Big footprints on our planet
If every human on the planet (there are 6 billion of you) wanted to live like most North Americans, there simply wouldn't be enough resources. If every human on Earth lived like the average Canadian (for example), you'd need at least three Earths to provide all your materials and energy. This is where you might like to think about the idea of 'ecological footprints'. A 'footprint' is the amount of land each person needs to take from Nature to support her or his consumption of materials - like food, energy, wood and so on. [1]

Canada is one of the world's richest countries with the highest 'standard of living' = highest level of gobbling resources. The ecological footprint of an average Canadian adds up to an area about the size of three city blocks (4.8 hectares of land - nearly 12 acres). Unfortunately, the actual productive land available to each person on the planet today is, on average, about one city block (1.6 hectares, less than 4 acres)... one third of the area which each Canadian is now using.[1] So there's what's called an 'ecological deficit' - like drawing more money out of a bank than you have so you're really 'borrowing' from someone else. [2]

For more about this, visit the Gobar Times Big Foot - for kids.
[1] International Institute for Sustainable Development
[2] Find out about 'ecological deficits' and 'sustainability gaps' here