Back in 1976 my mother took me to see a psychologist. I was essentially blowing off school and everything I wasn't interested in and she wanted me to focus on what she wanted me to focus on.
I was trying to explain to this guy why the human race would eventually have to live in huge buildings that took up the smallest land foot print, built in places like mountains. He couldn't understand and I would guess that my teen age explanation kind of sucked.
What it comes down to is farmland. As population increases farmland becomes more and more important. Eventually we will have to recover as much arable land as possible to feed the population of the Earth. That means recovering farm land currently underneath cities and suburbs.
Back then I didn't think people were stupid enough to use nuclear weapons and destroy the Earth. By the time I had been trained in Chemical, Biological and Nuclear I believed that the most serious threat was Biological followed by Chemical.
When I heard the conspiracy theories about AIDS and Ebola being released in Africa as tests by the United States government to develop a biological weapon I was (and am) pretty skeptical. It does make a convoluted sense, but, there is no way to determine who would be killed. If any government were trying to kill off enough of the worlds population to give the world time to develop solutions to resource problems the disease would have to kill "cleanly" to minimize the resources necessary for recovery. Then the disease would have to target "surplus" population, elderly, disabled, terminally unemployed, and redundant positions.
The truth is that it would be impossible to create a disease that targeted so specifically and the problems created by the randomness of such a disease would far outweigh the benefits. The potential for virus mutation is very high. Because of the typical indecisiveness of politicians they would probably wait too long before releasing that kind of weapon any way and Karma necessitates the virus would mutate so that inoculated people would become more susceptible anyway.
I thought the scenario in 12 Monkeys much more likely, but, we are talking a millions to one shot rather than the billions to one shot of a government releasing a disease.
Unless a disease occurs naturally, and I don't count out that possibility, we are going to deal with over population and dwindling non-renewable resources.
Historically it takes 1.25 acres or about 0.5 hectares of land to support a person and there are currently around 4.4 billion hectares of farm land so with production issues we can support about 4.4 billion people in the world.
Sometime in the next century population increases and non-renewable resources will cross and the world will rip itself apart, unless, we can figure out how to cooperate.
We won't cooperate though because people are essentially stupid and refuse to understand or accept even articulate arguments. People won't change their opinions based on facts, much less deductive arguments.
Instead the world will wait until we are past the "cliff" so we and our world will suffer because of our own stupid choices. When stuff becomes really bad nations will blame each other and I expect the nukes to start going off.
Which kind of makes the whole "New Earth" thing in the Bible make sense because in order for people to continue existing we are going to need a "New Earth".