Global Footprint Network (GFN), a California-based environmental research organization assesses Earth Overshoot Day each year. They calculate humanity currently uses more than 1.5 times the Earth's regenerative capacity in a year.

"Overshoot can be thought of as living off your credit card. Humanity is living off its ecological credit card," explains Global Footprint Network Associate Director Susan Burns.

Throughout most of history, humanity has stayed within the planet's carrying capacity. But since the mid 1970's, we've been using more resources than can be replenished, meaning we keep going deeper and deeper into the hole.

Each year, "Earth Overshoot Day" comes sooner. In 1992 GFN estimated that Earth Overshoot Day fell on October 21, by 2002 it was October 3, and by 2009 it was September 25. If current trends continue unchanged, we are on track to require the annual resources of two planets well before 2050.

"Our ecological overspending has become a vicious cycle, in which we draw down more and more principal at the same time our level of consumption, or "spending," grows. The social and economic costs could be staggering," said Dr. Mathis Wackernagel, Global Footprint Network President.