Friday, October 13, 2006

Without a trace - eventually

(Click on graphic to enlarge)
Suppose Nature declared her experiment with the human species a failure and decided homo sapiens should go the way of extinction (or face a less painful fate as the folks at New Scientist suggest and were teleported to some distant galaxy). What would be the impact if all of our footprints were removed from the face of the Earth? Read on. (GW)

200,000 years for all trace of Man to vanish from the Earth
by Lewis Smith
The Times of London
October 12, 2006

IF MAN were to vanish from the face of the Earth today, his footprint on the planet would linger for the mere blink of an eye in geological terms.

Within hours, nature would begin to eradicate its impact. In 50,000 years all that would remain would be archaeological traces. Only radioactive materials and a few man-made chemical contaminants would last longer — an invisible legacy.

Homo sapiens has managed just 150,000 years on Earth, and his earliest — debatable — ancestor only six million. By contrast, the dinosaurs populated the planet for 165 million years.

Man’s environmental footprint would, according to a report in New Scientist, begin to deteriorate almost immediately, with light pollution the first to go as power stations ceased to provide energy.

By tomorrow, street lights and house lights left on by their former occupants would start to go out.

Streets and cultivated fields would be the next to go. Within 20 years village streets and rural roads would have vanished under a matting of weeds; fields would be overgrown within months. Urban streets would take a little longer, but even in huge man-made sprawls, such as London and Birmingham, plants would have taken over in about 50 years.

Buildings would decay rapidly. Wooden structures would collapse first, assaulted by bugs and grubs. All such homes would be gone in a century.

Glass and steel tower blocks that create city skylines would mostly fall down within 200 years. Brick, stone and concrete structures would last longer. With exceptions — the pyramids are already 3,000 years old — by the next millennium there would be little more left than ruins.

“If tomorrow dawns without humans, even from orbit the change will be evident almost immediately,” Bob Holmes, of New Scientist, said. “With no-one to make repairs, every storm, flood and frosty night gnaws away at abandoned buildings and within a few decades roofs will begin to fall in and buildings collapse.”

Ronald Chesser, of Texas Tech University, said: “The most pervasive thing you see are plants whose root systems get into the concrete and behind the bricks and into door frames and so forth and are rapidly breaking up the structure.”

Wildlife would thrive in the absence of Man. Most of the 15,589 threatened species will begin to recover immediately towards historical populations.

Carbon dioxide emissions wouldcontinue to cause climate change for another 100 years, but after 1,000 years all would be back to pre-industrial levels, with all man-made traces vanishing in 20,000 years.

However, the most radioactive of untreated nuclear waste would not be safe for up to two million years, John Large, an independent nuclear consultant, said. Man-made chemicals, especially perfluorinated types, would not break down for up to 200,000 years, although it is thought that they would have been buried long before then.

If, 50,000 years hence, an alien archaeologist were to land on an Earth without Man, it might be quite frustrated by the paucity of evidence that we were here at all.

Click here to read the New Scientist article "Imagine the Earth Without People".


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