If everyone vanished from Earth overnight, how long would it take to obliterate all traces of mankind? Alan Weisman asks and answers that morbidly intriguing question in The World Without Us.

What philosophical or environmental tipping point led to your book's premise?

It wasn't any one thing. I've been covering environmental issues since 1991. Rainforest destruction, melting glaciers, unusual bird migrations—something was happening. And I couldn't forget what the scientists I spoke to were saying: if we wait until we can be 100% certain of a trend, it'll be too late. This book asks the question, is it?

According to your research, New York's subways will flood within days without us, but it might take microbes hundreds of thousands of years to devour plastic. Were you surprised by either time line?

It's no shock that it rains in Manhattan. Before the island was settled, streams carried away rainfall. Today, Manhattan is an enormous feat of civil engineering, with 800 pumps constantly at work. So when the power goes off, flooding is inevitable. Plastic bags came into use just 50 years ago, and now billions are clogging landfills and polluting oceans. I'm heartened that something will eventually come along to metabolize the stuff.

The Mayan culture, you write, self-destructed after centuries of maintaining a delicate ecological balance. Is that what we're doing to ourselves?

What happened to them is symbolic of what we're doing on a planetary scale. We're out of balance with our surroundings. There's an enormous environmental price to pay for having blueberries year-round, an enormous cost in defending energy resources halfway around the world—we see that now in Iraq.

Bridges rust, skyscrapers topple, but broadcast signals will rocket into the universe forever, representing a world long dead. What program do you want defining you?

I haven't watched TV since I was 11, after reading Robert Heinlein's description of the “boob tube.” But in 1972, a three-hour Minnesota radio show by a guy named Garrison Keillor—a mix of music and whimsy, before the Prairie Home Companion phenomenon—kept me warm on cold winter mornings. I'd like that show to represent me somewhere out there.

You say that “our world would start over” after we're gone. But in a coda, you suggest extreme restrictions on birth rates to ensure our continued presence. Was that your survival instinct kicking in?

The book's thesis is a kind of fun fantasy. It posits a world without us as a way of disarming readers' fear of a scary, depressing environmental future. But lurking within is the thought that if the world could flourish beautifully without us, wouldn't it be nice to stick around?