Monday, December 22, 2008

The Earth's Carrying Capacity

It turns out Warren Buffett is interested in the earth's capacity to sustain us. On page 642 of the new biography, The Snowball, he holds forth on the subject to author Alice Schroeder:
There is a carrying capacity to the earth. It's far, far, far, far greater than [Thomas] Malthus ever dreamed. On the other hand, there is some carrying capacity, and the thing about carrying capacity is that you want to err on the low side. If you were provisioning a huge rocket ship to the moon and had enough for two hundred people and didn't know how long the journey would take, you probably wouldn't put more than a hundred fifty people on the ship. And we have a spaceship of sorts, and we don't know how much the provisions are good for. It's very hard to argue that the earth would be better off in terms of average happiness or livelihood with twelve billion people instead of six.
Buffett is right that Malthus' original estimates of the maximum human population were way off. But that doesn't mean the limits are meaningless, and Buffett argues that we should plan for a margin of safety in calculating the effect of population growth, just as he does when making investments.
The earth's population is expected to reach 9 billion by the middle of this century, and gradually slow its growth. A country's population tends to grow more slowly and stabilize as education and living standards improve. Earth watchers like Lester Brown expect the earth's population to stabilize eventually, either through social restraints or, as he wrote in Beyond Malthus, "because nature ruthlessly imposes its own restraints."
The earth's capacity to sustain human life depends as much on technology as it does on sheer numbers. It is also worth pointing out that markets and populations start to behave erratically when their limits are reached, whether those limits are fuel, food, land or water.
The fabled Green Revolution greatly improved crop yields. Equally dramatic changes in energy technology will be needed to reduce carbon emissions and maintain our ability to feed our growing numbers. It's hard to cultivate land that's under water. And Brown points out that reliable water sources from mountain ranges like the Rockies or the Himalayas will be affected as snow accumulation is reduced by global warming.


Blogger Mikata Karasu said...

Global population is nearing 7 billion. I think it's pretty clear that we’ve already exceeded global carrying capacity. We are now in “overshoot”.

Different theorists using different methods seem to end up agreeing that global carrying capacity is probably about 2 billion. (This assumes some level of social justice and a moderate, low by US standards, standard of living. More is possible if you accept a cattle car / Matrix-esque "life".)

In any case, we will get to that much-lower-than-7-billion number the hard way (wars, famine, disease, and their accompanying losses of environmental quality, freedom, and social justice) OR the less hard way (immediately and drastically reducing our population voluntarily). And yes, this would have to be all of us, and yes, everywhere. There is no scenario in which population growth is a "good thing" long term.

Yes a drop in population would cause problems, but none of those problems are as big as the problems, suffering, and environmental collapse that is certain to occur if we don’t.

It’s too late for any “us” vs “them” arguments or any belief that national boundaries will do much to help anyone in the long run. This is a global issue with local and nation-state consequences. For example, immigration is a consequence of overpopulation, not a cause of it. Likewise, global climate change is not impressed by national boundaries.

I disagree with the argument that there is some “right to reproduce” that must be accommodated in this scenario. If there is any "right to reproduce" it's in the concept that one has the freedom to nurture a child or children and form some sort of family. Biological reproduction is not necessary to do that and there are many in need of this sort of nurturing.

I would also argue that at least one criterion to reproduce would be to not only have the necessary skills and resources to parent a child for 18 years or so, but that doing so would not cause suffering for others either now or in the future.

One interesting logic trail in all this is that if we are truly beyond our global carrying capacity (and it seems clear we are) no one can biologically reproduce and truly meet that criteria, since each added child now assures more people suffer later.

One of the key factors in this scenario is also our sense of time. This is a slow motion crash that requires both immediate and consistent long term action, a bit like trying to steer a supertanker that's on a crash course by putting in consistent input over a multi year time frame, and the one effective input is for all of us everywhere to stop making babies. The supertanker analogy is also apt because it was the "one time gift" of oil that allowed us to get this far out on a limb, and peak oil has already happened.

No technological / "alternative energy" options have the capacity or can be ramped up fast enough to avoid major global calamity. That isn't to say we shouldn't do them. Aggressively shifting to alternative energy is necessary, just not sufficient.

For more comprehensive analysis of all this I suggest

Approaching the Limits

Bruce Sundquist on environmental impact of overpopulation

The Oil Drum Peak Oil Overview - June 2007 (

...and of course the classic "Overshoot" by Catton

Note that I don't think humans are smart enough to deal with this. Nature bats last and assertively.

6:28 PM, December 22, 2008  

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