saturation point for world population?

Have any studies been conducted to determine the absolute maximum number of human beings that the earth can manage? I remember a discussion I had a long time ago with a very sharp friend of mine (where are you PJAW?) - he told me about the law of energy conservation: the planet will not gain more weight(or mass or volume or something) due to the increasing population, because we will use up the resources at a rate propotional to the increase in humanity. Or something like that …

So, what’s the straight dope? Have advances in science and technology (as applied to average lifespan) enabled humankind to approach the disaster point? Is it possible to create a doomsday scenario based solely on the number of humans on the planet? I’m not talking about wars or famines or catastrophes usually associated with overpopulation - I mean a drastic emergency due to the mass or weight or volume of human beings existing on this sphere spinning in space.

Or have I had too much rum this evening?

Gotta go with the rum. Shit, the earth picks up several tons a day due to cosmic dust and such. Besides, do you remember the law of conservation of energy? Applies to matter, also. People don’t just ‘appear’, we’re built from ‘earth’. A person can only gain the same amount of weight the earth loses. Hence, ignoring outside factors (said cosmic dust), the earth as a whole is always going to weight exactly what it has forever and ever in the past, regardless of the number of people, plants, animals, or sex toys.


Isaac Asimov once wrote a column on something like this called “Life’s Bottleneck.” He calculated the percentages of specific elements that make up cells, as compared with the total amounts of those elements in the earth’s composition. The details are fuzzy; it’s been many years since I read it. I don’t remember if he was calculating for humans or for for living cells in general. I’m pretty sure that life’s bottleneck turned out to be phosphorus. The amount of phosphorus present in the earth only permitted a certain number of living cells to exist, due to how much was needed per cell. Of course this is true for any of the necessary elements, but phosphorus was the one that minimized the total. You might be able to find the article online; I don’t remember which of his 400+ books it was reprinted in.

If you ask me there’s too many already. Will some of you please get off the planet?

“Asps…very dangerous…you go first.”

I have found 2 references to the mass of all life on the earth. One says the mass of all life in the oceans and below ground (excludes life above ground) is 10[sup]16[/sup] kg. The other says the mass of all life is 10[sup]15[/sup] kg. I’m quite sure the second is a wild underestimate; the first may also be an underestimate. In either case, the weight of humanity is probably not much more than 10[sup]12[/sup] kg. Therefore humans probably make up no more than one part in ten thousand of all life on earth. I strongly suspect it’s even less than this.

I’m not too worried about the population. People look around them and see crowding. What they don’t see is the millions of acres of undeveloped land around the world and around the country, away from the cities and suburbs. There are about 8 acres of land for every living human (not counting oceans). If the island of Manhattan were as densely populated as the average of the rest of the world’s land, its population would be about one-and-a-half thousand instead of one-and-a-half million.

Not as scientifically useful as the figures anyone else posted, but rather humorous, I thought, are the following calculations. Assuming that as of the year 2000, there are 6×10[sup]9[/sup] humans on Earth, and that that number is doubling every 40 years (an outdated figure I believe, but close enough):

In 2716, the entire land mass of Earth will be covered with nothing but shoulder-to-shoulder people, in one big global mosh pit.

In 3767, the entire mass of Earth itself will have been converted to human flesh, so that we’ll form some kinda big organic ball, I guess.

After that point, the human ball of flesh will get larger and larger, until 5228. That year, the 11783434727986903979440592762207000 people will form a ball 52005718216 meters in radius, and that radius will be increasing at the speed of light.

The tangent that this thread has (inevitably) started to veer toward has been exhaustively hashed out in this thread:
6 Billion?

The short answer for expected population growth is that it will peak and begin to fall within the foreseeable future with expected absolute population falling not long after that.

For specifics, look for posts by dhanson, divemaster, and Akutsami.

I’ve noticed that people who are “religious” have many more children than those who aren’t.
My friend, whose about 37 has 12!
Could we actually over populate the planet? And what proof would there be; meaning theres not enough food? I guess it depends on what you’d call food, in that circumstance.
I’ve already had one. But I promise not to have more than 2 more, if I do.:slight_smile:

Akatsukami. Sorry.

Achernar: Hilarious! Great post! :slight_smile:

To get back to the OP: I don’t think the weight or mass of people is (or ever will be) a problem. The mass of people is entirely a result of the mass of food that people eat and liquids they drink, so there will be no change in the Earth’s mass as a result of increasing population (unless we start to import food from Saturn or something).

Also, the problem with overpopulation isn’t space. There’s plenty of room for people on Earth. The problem is that all these people need food, clothes, clean fresh water, shelter, and they all want things like cars, computers, etc. As the population increases, our expenditure of natural resources increases and our production of trash and human waste also increases.

How many people the Earth can sustain depends upon how long you want them to be sustained. If you only look a generation or so ahead, the Earth could support 16 billion or so people. If you want to look a century ahead, maybe 12 billion, or if you want to look millenia in the future, 4 billion or so could be sustained.

The numbers above are all vague memories and not exact, because I don’t have the cites with me. If anyone asks, I’ll dig them up. A good place to look are the Worldwatch Institute’s State of the World yearly publications. Like this one.

Achernar: 11783434727986903979440592762207000 people…hmmm…I’m thinking when that time comes they will all be ahead of me in line at Motor Vehicles.

I read somewhere that the Earth’s “carrying capacity” for large apes (guess what we are, folks!) is about 200 million. The thing is, this assumes natural conditions, which haven’t prevailed for all of recorded history. How much potable water naturally reaches the Seven Hills? How many people could that support? Now, how much water was brought in by the Roman aquaducts? You see the pattern.

People don’t tend to realize or care, but we are part of the balance of life. If we get too overpopulated, we would not only not have enough food to live on, disease will run rampant in parts of the globe, and this will help cut back the human populus in order to protect the “greater good” of life.

Not that people in some parts of the world are not starving and dying of deasease already…

Hey, I just wanted to apologize, but my last figure was way off. Our human ball, for those of you who are concerned, will not be expanding at the speed of light until the year 8217. That should give you a couple more millenia to get ready. Also, at that time, the population will be on the order of:


and our radius will be 1637595264654725342 meters, or about 17.3 light-years. Really gives you something to look forward to, doesn’t it?

I don’t know what the answer is, but I bet it would suprise you.

I agree with wevets. Space is not the problem. The problem is that there are limited resources to feed/clothe/shelter us and there is a limited ecological capacity to handle our waste (pollution). A prime example of this is the water shortages experienced by many communities every year. Too many people using too much water and polluting other water sources at the same time.

Good point. It’s important to keep in mind that the carrying capacity is not a fixed constant, but changes according to conditions. Agriculture and water management are great examples of how we’ve changed the carrying capacity of our environment. In the future, the Earth’s carrying capacity is likely to be different than today’s.

Genetically engineered foods, for example, might increase the carrying capacity; while collapse of the world’s fisheries or the “asteroid winter” caused by a major meteroite impact (a la Alvarez) might decrease the carrying capacity.

That sig is a mental speed bump. I think I dislocated my prefrontal lobes saying it to myself.