Let's suppose the population of mankind grows by 1% each year from now on. That's fewer then the growth rate we had during the 20th century with all it's wars.

Then you calculate the size of the world population next year by the following formula:

s_n * 1.01 = s_n+1

The population a year after would be calculated by:

s_n * 1.01 * 1.01 = s_n+2

The population in the year x after the year we start is:

s_n * 1.01^x = s_n+x

So how many years does it take at such a reproduction rate to get a global population of 500 billion when we start with 6 billion?

6 * 1.01^x = 500

1.01^x = 83

x * ln 1.01 = ln 83

x = ln 83 / ln 1.01

x = 444

Already in 444 years we would have a population of 500 billion. The human mind didn't really evolve to grasp exponential functions for which reason a lot of people have problems with interest. It's not only disadvantageous to us in the modern business world that we don't directly the the effects on interest on interest but also when faced by the actual growth rates of biological systems.

If we would now take the current factor of annual enlargement (1.2%) we would already reach 500 billion in 371 years. And if we take the reproduction rate of the golden 60s (2.1%) we would reach 500 billion in 212 years.

If you mean literally abandon the planet, I'd figure that won't happen until Sol swallows it or makes it otherwise uninhabitable. Barring a black hole or other phenomena. And our own extinction.

If you simply mean spread out to colonize, I'd say 50 to 100 years.

Maximum world growth rate in the last 100 years is just over 2%. Do you think a world space program with 5 to 10 billion (1-2% growth on 500 billion) people leaving the planet every year is feasible??

Fortunately world population looks set to level off somewhere around 10 billion around the middle of this century.

By many estimates this still significantly above the long term sustainability level, and the impact of climate change is likely to reduce the food production capacity of the planet, so it seems we do have a problem.

When I was young I watched Star Trek and was very optomistic about our future.  Over the years I grew less so.  Unless we come up with some incredible new technology soon we will not be going very far into space.  The Earths resources are finite.  They are already under stress and soon we will be reaching a point of no return.  Most people believe in a magician who is going to step in and make everything OK, maybe after giving us a good scare.  Well its not going to happen.  We are like someone dying of heat stroke and 1 blanket per minute is being layed on us.  The best any government has proposed is to only add 1 blanket every 90 seconds.  No one is proposing to reduce greenhouse gasses.  Only to slow the rate 0f increase.

That is only one aspect of overpopulation.  Over a billion people live on less than a dollar a day.  Some call them developing countries.  Its not going to happen.  I think the difference between animals and humans is that we know sex causes babies, and we can use birth control or even abstain,  But people will not do either.  In the US, in 2007 there were over 4 million babies born.  More than any other year in history.

WE are going to see mega-famines like never before.  We are going to see wars that will kill many times the wars of the twentieth century.

Some fools moan about abortion and birth control as being against god's will.  can you inagine how they will rant about some government telling them how many kids they can have.  China did a noble experiment but people aborted females in favor of males.  Mistake, Now there is a shortage of women and China is begining to eye its neighbors with lust.

What can be done?  My wife and I decided to have one child.  Good luck trying to get a mormon to do that.  We live in interesting times.

Not true at all.

Baseless conjecture.

Well, I guess you haven't heard of Malthus then.

Cancer is merely unregulated growth. We are currently experiencing unregulated growth. Hence the metaphor holds. Unregulated growth leads to resource exhaustion, which leads to massive die-off. Malthus. We are the cancer.

See, I really don't think you understand the point. The point is mass extinction and ecological collapse. You are assuming that humans can live without other organisms such as animals and plants, especially zooplankton, and algae. If these die off, the Earth could not even sustain 1 human, let alone billions.

Human populations displace other organisms which leads to mass extinction. We are *already* in a period of massive extinctions (known as the Holocene), on par with the mass extinctions of the past, such as the Cretaceous, the Permian, etc. Too many extinctions leads to ecological collapse, which means the whole ecosystem dies. Enough ecosystems die, and humans will die with them. All that will be left are the most primitive forms which are incapable of sustaining human population.

The only way humans could survive in such an environment would be to supply their own sustainable self-contained environment, which is the same problem as a space-ecosystem. However, you're still talking about gigadeaths. That's not a viable solution.

