The world population is growing because the birth rate exceeds the death rate, so to stabilize the world population either the birth rate needs to drop, or the death rate needs to increase. The most cited reference for population studies is the projections of future population (PDF) made by the Population Division of the United Nations. The UN report projects the world population to eventually stabilize as a result of countries settling in to a birth rate that falls around the replacement level.
A commentary by Stephen Warren in the open access journal Earth's Future takes the UN report to task for focusing on birth rate. He notes that all species generate offspring in numbers well above the replacement level of two, but you don't see historically the kind of population growth like you do with humans. He argues that despite all the negative feedback mechanisms on population (such as war and pestilence), it seems that Malthus (PDF) was correct that food supply is the driving factor, and wonders whether it is even possible to stabilize the world population until food production levels off.
(Score: 1) by WillAdams on Wednesday May 27 2015, @03:19PM
Yes, conflated potassium w/ phosphorous. Thank you for pointing that out. My thanks to the AC for noting that the two are inter-related to a degree.
(Score: 0) by Anonymous Coward on Monday June 01 2015, @10:36AM
It's whichever that runs low/out first...
Sustainable growth is an oxymoron on a finite planet.