A new documentary on what the earth would look like if humans ceased to exist, shows evidence of even the greatest cities would all but disappear within 1,000 years
It's a fate that would befall structures like the Sydney Harbour Bridge much sooner. It'd probably collapse within 100 years.
Life After People, the most watched documentary to air on The History Channel when it premiered earlier this year in the US, will air on pay TV in Australia next week.
The documentary has used engineers, biologists, and a range of experts to create images of what the world will be like if mankind dies out.
It takes viewers from day one, right up to 10,000 years after extinction and shows that within 1,000 there would be little signs left of contemporary life.
But there will be rare exceptions. The Hoover Dam in the US is expected to be still standing up to 10,000 years later.
British civil engineer Gordon Masterton who worked on the program said his research showed that it would be a very quick process for everything to start breaking down.
The process would begin within hours.
"There's going to be evidence (of modern life) left after a hundred years or so, it won't be habitable, but it will still be there," Masterton told AAP.
"But in 1,000 years there'll be very little sign of modern buildings left behind."
The documentary shows that within hours of a world with no people, lights all across the globe would start going out as electrical systems began to fall apart.
By a week or so, the New York and London subways would be flooded.
Within a year, all radio and television signals travelling through space would end and wild fires would rage.
By five years, plant life like vines and grasses would cover cities.
By 25 years London and Amsterdam would be flooded and high rise buildings would begin to crack.
Large structures like the Golden Gate Bridge and Brooklyn Bridge would start to collapse after 100 years because of corrosion.
It's not in the documentary but Masterton said the Sydney Harbour Bridge would be among structures to fall down after 100 years.
It would take another 100 years before the Empire State Building and Eiffel Tower start to fall down.
While modern cities wouldn't be around in 1,000 years, structures like the Egyptian Pyramids or the Great Wall Of China were expected to have more chance of surviving.
The documentary says the Pyramids, portions of the Great Wall of China and the faces on Mount
Rushmore could still be around hundreds of thousands of years later.
Aside from very domesticated pets, animals would be fine without humans and life in the ocean would quickly get back to levels before human consumption.
Masterton said that he hoped the documentary helped people realise how much maintenance was required to keep modern society going.
"There's a lesson there with how quickly it would take for whole cities to be indistinguishable from what they are, and the contribution the engineering infrastructure make behind the scenes is really significant," he said.
"Every time you turn a tap on or flick an electricity switch the reason why we get water and electricity is behind that, there's a huge army of engineers and technicians maintaining what we've got."
The documentary has been made amid a growing fascination about what the world will be like without people.
It doesn't try to speculate how people will die out.
Two similar documentaries have aired in the US, and a recent book, Alan Weisman's The World Without Us, is on the best seller list in a number of countries.
The two-hour documentary will air on Foxtel and Austar on The History Channel on Monday, May 19.