I didn't say that. You're putting words in my mouth. I said that if A is where we are now, and C is sustainable space ecosystems, then to get from A to C requires us to pass through B, which is sustainable Earth ecosystems. So, don't put all your eggs in the C basket, we should focus on the B basket as the primary solution to overpopulation on Earth. We didn't get from vacuum tubes straight to integrated chips. We had to pass through the transistor phase first.

I am pro-solarsystem-colonization. However, it is not a solution to overpopulation on Earth. We still need to solve that problem first, and solar system colonization tech is not a short-cut in any way.

On the contrary, it is very true. It is even an understatement. We could have hundreds of TRILLIONS of people.

Baseless conjecture my left testical. Invalid response.

Not even a factor. Why are you people thinking in 2 dimensional terms anyway? We could take as much room as we currently do a billion times over and still have more space available than we'd know what to do with.

The vast majority of the damage we cause the ecosystem is damage we could stop or reverse if we had a mind to. When it becomes a sufficient pressure to adapt to, we will adapt to it. Or we will die. Overpopulation will not be an issue.

That's besides the point. You still haven't shown me the cancer. Until you do, your metaphor is irrelevant.

We aren't seeing unregulated growth, for one thing. For another, the cancer only becomes a threat when it encounters a vital organ or the like. A cancer on the skin, for example, can grow forever and never cause a threat to the life that sustains it.

You're simply going to have to choose a better example.

No, we aren't. Our growth is currently highly regulated by disease, famine, and war. And various government policies.

Hence it does not.

As I mentioned more than once, we only have one natural resource that is in true peril, and we are on the verge of substituting it en masse. You're going to have to do better.

Actually, I hadn't seen it. The PC I'm on must have cut part of your post out, or you added to it after I'd quoted you. I'll deal with it now.

I don't think you do either.

No, I'm not. You just keep popping up strawmen that have nothing to do with reality.

Not if we manage ourselves properly.

I don't disagree. I also say it is irrelevant. You're going to have to prove that we are incapable of halting our own destructive agendas in order for your points to make any logical sense.

And you are thinking in two dimensional terms. When you break through into the third and fourth, let me know.

You may not have said it, but you implied it. I put nothing in your mouth. Be more specific next time.

To which I pointed out that studying C would help us understand A and B, to which you have failed to refute me.

Now who's putting words in who's mouth? I never said to put all of our efforts in C, I said to put some efforts, as it would add to our comprehension of A and B. You still haven't successfully argued against this fact.

The process would have been sped up if we'd had integrated chips around to study, now wouldn't it? Your logic is extremely lacking here.

There is no problem to solve.

No, we aren't.

That does not mean we are facing unregulated growth. It means we are facing growth.

Just means people are fucking more often than dying. It does not mean our growth is unregulated. If it were, we'd have already gone extinct from overpopulation.

You continue to ignore the third dimension, which removes the ecology from the debate, and therefore keep tying yourself into knots that go nowhere.

And what if we had a million times the energy with just as much algae as we have, or more?

It solves it too. You obviously haven't given the topic its due consideration.

I didn't say it was. I said it is regulating our population. Nothing you've said proves otherwise. I stand on my points.

One could argue that WWIII has been in progress for some time now. Though that's not the point.

You are adding in additional assumptions that the OP was not talking about. You are assuming that we can come up with a sustainable ecology *before* our current population growth causes serious problems. The OP was asking about the *current* serious problems, and how we can manage population growth before we get the tech.

The problem with your argument is you're basically saying, "Assuming we can solve all these technical problems with new technology we don't yet have and can't really see on the near horizon, well, heck, I just don't see what the problem is!"

Of course, if we had the right tech, most of our problems would be solved. However, we *don't* have the tech.

And besides, even if we had the tech to harness as much energy as we could, that still doesn't stop the destructive effects of uncontrolled growth. We would basically become all-consuming space bacteria. This is a future we should avoid, as it will lead to enormous suffering. We need to be able to grow sustainably and peacefully, without generating more suffering than is unavoidable.

So, it is not strictly about tech, there also needs to be a cultural change so that we regulate our growth.

