and uncertainties here, but most climatologists are not so sanguine. GW is sure to lead to more extremes--both too much rain and too little, as we are starting to see around the world. Yes, the Sahara will likely get more rain and the tundra will warm, but neither of these have soils that are likely to me of much use for a long, long time.
The main thing is GW is driving the planet well out of climatic norms of the last 10,000 years (Holocene) during which agriculture developed. The idea that this new climatic system will be better suited to agriculture than the climate in which agriculture was developed is...optimistic, to put it charitably.
Healthy soil, I would say, is one very important limiting factor. And we are losing healthy soil very quickly. Remember that healthy soil includes enormous numbers and diversity of bacteria and other micro-organisms, the interactions of which we are far from understanding. Such living soil is not easily replaceable with energy, and more than an ecosystem is.
With all the energy in the universe, we cannot recreate creation. However much we want to think we are, we are not God or gods, or what ever you want to call the billions of years that brought about the breathtaking and beautifully diverse world we inherited and are destroying.
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