Defining Total Environmental Impact: Part 3

According to the World Wildlife Fund's Living Planet Index if you divide all the productive land on earth by 6 billion, the earth's total population, you come up with roughly 1.8 hectares, or 4 1/2 acres. That's the amount of land available to every individual on the planet to meet all their resource needs sustainably. Any more and we are asking the earth to produce more that it can. As you might have guessed, the consumption habits of a typical U.S. resident is close to 5 times that amount, a whopping 24 acres per person! If you want to find out how much land resources your use, take the Ecological Footprint Quiz.

How do different countries compare?

This chart from the WWF Living Planet Report depicts the average per capita land use by country:

What types of impacts are accounted for in the Ecological Footprint model?

The model developed by Redefining Progress and used by The World Wildlife Fund examines six key types of land use -- Energy (or Carbon), Crop, Pasture, Forest (for timber and pulp), Built-up land and Fishery -- used to measure one's environmental footprint. By far the biggest and most consequential impact is the Carbon Footprint.

What is a Carbon Footprint?

The carbon footprint is the area of biomass - typically forest land - that is needed to capture the CO2 or carbon dioxide generated from burning fossil fuels -- from driving your car and heating your home to transporting those bottles of Fiji water to your local grocery store. What absorbs all this CO2? Several studies have shown that the ocean absorbs roughly 31% of our CO2, leaving an additional 69% to be absorbed by trees and other terrestrial biomass. This works out to approximately 0.95 metric tons of Carbon per hectare per year, or 3100 lbs of CO2 per year (data sources).

What is the relative weighting of different types of impacts for the average American?

The approximate ratio of land resources utilized in EVO's Total Environmental Impact model (for the average American) is depicted at left. These numbers are derived from data presented by Redefining Progress (in uncalibrated units of land use) for 6 consumption categories -- Food, Transportation, Housing, Goods, Services and Waste.

Each of the six categories looks at specific products and services and the bio-productive land required to produce them -- including the land required to both source the materials and subsume the wastes associated with each product. The result is an ecological footprint that sums all impacts for the products and services you use. This model is very useful because it allows us to get a clear picture of how any type of consumption – say our habit of eating red meat – effects our overall ecological footprint.

The Ecological Footprint is a truly comprehensive model. The Global Footprint Network just received a generous grant from the Skoll Foundation to update the Ecological Footprint model using recent data and more precise calculation methods, which will give us an extremely accurate representation of our specific environmental impacts. In the meantime, the current Ecological Footprint provides a helpful snapshot of our CO2 and land use.

Since this model measures in increments of land area, it does not account for other significant environmental factors such as water consumption, water pollution, and air pollution. To help us gauge those impacts, we turn to the Union of Concerned Scientists.