An example: There's a human cell line that has become a malignant infection of lab cultures. Essentially some woman years ago (don't remember her name) had a tissue sample taken from her and grown in a lab petri dish. Well, the tissue reverted to an amoebic-like state where it started to grow uncontrollably, and took on a life of its own. It spread from petri dish to petri dish through contamination.

And now, even though the original woman is long dead, this cell line goes on living, and is several times her original body mass. Despite efforts to control it, this aggressive cell line persists to this day.

Now, our situation here is that we run the risk of becoming like this malignant cell line, spreading and multiplying indefinitely.

The problem is that there's only so much space and only so much energy. Eventually, we will run out of space and energy and conflict will start again. But *this* time, there will be trillions and quadrillions of humans, instead of mere billions. Massive war and conflict would be the result. Immense suffering.

And all because we didn't solve the problem of unregulated growth.

An embryo growing into a human adult is regulated growth. It grows to a certain size, and then stops itself. A cancer cell or a malignant cell line is unregulated growth. It grows and grows until it consumes all resources available.

Watch Akira. Tetsuo can't control his own growth and ends up killing Kaori.

Mass extinction is already a reality. You have not addressed the ecological concern. You assume we will get the tech to support sustainable enclosed ecosystems *before* mass extinction causes a problem. This is an unjustifiable assumption on your part.

Correction: *Assuming* we manage ourselves properly before massive human die-off.

This is a bad assumption. We are *currently* killing off thousands of species per year. The OP was talking about 'What if this trend continues?' You are pulling out your magic tech wand and saying, "It won't continue. There is no problem." You are simply blind to an *existing* problem that will only get worse unless we do something to change the culture.

No, I only have to show that we need to change our destruction *before* it's too late and the damage is done irreversibly. Considering that the problem already exists, this is a no brainer. You're just hiding your head in the sand.

You are assuming we can escape Earth before ecological collapse. This is a massive and unjustified assumption.

As long as a large number of humans are stuck on Earth, it is a two dimensional problem, as the surface of the Earth is limited to two dimensions.

If you are talking about sky scrapers or something, then you are more naive than I thought.

No I did not imply it. Be less presumptuous next time.

I don't have to refute you. You just conceded that B comes before C. It is B we need to accomplish to fend off ecological disaster. My point stands. B is higher priority. B must come before C in time. That's all I need to establish.

But we didn't have ICs, just like we don't have sustainable space ecology tech. In fact, it's the other way around. Achieving transistors first allowed more complex computers, which allowed semi-conductors to be better understood, which allowed the miniaturization of transistors, which finally allowed ICs. The more primitive step was a pre-requisite to the more advanced step. Sustainable Earth-bound ecology tech is a pre-requisite to sustainable space ecology tech.

Your head is in the sand.

Yes we are. Nyah nyah nyah.

You misunderstand unregulated growth. It does not mean 'really fast growth', it means 'growth that does not have any way to stop except exhaustion of resources'. Even if the growth rate were 0.001% it would still be unsustainable. It would just take longer to hit the limit.

A 1 percent growth rate means population doubles in approx. 70 years. Unregulated growth means that continues until resources are exhausted. Some of our resources are themselves living biospheres, which can also be killed off. We are *already* killing off species at an unsustainable rate (100 times the background extinction rate; arguably faster than other mass exinctions of the past). It's a recipe for gigadeath.

Then you may be able to get some humans in space, but you would still have gigadeath down in the gravity well. And eventually, humans would grow to consume all that energy anyway. At most you would be delaying the problem.

Sorry, it's clear I've given it far more thought than you.

The ultimate resource cap is the speed of light, which ensures that we cannot colonize the universe faster than a cubic rate. However, any form of unregulated growth will always be exponential. And, if you knew anything about growth curves, you would know that exponential always overtakes polynomial, given enough time. You will always exhaust resources if you do not regulate growth.

Even if you could colonize space at the speed of light, and collect all the energy available at 100% efficiency, you would still run into resource conflicts eventually with unregulated growth.

Like I said. Clearly you don't understand Malthus.

It is not regulating our population. In fact, war and famine are a result of a *lack* of regulation, which manifests as resource conflicts. Back to biology 101 for you.

