World population of 11 billion by 2100.

[septimus]

I’m glad to see responses more intelligent than the usual: Heard about overpopulation; got the T-shirt; they were wrong.

Here are excerpts from Stranger On A Train’s post estimating sustainable human population:

@Stranger_On_A_Train

Even given the technology of grain cultivation that gave rise to modern high density civilization, the current human population has unambiguously exceeded the natural carrying capacity of the Earth in terms of food production. The Haber–Bosch process, which binds atmospheric nitrogen into ammonia, is used to manufacture the artificial fertilizers that permit the large scale modern agriculture of the Green Revolution… A similar limitation are naturally occurring phosphates.

Another fundamental limitation are natural sources of potable water. … modern agriculture currently uses unsustainable volumes of ‘fossil water’ from underground aquifers well beyond rates of replenishment, and the overuse is actually compacting the aquifers so that they cannot carry the same future capacity…

Of course, one can posit some future technology … [but it would take] more energy and (especially in the case of water) transportation to the user site, which places additional burdens on a fuel economy currently dominated by non-renewable sources.

… If the entire population of the world lived at the same quality of life and attendant wastage as North America and Western Europe (as many developing nations are currently aspiring to do) there would be extreme burdens on current resources, especially agriculture and fossil fuel usage.

For ultimate sustainability without assuming near-magic recycling and energy production technology, a population of somewhat less than one billion people living in modern urban lifestyle is probably a realistic estimate.

Stranger