On July 29, we cross an alarming threshold. This date marks Earth Overshoot Day, the point each year at which humanity starts to consume the worlds natural resources faster than they can be replenished.

Its taken us only 209 days to burn through a years worth of resources everything from food and timber to land and carbon. We are using up nature 1.75 times faster than it can be replenished. To do this sustainably, we would need the resources of 1.75 Earths.

These latest figures come from Global Footprint Network, an international nonprofit that calculates our annual ecological budget and the date at which we exceed it. Once we bust through this budget, we start devouring resources at an unsustainable rate.

Its a pyramid scheme, said Mathis Wackernagel, CEO and founder of Global Footprint Network. It depends on using more and more from the future to pay for the present.

Its like being in financial debt, only much harder to recover. Theres nothing to kickstart the economy if we overuse our resources, he said, because every economic activity depends on natural capital, and without that, its not going to work.

The burden of this ecological debt is getting heavier. We started overconsuming resources back in the 1970s, and since then its gotten progressively worse. Over the last 20 years, Earth Overshoot Day has crept forward by more than two months. And this year, it falls on the earliest date yet.