What do you mean "two dimensional terms"? A surface is a 2 dimensional construct, so yeah, of course. Please address the point with some actual specificity instead of the vapid response "Not even a factor". It is a factor! That's a tremendous population density. In fact, that's an insane population density. Ever heard of Malthus? For a K-selected population at high density, the proliferation of disease will increase drastically. It wouldn't be possible to get the population density that high, anyway, for that reason. Like all limiting factors for K-selected populations, density-dependant factors become more limiting as population increases.

Why do you keep making ridiculous assertions and then not backing them up, such as "we could take as much room as we currently do a billion times over and still have more space available than we'd know what to do with"? I'm a little unsure how to interpret this. Are you actually suggesting that with one billionth the space we have now, we'd still have more than we now what to do with?  For a K-selected species like H. sapiens, density will be a growth-limiting factor. We could never get the human population on Earth to 500 billion anyway for that reason.

I refuse to talk to you again until you read a textbook on population biology and biostatistics. Read this entire textbook:

http://www.cambridge.org/uk/catalogue/catalogue.asp?isbn=9780521825375

Or I refuse to continue this conversation

Lol it's Jacob Zuma dancing (my future president....hopefully not though)

No i am merely saying If correctly managed it is no problem, If it isn't then it is really only a huge problem for the 3rd world. 1st world counties are really in no danger of overpopulation. Look at population models/pyrimads for first world countries. Most are in the fourth stage with slowly increasing populations however some have moved onto the fifth stage with decreasing then incresing populations averaging out at no growth. Don't get me wrong there are a hell of a lot of work we would have to do across the board for 3rd world counties to be ok but with there current economies they probably wouldn't be. Still that isn't the end of humanity.

I'm assuming nothing. I know we can. The only question is whether or not we will.

And you have failed to refute anything I've stated regarding it.

I'm not saying anything of the kind. We already have the technology to save ourselves on Earth. As for space flight, you are assuming that we will not gain technology despite persuing it. And I'm the one who's mistaken? Try again.

Lies. We've had the right tech to replace gasoline powered motor vehicles for decades. It still hasn't been done. Why? Because there's been little need to make the transition. That does not preclude the possibility of the transition. This is merely one example out of millions of examples or the failure of this particular argument.

The third dimension does that. You continue to ignore it. Are you becoming a theist?

And yet again, you still haven't proven your assertions in the face of mine.

Aha, some meat. Something I can even agree with. Perhaps you were assuming that I thought we could continue with our current methods and retain sustainability in the face of excess additions to our population? Let me assure you this is not the case.

I couldn't disagree more, unless we continue haphazardly and without restraint. Doing so is impossible, as pressures will destroy us if we ignore them. Long before overpopulation would become a concern.

There is trillions of times as much space as you give credit for. Perhaps whatever comes after trillions. Quadrillions maybe?

That is inevitable regardless of what we do. Entropy.

The problems you envision will ocurr no matter our population. It is simply a matter of time. Getting off of Earth can extend it, but nothing can stop it. Save perhaps the gaining of knowledge on how to create a universe. But that is wild speculation.

Again, you have yet to counter my examples showing that human population growth is regulated.

I don't think I need to watch an anime for the purposes of this conversation.

I already agreed with you on this point. Bringing it up again is pointless.

You have not addressed my response to your fictional ecological concern: The third dimension.

Strawman.

If we don't, then we die. End of story.

Hardly.

Again, we've already agreed on this.

We have gone far beyond the constraints of the OP. My response to the OP was short and simple, and stands unrefuted. We are now discussing your concerns.

Strawman 2.

I thought we'd blown them away. Meh.

A bald faced lie.

Strawman 3.

Just because the surface is two dimensional does not mean we must also be. In fact, we aren't. Look who's head is really in the sand.

Skyscrapers are merely one of two directions we can build in. And you are the one who is naive.

Yes, you did imply it. You proved it with the continuation of this line of thought. 

Yes, you do.

You again fail to refute that a better understanding of C allows for a better understanding of A and B.

Thank you for conceding my point and destroying your own argument. I'll leave the rest of this particular line of discussion alone, as there's nothing left to deal with.

Says the pot to the kettle.

No, we aren't. Nya nya nya nya nya.

