World population is expected to reach nine billion by 2050. To put that into perspective, the current population of 7.6 billion humans outnumbers every other species of land-based vertebrate on the planet with the exception of the domesticated chicken at 18.6 billion. The brown rat may also outnumber humans, but with no corporate sponsor, such as Tyson, so there's no incentive to count it.
Humans are not only more numerous, but with an aggregate weight of 350 million tons, we rank in the top ten species with the highest biomass. Only cattle outweigh humans at 520 million aggregate tons.
If the world is indeed an ecological pyramid with primary producers, such as photosynthetic organisms, at its base, then it stands to reason an apex predator would represent a much smaller fraction. Humans have removed this pyramid’s capstone and somehow balanced another pyramid on top. Paul Ehrlich, author of The Population Bomb, stated in a 2012 Guardian interview that “to guarantee the minimal physical ingredients of a decent life to everyone—would be 1.5 to two billion people.”
According to data compiled by the Global Footprint Network, the amount of arable land needed to support each person, 2.71 hectares, surpassed the amount available (about five billion hectares) in the 1960s, when the world population reached three billion.
By reducing the population to sustainable levels, we reduce the risk of extinction or at least worldwide calamity. It is the old “eggs in one basket” argument. Dense concentrations of any species tend to fall prey to airborne pathogens such as influenza. Modern air travel only compounds the risk of a global pandemic.
And then there’s climate change, which seems to be intimately tied to the rapid rise in population over the last 200 years. When graphed and compared, increases in total population, atmospheric carbon levels, and global average temperature look almost identical.
A recent study in Environmental Research Letters examined “green” lifestyle choices and calculated how much carbon dioxide each activity prevented. Having one fewer child resulted in a yearly savings of 58.6 tons. Living car-free prevented a mere 2.4 tons.
While the rate of population increase has been falling over the past few decades, it has yet to reach equilibrium. Some countries, such as Japan, are experiencing negative population growth. One of the most significant factors driving this trend is the link between educational opportunities for women and the number of children conceived over a lifetime. Although, this effect, in and of itself, is not enough to halt growth, as college-educated women still average 2.1 births.
China's “One Child” policy attempted to address overpopulation. The idea was that couples should limit themselves to bearing only one child to prevent population growth from outstripping available resources.
The policy was instituted in 1979 with limited success. Draconian enforcement, such as forced abortions and sterilizations, were often used. An uptick in female infanticide occurred due to the preference for male children. The policy was altered in 2015 to a two-child limit as party leaders realized that one worker’s taxes could not support the retirement of two parents and as many as four grandparents.
A one-child movement could dramatically reduce the human footprint. The US and other countries reward couples with a tax exemption for each dependent child. If this policy were reversed, so that each child after the first resulted in a progressively higher tax penalty, individual incentive to limit procreation could be generated without resorting to China’s missteps.
The penalty could reflect the cost of scrubbing the extra carbon dioxide and earmarked for environmental restoration. A lifelong tax break could be offered to those who choose surgical birth control. To avoid using such a policy for racist purposes (as racists have tended to support population control as a form of eugenics), nations could exempt minority populations.
Access and attitudes to contraceptives and reproductive health services would also have to change in some countries and cultures. Opposition is sure to come from religious groups as well as business and government. Without a growing population, public and private coffers tend to stagnate or shrink. But whether this idea catches on or not, revenue streams are sure to be disrupted in the very near future as automation reduces the need for blue- and white-collar workers. The issue of how to provide for both retired and displaced workers will need to be addressed at some point.
No other action we can take would have as much environmental benefit. The 2015 Paris climate accord, dealing with natural disasters and disease and reducing regional tensions that lead to armed conflicts, would be much easier to achieve if there were a gradual reduction in the number of humans on the planet.
David Glenn is a sentient being with a bipedal Simian body-type. His current location is on the North American continent a few hundred meters or so from the world's largest freshwater lake.