When Christopher F. D'Elia was growing up 40-some years ago in the Washington, D.C., area, the nation's capital was like "a small Southern town," he recalls.
Where he lived, in Arlington, Va., was at the limits of urban development. "It was country beyond there," he says. The world itself seemed much smaller then, too.
How things have changed.
Washington is now a sprawling megalopolis, with suburban tentacles reaching deep into the former farmland and forests of Maryland and Virginia. The number of people living in the region, which drains into the Chesapeake Bay, has grown more than 50 percent in the past four decades.
Those changes are "awesome" and profoundly troubling to Dr. D'Elia, who is now an ecologist and professor at the University of Maryland's Chesapeake Biological Laboratory in Solomons.
The future of the Chesapeake, and of the Earth itself, hinges on our ability to curb our burgeoning numbers, Dr. D'Elia said in a recent interview. While population in the bay region was growing 50 percent, world population was growing more than 100 percent. And unless we come to grips with population growth, he warned, all the Earth Day tree plantings and windy meetings like the upcoming "Earth Summit" in Brazil will not be enough to save the bay or the world from environmental catastrophe.
"We're really teeter-tottering on the brink of disaster," he said. But few leaders are willing to talk about the need for population control because the abortion debate in this country has made it a "political hot potato."
"Regardless of the means we want to use to reduce population, we've all got to be talking about it," Dr. D'Elia said.
On the bay, after spending hundreds of millions of dollars to dTC overhaul sewage plants in Maryland, Virginia and Pennsylvania, "we're holding our own against a tide of demographic change," said Dr. D'Elia, director of the Maryland Sea Grant College program.
But in the next 25 years or so, another 2.6 million people are expected to join the 13.6 million residents already living in the three-state bay watershed. Pollution from the cars and trucks they drive, from the power they consume and from the lawn fertilizers they use will add stresses to a fragile and already degraded estuary.
Globally, the picture is even grimmer, he said. The planet's populace is increasing by more than 90 million, or roughly the size of Mexico's current population, every year.
The United Nations predicts that the current world population of 5.4 billion is likely to increase to 10 billion by the year 2050, and to 11.2 billion by 2100.
Malnutrition is growing now in Africa, where soaring birth rates have collided with crop failures and drought. Population pressures also are leading to rapid deforestation and soil erosion, in a desperate search for arable land.
The United States and other industrialized countries are a big part of the global population problem, too, even though their birth rates are lower than those of the Third World. Americans consume far more resources and generate more waste and pollution than do residents of poor nations.
One example: emissions of carbon dioxide and the other pollutants that scientists believe may produce global warming in the next 50 years. The United States releases nearly nine times as much of those "greenhouse gases" per person than does China and more than 14 times as much as India.
Not everyone agrees that population growth is a problem. Conservatives say that government policies, not too many people, are to blame for the world's hunger, poverty and environmental degradation.
"If the world had market economies, much of the world's environmental problems would be solved," contends Fred L. Smith Jr., president of the Competitive Enterprise Institute, a Washington think tank.
Critics say world population growth has been slowing since the mid-1960s, and they say the "green revolution" of the 1970s -- with its emphasis on modern agricultural techniques -- boosted food production and eased starvation in developing countries, especially in Asia.
"In fact, we may be moving towards a better world, rather than a worse world," asserts Mr. Smith.
But many scientists disagree. The U.S. National Academy of Sciences and the Royal Society of London recently issued a joint statement that "science and technology alone are not enough" to cope with the projected global population explosion.
"Are we going to bet our quality of life on the hope that there's going to be some technological fix to every problem?" asked Dr. D'Elia. "I think the odds are against us."
The U.N. population projections already assume birth rates will drop significantly in the next 50 years; if they don't, world population could more than triple to 19 billion.