Perhaps you do, but I do not.

Which is in no way what we are experiencing today, except perhaps with oil.

I think we're just talking past each other in regards to the definition of regulated/unregulated. I suggest we drop it altogether, as it has little bearing on the end result anyway, when I take into consideration where you're coming from.

You still haven't proved that we're incapable of stopping it, or even stopping it before it's too late. And it is not yet too late. Your sensationalist claims of gigadeath is just that: sensationalist.

Still haven't proven that.

If you're wanting to get into the nitty gritty, nothing we do will prevent the problem. Only delay it. Even a fully regulated and sustainable population will run out of resources and time. Staying on Earth will speed up the process by a factor of trillions. Your arguments are self defeating.

Obviously not.

Now I think you're getting ahead of yourself. We are not even sure we can colonize beyond our solar system, let alone beyond our galaxy.

Due to entropy, the exhasution of all resources is inevitable. If that is the focus of your argument, then I'll agree that we have no future at all, and there's nothing we can do about it. I do accept that as a likely probability, if not a certain one. My focus is on prolonging our existence. Which is easy enough to do, as long as we manage ourselves and our environment better than we do. 

It'll happen anyway.

Obviously you are the one who does not understand.

War and famine are nature's regulators. Regulation is not dependant on direct human influence. If we don't do it, the Earth will do it for us.

Edit for clarity in italics

Never mind. I don't have $150-180 to throw around.

 People seem to be forgeting the time frame here. 10 billion by 2050 really doesn't seem that bad at all. Really look at china with a population of 1,330,044,544. Other countries still won't be up to that point by 2050 except india. I really can't see what the fuss is about there is alot of time to work it all out.... besides http://news.bbc.co.uk/1/hi/sci/tech/1467252.stm 

Yup I did see that,  I believe he is talking about fossil fuels, already been discussed. I don't see how he can be refering to anything else. maybe you can though.

Something like that. Could you very specifically elaborate what you mean by using the third dimension? Are you imagining above and underground living space such as sky scrapers and caves? Won't the limited amount of biomass available on the world stop us from increasing farm sizes without limits? And no, hydroponics is not a cure for that problem. One way or another we will have to displace other biomass on earth to grow without limits. That has to result in the deaths of other species. We can't take larger and larger cuts out of the pie without limit. And wouldn't space travelers with their self-contained ecosystems actually be taking the earth's biomass away forever? They would leave with clean water and plants and air and nitrogen to fertilize their space-ship hydroponic farms and maybe animals; and then we would never get those resources back. They aren't going to mine biomass out of asteroids or Neptune's moons. Unless they bring in a lot more hydrocarbons and water than they leave with, then they are screwing the people left behind.

Yeah, I was using the word 'biomass' very loosely.  Water, hydrocarbons, nitrogen, phosphorous, and all that good stuff is what I was talking about. Thanks to exponential population growth, if fleeing to space is used as a pressure release vavle for our population on earth, there will be limitless amounts of people who will leave. Allowing limitless amounts of people to leave would only open the door for equally limitless population growth. Only stripping our planet's ecosystem of its vital resources will put a stop to that. And we could do it in your optimistic view of the future. Now, if we could find other significant sources of water and hydrocarbons in our solar system then we could use those as resources to sustain space dwellers without leaching irreplaceable resources from earth. That's the problem here, we can breed indefinitely, but even a tiny amount of resources being taken away permenantly each generation would be a rapid descent into a planet devoid of macroscopic life.

   Heres a good argument about overpopulation and a rebuttal  www.alternet.org/environment/130843/are_we_breeding_ourselves_to_extinction/page=entire

 and the rebuttal www.alternet.org/module/printversion/131400 ,I didn't get a chance to read them both .  

...Are you kidding?

If you're a wide-eyed, crazy optimist, you honestly believe that the planet can likely handle about 4.4 billion human beings. Anything beyond that and you simply cannot be taken seriously.

How many aquifers are there in the world? How many liters of water does each aquifer contain, how much does it gain back each year, and how many liters of water is required per person per year? How much total farmland is available? How many net calories per acre, at maximum, can we yield from that farmland while it is still arable? How many generations of crop can we grow from it before the topsoil is no longer arable? How many calories does each human being on Earth require per year to remain healthy?

