In the past forty years, the human population has gone from 3.7 billion in 1970 to the current estimate of 6.8 billion. In year 1000, world population was estimated to be only 265 million. At the current rate of growth, world human population is expected to exceed 8 billion by 2025 and 10 billion by 2061.
This phenomenal increase in population has been due to a combination of factors. Foremost among them is the introduction of modern sanitation and hygiene practices. More babies (and mothers) survive birth and childhood, and are growing up to have babies of their own. Separating sewage water from drinking water, and washing hands with soap or other grinding agents, has made a tremendous difference in human health and longevity. In Roman times, human life expectancy was about 22-24 years, largely as a result of high infant mortality. By 1900, this had increased to 30 years, and by 1985 to over 60 years. Most of these gains are due to the rapid decline in infant mortality, which went from 152 deaths per 1000 live births in 1950 to only 47 in 2010.
There are serious questions of whether or not the Earth can support a population this high. Given the way that wild fish stocks are being depleted, the depletion of oil reserves, global climate change, and a host of other human-caused problems, it is becoming increasingly clear that the Earth cannot sustainably carry the current population of 6.8 billion, let alone the 10 billion forecast.
Estimates for a global sustainable population are between 2.7 and 5.1 billion people. From this alone it becomes clear that the global population needs to be reduced. Even at that, though, becoming sustainable requires the high-income countries to reduce their ecological footprint by up to 60%. To attain these sustainable levels, the world needs to experience negative population growth. There aren’t too many ways to do that, short of war or disease. Or having a lot fewer babies.
China’s “one-baby-per-family” rule, while widely unpopular, may have to become the norm for countries the world over. This type of policy is not likely to be popular, and would require either widespread public education and acceptance, or imposition from a totalitarian state. The first case would be by far the most preferable, to give people the opportunity to see the necessity of such a measure, and voluntarily adopt it. The second case becomes more likely as population-related crises begin to mount.
In an ecological sense, humanity is a super-predator, consuming everything with lethal efficiency. The overpopulation of a super-predator means huge problems for an ecosystem. The only solution is bring the numbers down. If we can’t do it ourselves, then nature is likely to do it for us. It would be better to institute policies that would bring human populations down to a sustainable level in a controlled way, rather than having disease, famine, or pestilence do so in a sudden, catastrophic manner.