Trimming the herd The advancement of life extending medical treatments, better overall health, unchecked birth rates in developing nations, and the containment of natural diseases, plagues, and even large scale wars are all contributing to a global population explosion. Check any graph in population and its growth rate up until about 1950 had seen steady but only nominal growth; then the world population went from about 2B to now over 7B in just 60 years.
At this rate, in the next 10-20 years will see global population extend beyond 10B people. I'm not a fatalist, but rather a pragmatist thinking that with all the global starvation we seemingly hear about, doesn't seem to curb birth rates. The absence of a global large scale war, and all its atrocities like that of World War II, where over 10 million men, mostly, perished. Though that seemingly is a small number, it only curbed the coming global birth rate for a few years when the baby boom generation in America, but also throughout the world seemed to have occurred.
I just don't see how the human race will be able to sustain itself over time without two possibilities helping it: 1) a natural or unnatural enhancement of the human body both physically and intellectual growth and 2) a systematic or catastrophic series events that cull the human herd.
The last such event was the Mount Toba volcano eruption about 75,000 years ago is said to have been so catastrophic in its effects on the environment, that it reduced the human population as much as by 50% or more worldwide. I may be inaccurate on the percentage having not looked this up to confirm, but if memory serves, it wiped out a large percentage of the worldwide human population.
Imagine a world where with say 50% of the current world population that was healthier and more intelligent - like the Renaissance period that followed the black plague - ala Dan Brown's Inferno references; would that be so bad if it sustains the human race. Or, if the population continues to grow unchecked and unabated for the next 50 years, global resources declining; what is your vision of the human race at that point?