Biocapacity Deficits and Reserves Biological capacity, or biocapacity, is a way to measure an area's ability to produce biological materials necessary for life, such as food, and to absorb its carbon dioxide emissions. Deficits and reserves are determined by measuring an area's capacity against its ecological footprint—the area required to support an ecosystem's population. Biocapacity Deficit or Reserve, in global hectares NG STAFF SOURCE: GLOBAL FOOTPRINT NETWORK

It may feel like Christmas comes earlier each year, but there’s a less joyful day that really is moving closer on the calendar.

Earth Overshoot Day is the day when—according to estimates—the total combined consumption of all human activity on Earth in a year overtakes the planet’s ability to generate those resources for that year.

How is it measured?

"It’s quite simple,” says Dr. Mathis Wackernagel of the think tank Global Footprint Network. “We look at all the resource demands of humanity that compete for space, like food, fiber, timber, et cetera, then we look at how much area is needed to provide those services and how much productive surface is available."

Here’s his bottom line metaphor. Earth Overshoot Day is like the day you spend more than your salary for a year, only you are all humans and your salary is Earth’s biocapacity.

Ideally, Overshoot Day would come after December 31. It wasn’t too far off in 1970, when it occurred on December 23. But Overshoot Day creep has kicked in ever since. August 13 is the earliest yet—four days ahead of last year’s previous record.

Earth Overshoot Day "Earth overshoot day" marks the day when that year's demand for natural resources exceeds Earth's ability to produce them. Biocapacity reserve Biocapacity deficit NG STAFFSOURCE: GLOBAL FOOTPRINT NETWORK

Overshoot Day doesn’t mean we’ve exhausted our resources for the year. To extend Wackernagel’s metaphor, we’re essentially dipping into savings by using capacity that hasn’t been tapped.

So what happens when we do break open the piggybank? Wackernagel cites struggling fisheries, accumulation of carbon dioxide in the atmosphere, soil erosion and deforestation as some of the consequences.

It’s possible to look at how every country has used its capacity. The United States and China, for instance, overshoot earlier than many other nations, while much of South America has surplus to spare.

This is more complicated than it looks. For example, Singapore exceeds its biocapacity on January 2nd. But "it's just a city,” says Wackernagel, noting that a small, densely populated island doesn’t have much capacity to begin with. Some countries operate within their limits and don’t have overshoot days. That doesn’t mean Wackernagel lets them off the hook.

Country Overshoot Days Countries with small biocapacities, such as islands or desert countries, will reach their respective "country overshoot day" much sooner in the year than countries with larger biocapacities or ecological footprints.

NG STAFF SOURCE: GLOBAL FOOTPRINT NETWORK

"They are extremely resource rich,” he says of one country that isn’t overshooting. “That doesn't mean they use their resources wisely, but that's the privilege of being rich."

Wackernagel doesn’t expect every country to reduce consumption enough to never overshoot. A wiser use of resources for all and surpluses for some would balance out countries like Singapore that may never be able to not overshoot.

Wackernagel says while the “metabolism of the Earth” is accelerating too fast for us now, he sees some positive signs.

"There are some international negotiations, like what's going to happen in Paris,” he says, referring to the UN Conference for Climate Change, where nations will try to reach a global agreement for how to address the environment.