What if we no longer existed?

If humans were to disappear suddenly from Earth, Minnesota's harsh climate would quickly start undoing decades of development in the Twin Cities.

Early spring's freeze-thaw cycle would break up concrete and asphalt as water from melted snow filled cracks in the streets and sidewalks during the day and then refroze at night, says Alan Weisman, author of "The World Without Us."

Silt and debris would build up along dams and banks of the Mississippi River and other waterways, and the resulting floods would help restore the wetlands that once existed.

"All of the wood frame houses that I grew up in, on the North Side of Minneapolis and in St. Louis Park, in a century would be lying on the ground," Weisman said. Even though humans would be gone, he added in jest, "The Vikings would go on losing."

Weisman, 60, now lives in western Massachusetts and teaches occasionally at the University of Arizona, but he will return to the Twin Cities next week to discuss "The World Without Us" at the University of Minnesota and elsewhere. He chatted about his hot bestseller last week by phone while driving through Arizona's desert canyons.

Q After reading your book, one has to wonder, is the world better off without us?

A Well, I did not write this book because I think that we are a scourge on the planet and that it should get rid of us, because I think we deserve to be here as much as any creature that has evolved this far. But I think that we belong here in a harmonious, balanced relationship with nature, not in mortal combat with nature -- and that's where we are right now.

Q What has been the most damaging aspect of human presence?

A There are three things that immediately leap to mind:

One, the way we use energy. We require so much concentrated energy that we dug deep into the Earth to find locked-up energy that nature didn't really need to do its thing. And it's worked great -- I'm driving a car now while talking to you, and we're talking through electric devices. But the unfortunate consequence is waste material, carbon dioxide, going up in the atmosphere and causing this big problem that seems to be affecting our climate.

Two, food production. A third of the terrestrial Earth that we inhabit is devoted to grazing or cultivation. We've mowed down so much wilderness to grow our crops. And we've grown mechanized, monocultural crops that require large amounts of chemicals, such as fertilizers and pesticides.

Three, overpopulation. The explosion of agriculture has resulted in human population rising to meet the food supply, while medical technology has lowered mortality rates.

Q Humans have caused the disappearance of many plants and animals. If you could bring one thing back, what would it be?

A I'm a bird lover. I grew up in Minneapolis on a wetland that has now been paved over. When I was a kid, I had an Audubon bird guide. It was the first book I ever bought -- got it at Dayton's, and I still own it. I used to go to the Minneapolis Public Library, and they had a stuffed passenger pigeon in a glass case. It explained that these things were wiped out by 1914, that this used to be the most numerous bird on Earth and that humans learned a terrible lesson from this. I would love for the passenger pigeon to come back, and I would love for it to do so with a vengeance so we could get a chance to learn that lesson again.

Q Do you see something like the collapse of the I-35W bridge as evidence for some of the scenarios you present in the book?

A I was supposed to be interviewed on Minnesota Public Radio that day, but we postponed. My condolences to everybody, because I've been over that bridge a zillion times and so many people I love have. It's a tragedy that it happened.

But everywhere in the book, there are people who are keeping subways pumped, or maintaining bridges or showing up at our nuclear plants. These are the real unsung heroes. If politicians and policymakers disappeared, I think society would survive. But you get rid of the maintenance people, and it would all crumble. They are the worker bees upon whom our lives depend.

Q Is there any positive news for humans?

A We do make a beautiful contribution to this planet, just like any other species, and in original ways. Our great stone buildings, some of them from biblical times, will last a long time. It's a beautiful thing to think that some of that stuff is so resilient. And even though we have introduced a lot of non-native species for agricultural purposes, it's pretty to think, for example, that there may be growths of apple trees in places around the Earth that will indicate that we were here.

But the fact is that we are growing our population by a million people every four days. We are going to suffer a population crash someday, because every species that outstrips its resource base in their biological history does crash.

There is a way that it doesn't have to be catastrophic, and that is if we as a species decide to do something that sounds difficult: limit our population.

What if there were fewer of us? What if we only all had one child, instead of multiple children? I'm not advocating this wholeheartedly, because, heck, I'm a second child in my family. But we're going to have to do something. If we don't manage it in a humane way through attrition, nature's going to hand out a bunch of pink slips, and it's going to be brutal.

Randy A. Salas • 612-673-4542