Even as global population growth slows drastically, even as many nations are struggling with natural population declines, even as we live in a time of unbelievable wealth and prosperity, even with all of that, still people are concerned about overpopulation. It is a constant fear for many of us, although, ever since the fizzling of the population bomb, the overpopulation fear has had to move on from a fear of hunger and famine. The green revolution and improved agricultural efficiencies put paid to that.

Indeed, this piece at Vox from Lyman Stone last year, discusses the food production point very well indeed from a US perspective. How many people can the US feed?  First, since a quarter of its food is sent for export, it could support about 25 percent more people just by consuming all its food domestically. If you assume that more people causes more land to move to food production (as farming becomes more profitable) and imports rise and agricultural innovation continues, then the US could support and feed substantially more than 25 percent more people on its current landmass (excluding Greenland).

Translated to the rest of the world, there is huge potential for increased food production elsewhere due to low levels of technological advancement and managerial expertise. And all of this is without even considering that roughly one-third of all food produced worldwide now is wasted in storage, delivery or by consumers.

Perhaps it is not surprising that food scarcity is not driving population panic anymore. Instead, climate change is the reason why we must all worry about too many people. That is why Megan and Harry announced they were only having two children for the sake of the planet before jetting off on private jets four times in 11 days. (Seriously, the more egregious this elite hypocrisy becomes the more I can empathise with the sans culottes.)

But, according to Stone, no amount of population control would achieve the goals of less than two degrees Celsius temperature increase or even the 2.5-2.7 degrees increase committed to by the Paris agreement. One trouble is that as fertility declines, GDP per capita increases as families invest more in human capital for each child. And as GDP per capita increases, so do emissions. The final variable is the emissions per dollar of GDP. However:

“even if we combine lower fertility, more efficient technology and lower economic growth … by the 2030s we are once again overshooting necessary emissions. In other words, this entire exercise is hopeless within current technological constraints.”

The only hope, says Stone, is for a “quantum-leap breakthrough in carbon efficiency – beyond what we observe in even very carbon-efficient economies”. A reduction in fertility by itself won’t make a serious dent in our emissions.  And this is without considering the fact that as people have fewer children, they tend to increase their emissions through consumption – like more vacations overseas (ahem, Megan and Harry!) Thus, while lower fertility will reduce emissions longterm, in the short term lower fertility probably has no net effect. Thus, keeping the US population at 325 million (presumably only achievable through strict anti-immigration laws and draconian population control policies) would produce at best a marginal change in global emission. However, lowering US carbon intensity by about a third (to Germany’s level) would have a bigger impact than “preventing 100 million Americans from existing”.

In short, population control seems like the easy solution to climate change (it sure beats changing our emission-heavy lifestyles!) but in reality it has a marginal impact, certainly when compared with changing carbon intensity per dollar of GDP. And at what cost in human suffering would that marginal impact be bought?

Marcus Roberts is co-editor of Demography is Destiny, MercatorNet's blog on population issues.