How Many People does Earth Really NEED?

[Coyote]

Reading the YECs-all-die thread, and thinking about other threads where "the people who believe/do XYZ all vanish", it got me to wondering... how many people does the Earth really truly need, anyway? We have about 6 billion on the planet now...lets supose a general die-off happened, not sudden or dramatic, but just a radical decrease in fertility worldwide.

Let's say that we'd have a generation to adjust, as it became obvious that people were just not replenishing themselves, and that we were able to figure out that it was a natural genetic code or something, heretofore unsuspected, that keeps humanity in check.

In a few generations we can bounce back, meanwhile, across the globe, all nations and regions experience the same rate of population declaine persuant to present percentage levels-- so, like, it's not all taken out on one population group.

How many do we need to meet the following criteria:

Maintain a high level of technology
Maintain high economic standards
Maintain genetic diversity

Of course there'd be a severe economic blow and many corporations that rely on selling vast quantities of goods to vast quantities of people would go under. But once we realized that we could maintain our standards of living, maybe even afford to bring poor nations up because (1) we need to sell something to someone, and (2) now if they live at 1st world standards it won't pollute much because there are fewer of them as well and (3) we need to ensure their survival anyway for genetic diversity.

What's the minimum?

1 billion? 500 million?

[SyntaxVorlon]

Earth doesn't need any of us. If the entire human species just up and vaporized the earth would have an interesting climate for a few thousand years, another ice age maybe, but then it'd go on being filled with life and happy.

For human civilization to be sustained? That would take something entirely different. A billion people could live in a completely automacized first world, running on nuclear power for a few centuries.

[Big Phil]

Earth doesn't need any of us. If the entire human species just up and vaporized the earth would have an interesting climate for a few thousand years, another ice age maybe, but then it'd go on being filled with life and happy.

For human civilization to be sustained? That would take something entirely different. A billion people could live in a completely automacized first world, running on nuclear power for a few centuries.

Would you even need that many? I would think that a technologically advanced population would only need a couple tens of of million (say a country the size of the UK or Germany) to sustain itself, and maybe not even that many.

[SCRawl]

I think that the issue here isn't just survival. After all, I'm sure that a few thousand humans could probably get by, with the survival of the human race in fairly good hands. (One extra cold winter, a nasty virus, or a bad crop one year would be problematic, though.)

No, the issue is continued advancement, standard of living, etc. What level of existence can we hope to have if a large percentage of the population who creates goods (as well as consumes them) suddenly ceased to exist? Could major corporations such as, say, General Motors, continue to operate if there are vastly fewer consumers to purchase their products? Could the rest of this now underpopulated world get by without having General Motors (and their suppliers, and their suppliers' suppliers, and so on) making products for us to consume? It's this whole web of supply and demand, and it relies on making new consumers and producers with each generation.

It's a hell of a question, and I haven't the foggiest notion how to start to answer it.

I suppose that if we wished to design a system, a simple system, for keeping a fairly small population fed, watered, happy, and progressing, we could do it without a lot of trouble. Such a society would not be very diverse, would be slow to change, and slow to react to change, simply because they would lack the over-capacity to implement such changes. Of course, if the means for de-populating the planet is, say, a pandemic, we won't have the luxury of calmly sitting back and pulling the strings.

As for this die-off, it would matter a great deal where all of these people were. If the entire population of, say, Africa suddenly vanished, it would put some serious dents in the world economy, but it would be survivable in the medium term. If Europe or North America suddenly became vacant, then all bets are off. Major corporations all over the world would quickly become extinct, leading to massive unemployment in the West, and then, perhaps governments start to fail. It would be chaos, chaos I tell you.

Yes, this is indeed a good question. I look forward to what the bigger brains have to say, because mine is certainly not up to the task of answering it.

[st. mark]

Being rich is not about having enough. You are not rich until you have a little bit more.

Theoretically less people should give more wealth as there will be more natural resourches pr person. Genetic diversity will suffer, but echonomy and technology I believe could be strong even with suprisingly few people.

However, human psychology and survival instict make it so that most people are never satisfied unless they have more than others. I am materially far richer than most aristocrtas a few centuries ago, but I have no real echonomic power over anyone (not even my wife), so I do not consider myself rich. Maintaining economy is thus not only a matter of material wealth - which may be increased pr. person by fewer to share, but also about power, which will decrease with fewer people around.

[General Brock]

....Huh? What are you planning?

I think at least a billion would be necessary, given the breadth of living cultural and technological knowledge that might need preserving, and the work that would have to be done in some parts of the world to restore or protect the natural envirionment and maintain educational and technological standards. This is assuming a capitalist/secularist economy will still prevail, and everything from fluffy university courses to toxic and nuclear waste sites are properly maintained.

Any less, then wars would also almost certainly be fought as well, as resources are freed from population pressures. A country like Russia or the US would be hard-pressed to maintain geographic integrity in the face of a decline of their domestic populations, since they have extremely populous neighbors whose numbers advantage would only increase with a flat decline in human population.

