Lester Brown, global watchdog, can cite enough looming catastrophes to spoil anyone's day: Water tables are falling; temperatures are rising; rain forests are shrinking.
Gordon Hempton, professional "sound tracker," faces a simpler problem: It's getting awfully hard these days to find 15 minutes of peace and quiet.Each man, in his own way, is talking about the same thing. A lot more people live on the planet than ever before, and by and large we're a hungry, needy, noisy bunch. Of all the changes the 20th century has seen, none is more far-reaching than the explosion of human population -- the one trend to which everybody contributes.
One hundred years ago, 1.6 billion people lived on Earth. This year, world population will reach 6 billion.
How to keep all those people alive without ravaging the planet is a question Brown addresses daily as president of the Worldwatch Institute, an environmental research group based in Washington, D.C. Yet even he remains awed by humanity's talent for multiplication.
"There has been more population growth since 1950 than during the preceding 4 million years," Brown says.
While Brown's path to comprehension is paved with Big Picture charts and graphs, Gordon Hempton has a more personal way of measuring how crowded the world has become.
From his home in Port Angeles, Wash., Hempton treks to remote corners of the world with an expensive tape recorder in hand, seeking to capture nature's quiet symphony.
Trouble is, few places remain where human noise doesn't intrude. In rural glades of the southeastern United States, Hempton has tried in vain to escape the low drone of "monster flutes" -- the smokestacks of coal-fired electric plants dotting the landscape. In Wyoming, his quest for quiet has been interrupted by the rhythmic booming of oil-well pumps. Even in the Southwest's lonely deserts, he finds no peace.
"If you listen in the middle of the night, the desert landscape is actually rumbling," he says. "A tremendous amount of sound is being pumped out from distant cities, highways, power transmission lines, industry and mining."
Fifteen years ago, Hempton documented 21 spots in Washington state where he could reliably capture 15 minutes of natural sounds uninterrupted by the likes of roaring jets, humming trucks and barking dogs. Now he finds only three.
He mourns the loss. When we can't escape noise, our senses start shutting down and life is not as sweet, Hempton believes.
And so, in his own quiet way, he reaches the crux of the population question: It's not whether 6 billion or 16 billion people can be crammed onto the planet. It's the quality of life those people enjoy, whatever their number.
Hempton craves solitude. Others want gasoline for their cars and electricity for their computers. Millions would settle for a daily loaf of bread or bowl of rice. Can the globe support us all in the manner to which we are accustomed?
Some don't consider the century's near-quadrupling of population a problem.
"We should celebrate it," says Jerry Taylor, director of natural resource studies for the Cato Institute, a conservative think tank in Washington. "It's a product of improving human health, improving lifestyles and better nutrition. People are living longer."
While others worry that too large a population will exhaust natural resources, Taylor says human ingenuity is the true resource -- and that will only increase with more people around.