In The World Without Us, Alan Weisman goes off the beaten track to speculate on the future of planet Earth. What he presents is not so much an inconvenient truth as an unconventional thought: what would happen if humanity suddenly disappeared? He spends little time conjecturing how this might happen, apart from noting that its unlikelihood doesn't make it impossible. But what might have provoked a ho-hum response is rescued by Weisman's devotion to his task.

From the demilitarised zone between the Koreas, to the green line separating Greek and Turkish Cyprus, from the underground caves of Cappadocia to Chernobyl's fallout zone, Weisman sets out to bear witness to a world without humans. Along the way, he consults an impressive array of experts happy to play along with his preposterous proposal.

Before embarking on his journey to the future, Weisman begins in the past. Bialowieza Puszca, on the Polish-Belarus border, is teeming with wildlife and groaning with 500-year-old oak trees. The relic of a primeval forest that once stretched from the Atlantic to Siberia, this unsung patch of land truly is the way we were. And, according to Weisman, it may well be the once and future planet. For if humanity were suddenly to disappear, much of the world would revert to this ancient landscape.

Most city-dwellers imagine that man has conquered nature. But within minutes of us moving out, the elements, the weeds and the wildlife would move in. Using the ultimate city as a model, Weisman describes how the New York subway would flood within 36 hours of humanity's demise. After a couple of decades, the great forest of Manhattan skyscrapers would have toppled over, their foundations undermined by a rising tide of water. The concrete jungle would be replaced by a real one, trees and plants no longer uprooted by urban busy bodies. Those parts of the city not over-run by greenery would be submerged by water. If they managed to withstand all of this, along with earthquakes and lightning strikes, the Big Apple's mighty bridges could last as long as a millennium. Protected by her bronze cladding, the Statue of Liberty would also remain intact, albeit in a watery grave.

Beyond the cities, Weisman's span covers the countryside, the seas, the atmosphere flora and fauna. But, with each passing chapter, an unmistakeable message emerges: long after every trace of human life has vanished, our terrible legacy will live on.

Even if the animal and plant kingdoms were to survive UV radiation from an expanding hole in the ozone layer, or a massive poisoning of the atmosphere from exploding petrochemical plants, they would still have to contend with the deadliest of man-made dangers. The contamination of air and water from hundreds of overheating nuclear power stations would unleash a nuclear winter spanning geologic time. Soil creatures would find no respite: heavy metals ploughed into the land by herbicides and pesticides would take thousands of years to degrade. Fish stocks may recover once man is no longer around to plunder the seas. But the millions of tonnes of plastic littering the world's oceans will continue to kill creatures great and small, whether or not we are there to witness it.