For the past several years, as the days of summer start getting just enough shorter for you to realize that fall is coming, I've received an email announcing that Earth Overshoot Day has arrived. Every year it comes a little bit earlier—which is the essence of the problem.
Calculated by the folks at the Global Footprint Network, Earth Overshoot Day is a best estimate of when we collectively—this vast human civilization that's ever growing in numbers and appetite for things—begins to use more of the planet's resources than can be annually regenerated. We go into ecological overshoot.
In absolute terms, on vast geologic timescales, it's too much to say that we're permanently depleting the planet's ability to support life, but on a human scale we're doing just that. Put in the language of ecological economics, we're depleting natural capital.
This year Earth Overshoot Day arrived on August 20th, two days earlier than it did in 2012. In 2011, the Day arrived on September 27th, with the vast jump between those two years representing differences in calculation rather than a directly comparable changes in resource consumption. Quantifying this, all of human civilization consumes 1.5 Earth's worth of resources. We need another half-planet to support us sustainably into the future. By 2050, on our current trajectory, we'll need another entire planet.
There's a natural concern with the concept: It is difficult to quantify worldwide consumption and compare it to world ecological productivity. The 1.5 Earths figure is for all nations, but there are wide discrepancies in consumption. China is currently has the world's largest total ecological footprint, due to its world-leading population, but even as such, on a per capita basis its impact, while still unsustainable, is far lower.
If every person on the planet lived like the average Chinese person, we'd need 1.2 planets worth of natural resources, but that's still an average of China's very wide spread. If every person lived like the average American, we'd need four planets. If everyone lived like the average Qatari, we'd need seven.
Obviously this won't happen. Regional ecological collapse or conflict will occur (and already has) before the whole world is spent. A glimpse of how the conflict may begin can be seen in another facet of GFN's calculations: Which nations are ecological debtors or creditors, that is which nations are consuming more resources than can be supplied within their borders.
China currently consumes 2.5 China's worth of resources, import-dependent Japan consumes 7.1 Japans, the resource-rich US consumes 1.9 United States, and India consumes 1.8 Indias. The additional resources needed for each of these nations to support their current lifestyles and consumption has to come from outside their territories.
Regardless, the endgame of our current resource will result in humanity changing its ways, voluntarily or involuntarily. If total resource consumption were within the ability of the planet to annually regenerate the pressure would be reduced. While not eliminating resource conflict—a constant source of strife throughout human history, probably more than any other factor—living within the carrying capacity of the planet would ease this potential for conflict considerably.
GFN points out that half a century ago all of humanity consumed roughly two-thirds of the available natural resources on the planet. While on a regional basis there were collapses of a particular resource going back millennia—sometimes resulting in the destruction of a particular local or regional industry, sometimes a regional culture—the Earth as a whole was more able to regenerate what was consumed every year. The difference now is the collapse could cover a much wider swath of the world.