Some scientific issues are indeed very complicated, and in a free society people would rely on competing scientific institutions (ex. hired by insurance companies) to help them understand risk factors that could affect them. This particular issue, however, just isn't that complex.
If you actually look at the numbers, it's amazing how far "we" (meaning the human civilization) could increase sustainable food production - even without increasing agricultural space OR agricultural productivity! What does that leave? Eating habits.
A huge fraction of agricultural resources are being wasted by passing them through an animal's body prior to human consumption, with as much as 95% of the nutrients turning into environmentally hazardous byproducts rather than food. Most people in the "first world" eat huge portions of meat that provide more protein than their body can even utilize, leading to obesity and ever-large appetites. A lot of agricultural resources are wasted on producing unhealthy caffeine beverages, processed foods, alcohol, tobacco, etc. If everyone ate a healthy ~2000-calorie diet that centered on fresh vegetables and only drank water, then the same agricultural space / productivity we have today would feed ~20-40 billion human beings, and those people would be a lot healthier and live longer as well!
Of course most people would not want to make those changes, but in a freer society they would be more encouraged to do so through price and insurance incentives. The biggest enemy of agricultural efficiency is government, which
subsidizes and propagandizes meat consumption, and discourages preventative health measures like healthy eating through socialized medicine. A lot of people would go vegan if it meant large savings off their health insurance. If artificially extracted hormone-induced cow puss (aka "milk") cost $30/gallon, a lot more people would drink soy milk instead! Governments are also guilty of mismanaging vast amounts of farmland with economically retarded programs like subsidy of bio-fuels. Socialist governments of the "third world" are keeping their farmers in an artificial state of backwardness. And of course governments stifle the agricultural accessibility of some of the most efficient plants, like hemp.
The fertility rates might have already reached the break-even point - the official global estimate of
~2.5 children per woman is misleading, because some indicators are lagging. More importantly, most of the world's children are born in extremely poor high-mortality countries where 3 or even 4 children may be needed to assure a steady population. If we didn't reach that point already, we undoubtedly will in the next couple of decades. Population growth will continue "running on fumes" for a few decades beyond that, due to demographic momentum and increases in longevity, but the human population will inevitably age and then begin to decline within the next ~30 years.
What happened in Iran (1.89 children per woman and falling, in spite of radical Islam) will soon happen in Afghanistan. What happened in Lebanon (~1.7 children per woman) will happen in Saudi Arabia. What happened in Trinidad and Tobago, Maldives, and Mauritius will happen in all of Africa and India as well. Etc. And eventually the rates in those countries will resemble those of South Korea and Italy (even though both currently still have religious people that have families). As the world becomes more educated, urbanized, and secular, people simply stop having enough children. We're headed for a civilization where population is cut in half with every generation - which leads to an inevitable economic collapse!
Even if by some miracle we managed to maintain the current ~2.5 fertility rate, while curing AIDS and otherwise reducing "third world" mortality to "first world" levels, it would still take us about ten long generations to exceed the aforementioned carrying capacity, which we can achieve by doing nothing more than eating a healthy diet. But of course agricultural productivity will continue to increase, with today's high-tech greenhouses and hydroponics already producing as much as
100 times more food per acre than low-tech farming that is still employed in many parts of the world today. What will happen in the next 300 years is speculative, but the craziest assumption of all is that technology will somehow simply stand still!
So overpopulation is a total non-issue, a crazy fantasy, like of a person who refuses to leave a rapidly burning house because it's raining outside and he might catch a cold!
Edited by Alex Libman, 11 September 2011 - 07:05 PM.