Mathis Wackernagel and William Rees, two community planners at the University of British Columbia in Canada, developed an innovative way to answer this question in their 1996 book Our Ecological Footprint. Their statistical measure — what they call an ecological footprint — reveals the impact each country has on the world’s resources. Not surprisingly, "modern" economies, such as the United States, have the largest ecological footprints. These economies require far more land, energy, and water, and emit much more of the carbon dioxide that is so harmful to human health and the atmosphere, than do the poorer nations, even though poor nations are home to most of the world’s population.

The ecological footprint measures the resources consumed by a community or a nation, whether they come from the community’s backyard or from around the globe. Earlier studies had determined a community or nation’s "carrying capacity" — the number of people a society can support before it loses its ability to support itself. Wackernagel and Rees’ innovation adds in richer countries’ use of trade and technology to import resources they don’t possess.

Wackernagel and Rees ask how many hectares or acres are needed per person to support a nation’s consumption of food, housing, transportation, consumer goods, and services. They calculate how much fossil energy use, land degradation, and garden, crop, pasture, and forest space it takes to produce all that consumers buy.

For example, Wackernagel and Rees determined that Vancouver, British Columbia, their home, runs a large "ecological deficit" with the rest of the world. As they calculate it, Vancouver needs an area 19 times larger than its 4,000 square kilometers to support the food production, forestry products, and energy consumption of the region.

Based on 1991 figures, the U.S. ecological footprint was 5.1 hectares per person, or over 12.5 acres. In contrast, each resident of India requires 0.4 hectares or just over two acres to maintain his or her livelihood per year (see table).

The implications of these ecological footprints for world development are profoundly disturbing. For instance, for everyone on earth to enjoy the ecological standards of average residents in Canada and the U.S., an additional planet or two would be necessary. And while the material wealth of people in the rich countries increased during the 20th century, the First World used up so much space and resources in the process that little is left for poor countries hoping to obtain a similar standard of living. To sustain these inequitable ecological footprints, most rich countries run large ecological deficits with the rest of the world.

If the ecological marks left by all the world’s people are to be distributed more equitably, then Americans, Canadians and other residents of wealthy countries are going to have to change their habits radically. A modest first step in that direction would be to require that the industries and governments that drive the world economy include an analysis of their impacts on the environment, or ecological footprint, in their economic forecasts.

    — By David Holtzman