Author of the best-seller, The World Without Us (2007), Alan Weisman is professor of journalism and Latin American studies at the University of Arizona. His other books include An Echo in My Blood (1999) and Gaviotas: A Village to Reinvent the World (1998).

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Journalist Weisman traveled the world to investigate what happens when humans stop occupying an area. How long do our artifacts last? How does nature recover? What does that say about the human impact on the world? What would be the actual sequence of events if all of humanity suddenly disappeared?

The exercise provides inspiration and techniques for humans to occupy Earth more lightly and therefore more durably.

Humanity's impact, nature's resilience

Weisman's book, The World Without Us, grew out of two questions, he said. One was, "How can I write a best-seller about the environment?" The answer to that was the second question: "How would the rest of nature behave without the constant pressure we put on it?"

On the border of Ukraine and Belarus is a small intact remnant---500,000 acres---of the primordial forest that once covered Europe from Siberia to Ireland. In the Puszcza Bialowieska, with its towering ash and linden trees and dense growth, Weisman felt he was in the forest of Grimm's tales. "It felt primally familiar. It felt like being home. I realized that people really want that back."

Buildings and cities without us around don't last long, his research showed. Water gets into every building, followed by rot, birds, and trees, and pretty soon all that's left is the bathroom tiles. The same with cities. New York is built on top of 40 streams. To keep the subways functioning, 13 million gallons of water have to be pumped out every day. If the water returns, it won't be long before the tall buildings lose their footing and topple.

Maintenance people emerged as the heroes of the book, Weisman said. Without their vigilance and toil, everything collapses. They are the bedrock of civilization.

At the New York Botanical Garden Weisman found that the 40-acre preserve of carefully protected original forest has transformed itself over the years into a new woods dominated by alien plants such as ailanthus and cork trees. The garden's curator told him something radical: "Maintaining biodiversity is less important than maintaining a functioning ecosystem. What matters is that soil is protected, that water gets cleaned, that trees filter the air, that a canopy generates new seedlings to keep nutrients from draining away into the Bronx River."

Plastic, Weisman discovered, is astonishingly durable, gradually accumulating in continent-sized gyres of floating garbage in the oceans. Instead of dissolving, the plastic just gets smaller in size and is ingested harmfully by every scale of animal all the way down to zooplankton.

Weisman's message is one of reconciliation. Wherever humanity backs its impact off even a little, nature comes swarming back. From the new part-wolf coyotes taking up residence in New England to the rare and exquisite red-crowned cranes prospering in Korea's Demilitarized Zone, accommodating nature always rewards humans.