[Xichekolas]

Population growth has been slowing in the last couple decades. An odd effect of economic success (as a nation) seems to be vastly lower birthrates. It could be ready access to contraceptives, or more women working, or whatever, but it's an obvious trend. Nations like Japan and Italy have negative replacement rates at the moment.

See: http://en.wikipedia.org/wiki/World_population#Rate_of_increa...

Aside from that, population pressures do build, but they can't just build forever. Eventually something happens (war, famine, technological breakthrough) that solves the problem in the short term. If we suddenly run out of some critical resource, that will suck for individuals, and the ensuing resource wars may take a terrible toll, but the race as a whole will survive and grow again.

[nazgulnarsil]

sure, but the point is to choose sustainability because if we don't nature chooses war, famine, or disease for us.

[Xichekolas]

But 'sustainable' population isn't necessarily zero population growth. On a macro scale, even the population explosion of the last 40 years has so far been sustainable due to huge advances in agriculture, health care, and energy. As long as our ability to provide those things grows at the same or better rate as our population, it is sustainable.

(I'll note I am using the literal definition of 'sustainable' here... able to be sustained. As an nerd, I'd really like our future ability to provide those things to be environmentally and socially sound, but that wasn't what I was talking about.)

Exponential population growth becomes a problem when we give up innovating.

[nazgulnarsil]

Of course, but shouldn't we desire that every human has a decent standard of living? we're currently NOT producing/distributing enough for the world's 6 billion humans. people are dying for lack of food and water.

the point is that if we continue to expand at the same rate MORE people will be born into terrible conditions.

It's not so easy to take the stance that technology and free market forces will solve the population problem when you see the horrible results of demand outpacing supply for basic resources in real life. In real life, demand dropping means people died. this isn't an economics class.

[nazgulnarsil]

you mentioned it yourself in another thread: but yes, the growth rate in any given year is limited by resources available and human innovation

I think that human population can well outstrip innovation especially when you consider that an innovation now can take many years to disseminate to the world at large.

[Xichekolas]

But human population hasn't outstripped innovation or our ability to acquire resources up to this point. Why would it now? It's quite evident that worldwide living conditions have generally risen throughout our history. And I don't see why any innovation now would take longer to affect the world at large. If anything, with our superior communication and transportation (compared to the rest of history), innovation propagates much much faster. Hence things like the industrial and the Green Revolution.[1]

Also population growth worldwide has been declining for a couple decades now. Surely our ability to innovate won't likewise decline. Generally innovation seems to accelerate (more people spend more time thinking and less time acquiring basic necessities).

Just read about Norman Borlaug[2] to see what I am talking about. His work on wheat has been credited with saving over a billion people from starvation.

I am curious though, how would you solve the overpopulation problem? Reproductive controls don't work very well (and make people miserable/rebellious), and you can't just kill off a bunch of people (like you said, not an economics class), so what do we do? The most effective birth control method for a nation so far has been economic success for women (look at birth rates in the West compared to the developing world).

[1] http://en.wikipedia.org/wiki/Green_Revolution

[2] http://en.wikipedia.org/wiki/Norman_Borlaug

[nazgulnarsil]

I don't have an answer and I also don't think this problem will ever go away. Humans will always expand right up to the limit of whatever is currently supportable. If we're right at the limit all the time that means fluctuations will sometimes take us above that limit.

[dangoldin]

Jared Diamond has an interesting piece in the NY Times where he discusses consumption factors - the point of it is is that if every single person on Earth consumed at the level of an American, it would be as if the population of the world would be around 70 billion americans. Just something to ponder.

http://www.nytimes.com/2008/01/02/opinion/02diamond.html

[Xichekolas]

But this argument is subject to exactly the fallacy I was talking about. Namely it assumes the following:

1. The increased consumption will happen without a corresponding increase in the ability to provide resources to fuel it.

2. Absolute per capita consumption of scarce resources will remain the same or greater.

3. Everyone on earth will someday have the same level of consumption.

To answer all these:

1. Without an increasing ability to provide resources, consumption levels cannot rise (there would be nothing to consume).

2. As innovation and environmental consciousness progress, absolute per capita consumption of scarce resources will hopefully decrease, in favor of consumption of non-scarce resources. (When we can transmute dirt into energy for instance, or finally have solar-powered transportation.)

3. The upper end will always rise. Someday the entire human race may on average consume at the rate Americans do today, but there will be some group/nation/whatever somewhere that consumes at a much much higher rate still.

---

He is right to argue that we shouldn't just assume everyone in the world could live at Western standards right now with our current ability to procure resources, but it takes a long time to raise living standards, and our ability to procure resources steadily improves as well.

The current consumption rate in Central America probably pales in comparison to America, but would also probably seem really extravagant by US standards circa 1800.

I think the implicit motivation for all this hand-wringing about how much more the West consumes compared to the developing world has to do with some misguided assumption that it is somehow unfair. Equality sounds great in practice, but it'll never be a reality (short of a perfectly altruistic benevolent dictator). Instead of focusing on how unfair it is, why not try and do something to help those at the bottom? Innovate... pull a Dean Kamen and figure out how to cheaply purify water. If his invention works as advertised, he will turn a scarce resource (clean water) into a non-scarce one, which means it can more easily be consumed.

[dangoldin]

I understand both his and yours argument. He's just saying given the current technology/resources, it's not possible to support a world population of 70B.

Clearly they are linked since the world will not move to a 70B population given the resources in the world today - there's just not enough at the moment to support that.

I think one of the points he was trying to make was that when the politicians claim that the goal is to get every country to consume at the same level, it would be challenging, if not impossible, given our current technology.

[Xichekolas]

Yeah, and I totally agree with that point. My problem is that a lot of people seem to hear things like that and mentally translate it to: "everyone needs to consume less or we are screwed".

To me, the better thought would be: "how can we acquire more resources in an environmentally and socially beneficial way?"