Humanity's Tipping Point

I've just finished reading a(nother) fantasy book--Midnighters #3: Blue Noon--where one of the characters, Rex, considers the potential end of the world. For humans at least:

In the darkling part of his mind, Rex thought for a moment that perhaps this wasn't such a bad thing. Without predators to cull the herd, humanity had spread across the earth unchecked, crowding the planet beyond its resources, prideful and arrogant.
Maybe one night a year of being hunted would do them good.

Though one night a year may not seem like a lot, in this book it equates to thousands of deaths, if not millions. Granted, out of 7+ billion people, that's a pretty small number, but still.

Anyway, I know that end-of-world stories, or at least end-of-humanity stories have been quite popular lately (with zombies only being one aspect of them), and I think they do bring up an interesting point: considering we're at the top of the food chain (with nothing to cull our population growth), then how long can we continue on this path before we've outgrown our environment?

Population growth is currently at 1.14% per year. Granted, the rate has supposedly started to decline again (thanks to developed countries), but just over the 20th century the world population grew 264%, from 1.65 billion to 6 billion. Now that's not chump change.

So, since as Harvard University sociobiologist put it, "[t]he constraints of the biosphere are fixed," how many humans can our little Earth sustain? About 9 to 10 billion (according to some scientists). That's not much higher than our current level and, according to predictions, is a number that should be hit between 2040 and 2062. So in 25 to 47 years. Or relatively soon and, in most people's case, our lifetime.

Exciting news, isn't it?

So what are we to expect then? Short water supply (better start stocking up on those bottles!), short food supply (makes us feel bad about wasting 1.3 billion tonnes of food every year, doesn't it?), To make the picture a little bleaker, the 10 billion sustainability mark is assuming everyone becomes a grass-eater (vegans FTW!), so a more realistic picture would bring down that mark... Although, considering the current specie extinction rate is 1,000 to 10,000 times higher than the natural extinction rate (aka background extinction rate: rate of extinction without human involvement), that means between 200-2,000 (on the low end) or 10,000 to 100,000 (on the higher end) species are becoming extinct, I have a feeling this constrains our biosphere parameters even further. Robot bees just aren't going to be enough to make a difference...

So all you zombie/apocalypse fan boys and girls there might get to experience survival scenarios (who knows how people would react in such a world?). As for everyone else, well, let's hope we figure something out, and soon. (I'm totally for colonizing Mars, btw!)

In the meantime, I'm going to enjoy my time with my family and friends that much more and appreciate my Christmas dinner fully (with no wastage!).

UPDATE - 2015.01.22:
Just read this article about humanity tipping the earth's ecological and weather patterns into unsafe zones, with already two large "dead zones" reported, and more to come if we keep up with our current activities (especially the production of the chemicals phosphorus and nitrogen). The scientists in charge of the study stated that we've hit 4 out of the 9 "safe operating space" boundaries, getting closer and closer to the point of no return where life won't be as friendly as it has been up until now...

Sources:
Live Science - How Many People Can Earth Support?
World Population Clock (with amazing charts!)
UNEP - Food Waste Facts
WWF - How Many Species Are We Losing?
Center For Biological Diversity - The Extinction Crisis
Robobees