We consume resources faster than nature's rate of productivity, and we produce waste faster than nature can absorb it. Simply put, ecological sustainability requires the preservation of nature's productivity. We need to view our consumption on a sustainable level. To give a numerical value to our present consumption level and its effect on the environment is difficult. It is difficult to use this definition for human beings because of the global economy.
People consume resources from all over the world.
In contrast to animals, people's consumption is not limited by their biological needs. While animals consume little else but their food, the bulk of people's material consumption consists of non-food items such as energy. For the average Canadian, the consumption measured in energy adds up to over 850,000 kilojoules per day. The following activity will allow students to estimate the size of their own footprints. It does not measure the complete footprint, but only that part of the footprint that is created by energy.