Congratulations! You have recently resolved to reduce the impact you and your family are having on the planet’s ecosystems. You’ll consume less, reuse and recycle more, and generally live more sustainably.
But how can you know what your actual impact is? Or how much you should reduce it to make a difference by beginning to balance your consumption with the rest of humanity’s, and your needs with nature’s ability to provide for them? Can you make a reasonable estimate of what your consumption of resources means to the planet?
One way to answer those questions is to calculate your “ecological footprint,” the amount of the planet’s ecologically productive land needed to provide for your resource consumption and assimilate your wastes.
By expressing the impact of your activities in terms of the productive acreage of farmlands, grasslands, wetlands and forests needed to support them, you can calculate how much of the Earth’s renewable resources you are using. Thus you can see how your footprint relates, proportionately, to those of your fellow humans in terms of its share of available resources. (Difficulties in correlating ocean surface area with productivity precludes oceans from footprint calculations.)
Borrowing an analogy from the readable and delightfully illustrated book Our Ecological Footprint by Mathis Wackernagel and William Rees helps us understand the ecological footprint concept. Imagine that your house and yard are covered with an impenetrable dome that prevents the flow of air, water, food and materials into or out of your property: How long do you think you and your family could live?
The answer is something like a couple of days at most, because you would breathe in the oxygen inside in the dome, change it to carbon dioxide and suffocate. If you had lush vegetation on your property you would last a little longer because it would convert some of the carbon dioxide you exhaled into oxygen. But even if the dome let oxygen in and carbon dioxide out, you would still perish soon because you would use up your water and food reserves.
Now imagine the dome to be larger. How large would it have to be to support you and your family at your current rate of consumption? That acreage, roughly, is the size of your ecological footprint.
Fortunately, you can calculate your footprint without building a dome. By using relatively simple formulas explained in Our Ecological Footprint and taking surveys at one or more of the many websites that feature ecological footprint “calculators,” you can get a pretty good idea of your resource use and where it fits into the big picture.
Since your overall footprint is calculated as the sum of individual components – CO2 emissions, paper and cloth consumption, fresh water withdrawal and so on – you can decide which items to reduce to have the greatest effect. If, for example, you have a small house and don’t drive much, you might find that reducing your water use is the key to reducing your overall footprint.
Distressingly, humanity’s total footprint is larger than the regenerative capacity of all the planet’s ecosystems combined: It would take an area equal to 1½ Earths to continue to support us. We are living, temporarily, on the surplus ecological productivity of the recent past, but we can’t continue doing so for long.
Unsurprisingly, the average American’s ecological footprint is large – the largest in the world. We each need about 13 acres of ecologically productive land to support our lifestyle, compared with about 4½ acres for the average global citizen.
Clearly, most of us can do a lot to reduce our footprints at our ecological house.
Philip S. Wenz, who grew up in Durango and Boulder, now lives in Corvallis, Ore., where he teaches and writes about environmental issues. Reach him via e-mail through his website, www.your-ecological-house.com.