[kheegster]

I think that if the poorest 1 billion people in the world were to disappear, the world economy wouldn't really feel much of a dent, as they are not major consumers or producers even with their numbers. So that would give a upper limit of 5 billion of a comfortably growing population, I guess...

[Enforcer Talen]

the more, the better. I like having a large resource pool to play with.

my line of thinking is this. with a 1st world economy, you can have 3-5% working on sustainment - primary industries, like mining and farming. then you can have 10-20% in manufacturing, cuz robotics is doing more. then the final 75% is out *discoverign* things. 75% of 1 billion is good - 75% of 10 billion is better.

this assumes, of course, that its a stable environment, no oen is starving, etc.

[Junghalli]

I think a species needs at least a few hundred members to maintain enough genetic diversity to be viable, so that would have to be the absolute lower limit.

[Coyote]

Bear in mind, for those postulating certain population groups disappearing, ie, Africa, the idea is that all the words populations suffer a massive drop in fertility-- so everyone-- first world, developing world, poorest, rogue states, etc, all across the board experience this. So it's not like "all Asians are gone" leavign the rest.

Plus, as a drop in fertility, we have a generation to prepare for this, it's not an "overnight" scenario. For awhile, economies will be hit hard as an elderly population isn't replaced by hordes of youngsters, so we'd have 70 and 80 year old working 'till they drop...

[Darth Raptor]

Earth doesn't need any of us. If the entire human species just up and vaporized the earth would have an interesting climate for a few thousand years, another ice age maybe, but then it'd go on being filled with life and happy.

For how long? Another billion years or so? Earth very much does need us. Although I agree that our tenure as dominant species has been rife with tragic irresponsibility thus far, we are the only hope life on this planet has for indefinate, long-term survival.

A sapient race is the only thing that can protect us from a meteor impact, and it is the only thing that will enable life on Earth to outlast the star on which it currently depends. Homeworlds are not the nexus of a civilization, they're merely a birthplace. The planet, like all things, is mortal. The only thing immortal in the universe is a dynamic and self-replicating intelligence.

How long did it take Earth to evolve intelligent life? 600 million years? If we buy the farm as a species, life on Earth may not get a second chance.

[Lagmonster]

As an aside, people who worry about overpopulation scare me. I mean, a lot of people care about the environment but most of them at least don't go about wishing I wasn't alive.

As for the minimum population, well, it can technically be as low as a stable gene pool will allow. But a minimum population maintaining our most comfortable lifestyles takes a surprising amount of people dedicated to secondary and support and maintenance roles, and the more people you have for that, the more you need to handle the greater diversity in medical conditions, increased food production, etc.. It could take a while to narrow it down to a good number, and even then you'll probably have someone rationalizing that another pair of hands would make things better as long as your infrastructre supports it.

[kheegster]

As an aside, people who worry about overpopulation scare me. I mean, a lot of people care about the environment but most of them at least don't go about wishing I wasn't alive.

Isn't that the same logic as saying that contraception is murder?

[Surlethe]

As for the minimum population, well, it can technically be as low as a stable gene pool will allow. But a minimum population maintaining our most comfortable lifestyles takes a surprising amount of people dedicated to secondary and support and maintenance roles, and the more people you have for that, the more you need to handle the greater diversity in medical conditions, increased food production, etc.. It could take a while to narrow it down to a good number, and even then you'll probably have someone rationalizing that another pair of hands would make things better

The more people you have, the more money you need to keep the economic standard high, which means at a certain point, everything maxes out. There should be a pretty definite point where marginal humans begin to take the economic standard back down.

Of course, I'm not at all sure where to start tackling this monster of a problem.

[Broomstick]

How long did it take Earth to evolve intelligent life? 600 million years?

You're a little off the mark there.

From the first life that left relatively undisputed fossils to us was about 4 billion years.

[Master of Ossus]

I think that the current economy could function pretty well if there were a gradual drop down to about 60% of the planet's current population. Services and businesses would be scaled back proportionately to the population, while major facilities degrade.

[Spyder]

I think there's a little bit of underestimation on our reliance of third world labour.

[Lagmonster]

As an aside, people who worry about overpopulation scare me. I mean, a lot of people care about the environment but most of them at least don't go about wishing I wasn't alive.

Isn't that the same logic as saying that contraception is murder?

Not entirely, but I understand what you mean. I've heard 'population scares' coming out of the environmentalist crowd stating that we have too many people NOW, and that things like having a war every once in a while is actually good for population control. Granted, that's the loon factor, but a surprising number of loons work in high places in environmental policy.

[Zero]

The people that think war is good for population controll must ignore that there's always the result of many more children after large wars. I mean... think about the crap after WW2. There was a significant population reduction in the two world wars, but the reproduction that was done to make up for it has made up a bit much, and now some folks are worried about overpopulation. Wars aren't good for much except incentive for technological advance.