The population conundrum

Too often, it seems, matters of population are overlooked in discussions of global sustainability. And this is true, despite some rather obvious points: A world of, say, 5 billion people is more likely to be sustainable than one of 10 billion; and a world of 1 billion is likely more sustainable still....

Currently the Earth is at roughly 7.7 billion, heading to 9.5 billion by 2050, and perhaps to 11 or 12 billion by 2100. Each year about 135 million babies are born; if we subtract the 55 million annual deaths, we get an annual growth rate of 80 million—or around 220,000 more humans every day. Every one of these people needs clothing, shelter, food; they produce waste; they buy things and discard things; and they compete for space on this planet with all other animal and plant life... This is not a recipe for long-term sustainability.

But it’s not just human numbers, as we know. It also depends on how much each person produces and consumes—their standard of living, and specifically how much of the Earth’s resources each requires, on an on-going basis, to support their lifestyle. This aspect has been factored into the ecological footprint: a measure of land-area equivalent, per person, that represents the average resource use of each person in a given nation....

... the US has around 810 million hectares [about 2 billion acres] of land. And yet, as we see above, the total footprint of the US is about 2,700 million hectares. Hence they are over-using land by a factor of 3.3; in other words, Americans use more than three times as much land as they have....

How is this possible? Partly by overtaxing their land, and partly via that economic practice known as globalization....

Obviously, this is an unsustainable situation. It is not a global model. Every nation cannot overstep its consumption; there is only one Earth, after all....

Much less than the 810 million ha can used, sustainably, in the long-run....

How much would be fair and yet still get the job done? Here’s one proposal: 50/50...

Prominent biologist E. O. Wilson has notably defended a similar figure, in his proposal of “half-Earth.” See his 2016 book of the same name, and the organization he established online at Half Earth Project....

All this boils down to two essential principles of global sustainability:

1. Each nation should set aside half of its land area, as wilderness or protected land.
    
2. Each nation should adjust its population and consumption to live on the other half.

Harder would be to reconfigure American society to live on the other 400 million ha. It has three options: (1) reduce population, (2) reduce per capita footprint, or (3) some combination of the two. Let’s say Americans want to continue to live at their luxury level of 8.1 ha per person. No problem—they just need to have less people. A lot less people. The math is straightforward: 400 million ha divided by 8.1 allows just 50 million people....

Furthermore, this suggests the need to set national and global targets for both population and footprint. Both are currently rising: global footprint at 2.1% per year, and global population at 1.0% per year....