A.H. (After Human)

In some crystal balls, we're not around

In his 2007 book The World Without Us, American journalist Alan Weisman ponders the state of the planet after the last humans have gone, from deteriorating buildings and overgrown cities to the lasting quality of such man-made things as Mount Rushmore and radioactive waste.

Time ranked the book #1 on its top 10 non-fiction list for that year.

In January 2008, the History Channel offered its own view, with the documentary Life After People, which detailed a span of 10,000 years beginning with the sudden disappearance of the entire human race.

Months or even years after we're gone, the show's writers hypothesize that the lights of Las Vegas would be the only surface light seen from space, as the city would continue to be powered by the Hoover Dam, which can automatically supply electricity as long as Lake Mead had water.

With 5.4 million viewers, Life After People was the History Channel's most-watched program.

In March 2008, the National Geographic Channel joined the growing chorus of soothsayers with Aftermath: Population Zero, which started with Day 1 A.H. (a new time designation for "After Humans") all the way to 25,000 years A.H, when the last vestiges of New York City disappeared under the weight of a new ice age.

Now, New Scientist reporter Bob Holmes offers his own apocalyptic future view in "Post-human Earth: How the planet will recover from us."

"In two or three hundred years," Holmes imagines an "ecological collapse and a mass extinction" from man's "orgy of global warming and overconsumption."

Holmes interviewed several scientists, including paleontologist Tony Barnosky from the University of California at Berkeley, who says that after fossil fuels have run out, effectively bringing agriculture to a halt, "a lot of things have to die, and a lot of those things are going to be people."

"If we were to blow all the fossil fuels into the atmosphere, temperatures would go up to the point where both of these reservoirs of carbon would be released," says geophysicist David Archer from the University of Chicago.

For a clue as to what might happen, many scientists have been looking to the Paleocene-Eocene Thermal Maximum (PETM), a period about 55 million years ago when the Earth's temperature rose rapidly concurrent with a spike in atmospheric carbon dioxide, a situation that caused numerous extinctions.

But James Hansen, director of NASA's Goddard Institute for Space Studies says that those kinds of geo-historical studies won't tell us too much, as the Sun is much brighter now that it was back then.

Climate predictions are tough to make. What we do for certain is that the planet can withstand dramatic changes in its atmosphere. For the living things that call Earth home, it's an entirely different story.

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image: Reynard Loki