1. A growing debate

2. Population growth: Environmental disaster?

3. Contrarians speak

Calling all consumers! Does affluence breed environmental destruction?

The global "ecological footprint" is already larger than our planet. Translation: We're spending our natural capital, not living off the interest. Data source: World Wide Fund for Nature

Regions with serious soil degradation. Image from United Nations Environment Program

A majority of U.S. immigrants come from the Americas, primarily Mexico.

High on the hog
Why worry about the environmental impact of a growing U.S. population? Because there are so many of us -- and we use so much stuff, is the short answer. In the United States, P * A are both growing, and as a result, so is I -- environmental impact.

When it comes to the rate of consumption, Americans excel, says William Rees, at the Fisheries Center at the University of British Columbia.

Rees invented the "ecological footprint," which, he says, "measures the total ecosystem area needed to sustain your life, in terms of how much land is needed to grow your food, produce your energy, and absorb the carbon dioxide created by your actions, direct and indirect. (When a generator burns coal to make electricity, it dumps carbon dioxide into the atmosphere. Green plants remove this greenhouse gas from the air, but many acres of plants are needed to remove the carbon dioxide made by one American.)

Everything we do, whether it's burn gasoline in oversize personal transportation units, over-wrap products in nuclear-bomb-proof plastic, grow food, smelt metal, saw wood, pump freshwater, make junk mail, or pave highways, should show up in our ecological footprint, Rees says. "It's our total demand to ecological goods and services," he says, measured in the area of productive ecosystems -- farms, forests, swamps -- needed to provide those goods and services.

The ecological footprint is one way to interpret the impact term in Ehrlich's famous equation (Impact = Population * Affluence * Technology), and it says what we already know. Resource-hogging countries place huge demands on the Earth. "Countries like Canada, the U.S. and Australia have enormous ecological footprints," Rees says, about 8 to 10 hectares per person. "Each of us in North America needs 20 to 25 acres of land to produce our food and assimilate all our wastes; it's a fairly substantial chunk of territory."

Call that Canadian understatement. The world ecological footprint already exceeds the world's supply of productive land, Rees argues. The amount of productive land comes to 11 to 12 billion hectares. With 6 billion people, if it were a totally equitable planet, we'd each get 5 acres (2 hectares) each."

Instead, we are using the equivalent of 1.2 planets now. Americans and Canadians suck down 20 to 25 acres worth of land, so if everyone was to live Norte-Americano-style, he says, we'd need four or five planet Earths.

So how do we get by? "By using up the stock, depleting the fisheries, depleting forests, drawing down fresh water, eroding soil," he says. All the grim statistics on specific ecological declines show what the ecological footprint suggests: We have overshot the long-term carrying capacity of the planet. We are consuming the planet.

In short, I is sky-high.

National eco-debt
Population growth also threatens a less measurable value -- wilderness -- whose preservation is a key goal of the Sierra Club. Here, the pressures are more obvious, even in a single lifetime, says Lamm. "When I moved to Northern California in 1958 to go to law school, there were 10 or 12 million people, and it was paradise. I'd climb a mountain and there were no other people. You still had a place to get away from fumes, smoke, clutter. Now it's 35 million, and heading toward 50 million people. To say that's not an environmental issue..."

Lamm calls momentum the worst part of population growth. "People don't realize that we will probably double the size of America, just with the momentum we already have. There's a braking distance to population growth; just like a car, it does not stop suddenly. The car I drove to work puts stuff in the atmosphere that will not have its full impact on global warming for 50 to 70 years." By the time we recognize what we are doing, he cautions, "it may be too late."

Big foot print
To Rees, the huge U.S. footprint will only increase as population grows, fueled in large part by immigrants. "Among highly developed countries, the U.S. has the highest growth rate. So here we have this country with about the largest ecological footprint on the planet, with a very large population growth rate, which then increases the total ecological footprint."

Population growth has global and local affects. Let's take a pet Why Files concern: What's going to fill our feedbags? As farm fields are paved and built over, where will farmers farm? The Sierra Club's anti-sprawl campaign says sprawl is driven by both population growth and poor planning. In 213 urban areas, the group summarizes, "between 1960 and 1990 population increased from 95 million to 140 million (47 percent) while urbanized land increased from 25,000 square miles to 51,000 square miles (107 percent)."

As farmland becomes subdivisions, where we gonna grow our food?

As cities sprawl, farmland gets gobbled, says Pimentel, the agricultural scientist. "I think we should be protecting more agricultural land, this is where we get 99.7 percent of our food, in the U.S. and the world. ... I'm not saying it's a crisis yet, but once you have covered the land with highways or buildings, it's lost."

We could go on, citing arguments by those who say that more people need more resources, an equation that's especially true of the United States. After all, if Impact = Population * Affluence * Technology, both population and affluence are booming in the United States. And while technology could reduce the multiplier effect of P and T, it's not done so yet.

So it's a slam dunk: population growth = environmental destruction. Case closed?

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