Of course, we only have one Earth. The fact that we are using (or "spending" natural capital) faster than it can replenish is similar to continually making purchases that exceed income. This gap between demand and supply -- known as ecological overshoot -- has grown steadily each year. Global Footprint Network's most recent data show it takes one year and five months to generate the ecological services (production of resources and absorption of CO2) humanity requires in one year.

Climate change – a result of carbon being emitted faster than it can be reabsorbed by the forests and seas – is the most obvious and arguably pressing result. But there are others: shrinking forests, species loss, fisheries collapse and water pollution, to name a few.