Even since Thomas Malthus’s 1798 book on the limits to population growth there has been an intellectual worry about humanity reaching its population limit. The problem is that there can not be an infinite growth based on a finite food supply. Malthus was unable to predict the vast increase in the food production because of the subsequent two hundred years of technological inventions, and during that time the population exploded from under a billion mostly hungry farmers to over seven billion mostly well fed non-farmers.
I have been one of the worriers, and still am in the long run if the population continues doubling every forty years forever, but as always, things are changing, and changing in non-predictable ways. One of the big changes is CRISPR, which is the developing ability to insert exact genes into precise locations on a DNA sequence. When the effect of a gene is known in one species, its effect in another one is often similar. Thus as these things become better known over the next several decades many species of things that are not food sources at the moment will become so, and as the total population is directly correlated to food supply the population will be permitted to increase. Or perhaps the total human population will decrease as wonderful new uses for plants are discovered and developed for other more interesting uses. It is impossible to predict what will be discovered, but with these new tools it is certain that there will be discoveries. It may be possible to grow machine parts. It may be possible to grow components of computers, such as memory devices and CPUs. It may be possible to grow plants that can filter desirable minerals out of sea water, or digest existing low concentration minerals into high concentration ores. There will be totally unexpected new things, and most of them will be good.
The shortfall of natural resources for an expanding population’s living needs other than food may hit harder than food. For example, metals such as copper are essential to our high-tech society, and there are few known resources. If we double the population we will need housing, transportation, and other things that need copper, and doubling the copper in use means doubling the amount that has ever been mined from the ground. Mine-able copper simply may not exist, and there is no good substitute, because silver is too expensive, and aluminum doesn’t work very well.
There are tipping points from obvious dangers, and there are unexpected black swan events from remote but real risks, but there are also preparations such as anti-fragile techniques of preparing for problems by building in multi-functionality into structures and processes. Also, there are standard techniques of always maintaining enough slack in the situations so you can easily recover, before your competitors do.
The problems are growing but our ability to cope with them is growing too.