The Environmental Weight of 300 Million Americans

PORTLAND, ORE. -- A flotilla of 100 fishing boats, rafts, and kayaks crossed the Willamette River to a downtown park in Portland, Ore., the other evening to rally for the Pacific Northwest's reigning icon: wild salmon, now plummeting toward extinction due to development across much of the Columbia River basin.

It was a typical event for a "green" city that has one of the best records in the United States for recycling, reducing greenhouse-gas emissions, using alternative energy, and providing public transportation and bike paths.

But Portland's amenities -- its natural setting along the Willamette River and its youthful techie vibe -- are drawing a surge of new people, threatening to erode the very qualities that drew people here in the first place. As the US approaches 300 million people, that's the story of the nation as well.

In many ways, Americans have mitigated the impact of their increasing presence on the land. Since reaching the 200 million mark back in 1967, they have cut emissions of major air pollutants, banned certain harmful pesticides, and overseen the rebound of several endangered species. Despite using more resources and creating more waste, they've become more energy efficient.

The danger, experts say, is that the US may simply have postponed the day of reckoning. Major environmental problems remain, and some are getting worse -- all of them in one way or another connected to US population growth, which is expected to hit 400 million around midcentury. Some experts put the average American's "ecological footprint" -- the amount of land and water needed to support an individual and absorb his or her waste -- at 24 acres. By that calculation, the long-term "carrying capacity" of the US would sustain less than half of the nation's current population.

"The US is the only industrialized nation in the world experiencing significant population growth," says Vicky Markham, of the Center for Environment and Population, a nonprofit research and advocacy organization in New Canaan, Conn. "That, combined with America's high rates of resource consumption, results in the largest ... environmental impact [of any nation] in the world." The boomer challenge

The changing nature of the population also has environmental consequences.

"Today's baby boomers -- 26 percent of the population -- are the largest, wealthiest, highest resource-consuming of that age group ever in the nation's history, and they have unprecedented environmental impact," says Ms. Markham.

The generation's preference for bigger houses and bigger cars -- and the proliferation of them -- are gobbling up more resources and creating more pollution, according to a recent study by the Center for Environment and Population. For example:

• Land is being converted for development at about twice the rate of population growth. When housing, shopping, schools, roads, and other uses are added up, each American effectively occupies 20 percent more developed land than he or she did 20 years ago.

• Nearly 3,000 acres of farmland are converted to nonagricultural uses daily..

• Each American produces about five pounds of trash daily, up from less than three pounds in 1960.

• While the US is noted for its wide open spaces, more than half of all Americans live within 50 miles of the coasts where population density and its environmental impact are increasing.

That concentration poses special challenges for areas near the coast, like Portland, where land is rapidly being gobbled up. The city's population, which is now a bit over half a million, is fairly stable. But surrounding population pressures are great. The metropolitan area grew about 30 percent during the 1990s to just over 2 million. It's projected to grow to 2.6 million by 2010 and to 3.1 million by 2025.