Vastet, are you aware of the work of Norman Borlaug? Borlaug's 'Green Revolution' was, essentially, the very reason we've been able to reach our pesent point. Thanks to agricultural engineering, we've really been able to squeeze the calories out of our fields and with minimal human caloric input (we've been using fossil fuels to shoulder our weight) - but, unfortunately, even this monumental work (Dr. Borlaug really did save humanity's collective ass) has it's limitations. For starters, we're running out of accessible fossil fuels. Heavy agricultural equipment cannot operate without them and modern fertilizers & pestcides cannot be synthesized without them.

The looming predicament is rather obvious. How do we continue feeding an exponentially growing population with a limited (and dwindling) ability to harvest food? And if we cannot, who is going to volunteer to starve and/or dehydrate to death for the benefit of strangers?

While I'm also a proponent for space exploration in the future, we cannot pretend that potential, speculative technologies for the future are any kind of solution to our present-day problems. We have many, many, many years to go before we'd be space-worthy, and we cannot get there if we corner ourselves into nuclear oblivion in the interim due to food/water/hydrocarbon shortage.

Anyone who talks about overpopulation not being a problem *without* addressing the mass extinction and ecological collapse issue (e.g. both Vastet and this rebuttal article) are simply denialists with their heads in the sand. Sorry. It has to be said.

Study evolution and population dynamics. Study past mass-extinction events. Study the current Holocene mass extinction event which is human-caused. Put two and two together.

Now, I ask you, what is a population crash? If you haven't got a solid answer for that, you need to go back and do more research.

This overpopulation denialism is as bad as global warming denialism. Perhaps worse.

They're a married issue, IMHO.

The 'rebuttal' article is a joke. It's another Crichton-esque, "Oh, they're just using that issue to steal away the spotlight from my pet issue!" argument. Take what they've said about the birth rates in the developing world:

"Moreover, the few countries that still have relatively high birth rates, such as those in sub-Saharan Africa, have the least impact on environmental factors such as global warming."

This is just flatly wrong. Africans don't need to eat, drink, receive an education, etc? Curious that the author then goes on a rant about how ecologists are apparently just trying to mask the issue of ugly politics in Africa, given that their argument hinges on the notion that Africa remains undeveloped.

Wow, I knew I was opening a potential can of worms, but I really wasn't expecting a debate on whether overpopulation is truly an issue.  I've been sick over the last couple days or I would have chimed in sooner. 

It's nearly unfathomable to me to think that we can just grow our population infinitely without completely ignoring the environmental consequences.

To me we have already thrashed the earth, and it's species, ecosystems, resources etc.  I'm not even an environmentalist either.  To think that we can rape the earth even further, and not face dire consequences is naive at best.

One thing that weighs on my mind, that hasn't been addressed as much in this thread is some sort of proactive measures.  What do you guys think those should be (assuming that overpop. is a serious issue.)

 I agree with Natural.  The only thing that has ever been consistent in decreasing the voluntary birth rate has been education.  The world over, people with more education have less children.

More education also (I think...) correlates to more environmental responsiblity, but I'm only extrapolating that.  I haven't seen a study specifically demonstrating that.  

There is no easy solution.  The best solution I have heard is to use orbital platforms to send microwave energy down to sterilize segments of the population.  Stop howling.  I said best, not most popular.  If just the cities were targeted the damage to the biosphere would be minimal.  I believe there would be some opposition to this plan especially among the various superstitions.  Do you think this is worse than what is going to happen if nothing is done?

Superstition rules,so we have to go to plan B.  You can decide for yourself to have fewer children.  You can drive a smaller car.  You can have a smaller well insulated house.  You can grow some of your own food.  There is going to be a period of adjustment.  The only question is weather we impose it upon ourselves, or weather nature imposes it upon us.

Ummm... have you been listening to Coast to Coast AM?

I'll be honest.  I don't think there's any realistic hope.  If we had another five or six centuries to work on ridding the world of religion, that would be one thing, but so long as people believe that 1) people are special, and better than other organisms,  and 2) God wants them to make more people, then we're pretty much fucked.