Human Population: The Mother of Them All?

Bluey here,

I've been thinking about something that seems plain enough to me but hasn't been talked about much down on my surface by humans; at least not to my knowledge... I haven't discussed it with my GP yet, but I think it's important to bring up.

Why is it that human population is not a Planetary Boundary? Moreover, why is it not the Planetary Boundary?!

I went searching for the stirrings of an answer. This recent article acknowledged that human population was the 'elephant in the room'—and even mentioned GP Steffen—but failed to discuss its planetary boundary credentials. Though it did point to a 2012 UNEP report, called One Planet, How Many People? A Review of Earth’s Carrying Capacity. I found it similarly inconclusive, however an 8 billion figure emerged as an approximate 'carrying capacity'.

'Carrying Capacity': 65 estimates (Source: UNEP)

I must admit, when I read that one study put my 'carrying capacity' at 1,024 billion, I did have some immediate concerns around its veracity. However, the report was able to maintain its integrity, admitting that agreeing upon "a static ceiling for sustainable human population seems destined to uncertainty", and blaming some of the more 'exponential' studies on methodology and assumption differences.

Historical World Population (Source: UNEP)

Eventually, I found what I was looking for. A paper by Population Matters. Human population was overtly mentioned in the same sentence as planetary boundaries:

"Although population is not one of the nine planetary boundaries, the rising level of human population undermines our efforts to limit human development to the above-mentioned nine planetary boundaries."

I think undermines should be replaced with sabotages personally. According to last year's report by the UN, population is growing at 1.18% per year, expected to tip 10 billion just after 2050 and 11 billion 40 years later. My Africa region is expected to witness the bulk of growth, while my Europe and even my China regions are expected to decline. India will soon surpass China as my most populous region!

Lastly, let's touch on the other 'elephant in the room' that's emerged: human consumption. Mathis Wackernagel and colleagues think humans began exceeding my regenerating capacity in 1980 and now use 1.5 of me! While their concept of a human 'ecological footprint' has been contested, it's another very interesting perspective which I plan to look into in the future.

One thing's for sure, I will be pressing GP Steffen about why human population—and it's partner in crime, human consumption—has not been made a PB at our next appointment.

Yours for awhile,
Bluey