Are you suggesting there are no limits to growth? No limits to available fresh water supplies? No limits to energy production?
Once you run you of fresh water and have to rely on nuclear power to run the desalination plants to keep people watered, you have three major problems.
> Are you suggesting there are no limits to growth?
There are limits to growth. We are just not anywhere near them, and don't seem to be approaching them. World birth rates are coming down fast enough that world population will probably never again double.
> No limits to available fresh water supplies?
Fresh water is a local problem. The world fresh water supply is renewable and renews at a rate several orders of magnitude greater than human consumption. Fresh water is a problem because transportation of it is expensive, and people prefer to live in places that have supply problems above places that don't.
Still, I expect that fresh water supply problems will mostly be solved by desalinization rather than migration.
> No limits to energy production?
Nuclear is limited really only by capital expenditure. Solar's limits are also vastly greater than any feasible demand, and it's getting cheaper.
> Once you run you of fresh water and have to rely on nuclear power to run the desalination plants to keep people watered, you have three major problems.
And what would those be? In any case, it makes little sense to desalinize using nuclear. Desalinization is a problem that's a perfect fit for solar power, as the capital cost of equipment is low enough in comparison to the energy costs that you can effortlessly vary production with the load, and the end product can be stored well.
I thoroughly agree with everything this person just said, with only one exception.
I would contend nuclear is limited only by politics. Removing the political impediments to new nuclear would help a lot. The capital risks are a political problem, not an economical.
Honestly, a cheap and infinite source of energy is all we need. Nuclear and Solar engergy is sooner or later going to be both cheap and near infinite. That is likely to solve most problems for humanity.
I also believe that nuclear/solar will provide us with our holy grial energy source; but we've been expecting this for the last 50 years so I don't hold my hopes too high.
The problem with freshwater is not that the global supply is limited, rather that supplies in some high-population areas are.
The Amazon river sends 209,000 cubic meters into the Atlantic every second[1]. That's 18,100,000,000 per day. A single human drinks about two liters (0.02 cubic meters) every day. There are 7 billion humans, so the global requirement is 140,000,000 cubic meters of water. The Amazon alone contains 130 times more than the global requirement for drinking water.
This is domestic consumption, which comprises 10% of water usage[2]. That means that 13 times more water flows through the Amazon than all of humanity uses. That's just one river.
First, 1 L = 0.001 m^3. A liter is one cubic decimeter. 0.1 x 0.1 x 0.1 == 0.001 .
Humans use more fresh water than just the quantity that they actually drink. You also have to include the quantity used for sanitation, personal hygiene, and recreation. Even discounting non-household use, a single person can easily clear 100 L (0.1 m^3) per day through their water meter, without even trying.
Go read your water bill some time. Divide your metered usage by 30.5 and restart your calculation on a new bar napkin or envelope. That gives you a multiple of about 26, if the whole planet consumes water like American households, and agricultural and recreational uses are completely ignored. Use that same 10% figure, and the whole Amazon could be completely consumed by only 18.2 billion people.
That's just one river, but it is the one with the most water in it.
Also take into account the much bigger amount that is needed to grow crops and feed livestock; you may be able to use graywater for that, but definitely not saltwater.
Also, water needed by industries and water spoiled by pollution.
Of course there is a limit. But population is soon going to start falling.
Look at https://en.wikipedia.org/wiki/Total_fertility_rate the chart on the right. We're currently at 2.36 fertility rate and falling rapidly. 2.33 is what is necessary for replacement. The US is at 1.9 and Europe is 1.59.
Once you run you of fresh water and have to rely on nuclear power to run the desalination plants to keep people watered, you have three major problems.