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 it. In 50,000 years, all that would remain would be some 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 its earliest - debatable - ancestor only six million.
By contrast, the dinosaurs populated the planet for 165million 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 thick 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 Sydney, plants would have taken over within 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 3000 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,” said Bob Holmes, of New Scientist.
“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 people. Most of the 15,589 threatened species would begin to recover immediately towards historical populations.
Carbon dioxide emissions would continue to cause climate change for 100 years, but after 1000 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, independent nuclear consultant John Large said.
Man-made chemicals, especially perfluorinated types, would not break down for up to 200,000 years, although it is thought they would be buried long before then.
If, 50,000 years hence, an alien archaeologist were to land on an Earth without man, it might find quite frustrating the paucity of evidence that we were here at all.
The Times