Humans’ impact on the earth has pushed the world into a new geological period which will be characterised by fossils of plastic, concrete and nuclear energy, scientists say.
Like the dinosaurs of the Jurassic age, scientists say humans have also had an impact on the fossil record. In 2016, the International Commission on Stratigraphy will meet to consider whether humans made such an impact and today, in the journal Science, a group of eminent scholars argue this new epoch should be recognised by the commission.
They argue this period, like the “age of the fishes” or the “age of the dinosaurs” before it, should be defined by the dominant species on the planet: humans.
One of the authors of the article, Australian National University’s Professor Will Steffan, said: “When stratigraphers look at what is forming in the sedimentary record — what will be the rocks of tomorrow — they see all sorts of things that are decidedly different and occurring around the globe at around the same time.”
“From their criteria, they can see a change occurring and this would be a new geological time period.”
Here are 10 ways the scientists say humans will leave behind fossils.
1. Rubbish tips
Much in the same way as later arrivals to Australia have mapped early Aboriginal movements by discovering their middens, fossil-hunters of the future will know us by our garbage.
But unlike first Australians, the signature of later generations will be more than piles of shells and bones. Humans have invented all manner of materials to help us with our daily lives. Some of which are very long-lived.
Pottery, glass, bricks, and copper alloys will all be around years after we have gone. Even the humble soft-drink can is a geological marvel. Some 98 per cent of all the aluminium ever produced has been dragged from the Earth and refined into useful products since 1950.
It was the Romans who invented concrete, but it has really taken off in the past 20 years. More than half of all concrete ever produced has been made since 1995. It is enough to cover every metre of the planet’s surface with a kilogram of concrete.
Plastic — an entirely human invention — has entered waterways and oceans and spread to every part of the globe. Because it does not readily break down, it is expected it will signal the presence of humans long after our species fades away.
“Plastic has been a ubiquitous material since 1950 and has increased enormously. In fact, if you take the plastic film that we use in our kitchens, every year we use enough to completely cover planet Earth,” Professor Steffan said.
All around the world, minerals are being dug up in one location, refined and transported to a new location. Along the way, huge pits and tunnels are bored into the Earth and a massive volume of soil is shifted. Three times more soil is shifted by miners each year than by all the world’s rivers. We’re like earthworms but on a much grander scale, Professor Steffan said.
“We’ll leave record of holes, tunnels and pits that will be around for millions of years.”
Since we started farming, about 10,000 years ago, humans have been clearing forests to make way for crops. But it is the way we use fertilisers that the scientists think will still be evident in millions of years.
“The amount of nitrogen that flows through the Earth’s system has been more than doubled by the fact that we take nitrogen out of the atmosphere and fix it into reactive forms that help us grow crops,” Professor Steffan said. “But we use far more than what we need to grow the crops. This ends up in rivers, in drinking water and in coastal zones, and causes massive algal blooms.”
Maybe some of us will be unlucky enough to be caught in a swamp and turned into a fossil, but regardless, human bones and the bones of our livestock will become boringly common for fossil hunters in the future.
Professor Steffan said: “If you look at the mass of wild animals — mammals — that are out there, it’s only 5 per cent of the total mass of mammals.”
“The other 95 per cent are us and our domesticated animals — cows, pigs and sheep and so on — so the fossil record is going to be enormously dominated by humans and our domesticates in the future.”
Around the world, everything is being coated with a thin layer of grime from pollution in our skies. This layer is expected to signal to future fossil hunters our love of fossil fuels.
“Soot filters out of the atmosphere pretty quickly because it’s particles and it’s heavy,” Professor Steffan said. “But it’s leaving a sedimentary record around the world that is undeniably related to the massive burning of fossil fuels, particularly since the mid-20th Century.”
8. Climate change
You’ve heard of carbon dating, where scientists determine how long fossils have been in the ground? Well human-caused climate change may ruin carbon dating for future scientists.
The way carbon dating works is by comparing the ratio of one kind of carbon atom with another. The two kinds are known as isotopes. But climate change could throw the ratio out of whack.
“Fossil fuels have a different ratio of carbon isotopes from living carbon — that is, from burning trees,” Professor Steffan said. “And that will leave a long-term record in the sediment of the fact that we have put a massive amount of fossil carbon buried for millions of years suddenly into the atmosphere.”
9. Sea level rise
Not only is climate change mucking up the delicate balance of carbon isotopes in the atmosphere, it’s causing sea level rise on a scale not seen since the beginning of the current geological epoch, known as the Holocene.
10. Nuclear bombs
The first nuclear bomb was tested on July 16, 1945. The scientists propose this as the official start of the new geological era as from here, varieties of atoms never before seen in nature came into being and they will continue long after the last human dies.
“They are unknown in nature. They are absolutely and unequivocally due to human activity,” Professor Steffan said. “They’re long-lived isotopes and because they spread around the atmosphere and settle out and will be in the sedimentary record for millions of years.”
The scientists propose adopting the term Anthropocene to describe the new geological era. The term, which means “age of humans” was first proposed by chemist Paul Crutzen in 2000 to the International Commission on Stratigraphy, and support has been building since.
Professor Steffan believes a ruling from the commission might spur the human species into thinking more carefully about our impact on the planet.
“I think the thing that the Anthropocene might do is act as a wake up call to say, ‘All right we are very powerful’,” he said.
“There’s no doubt about that we’re clever, we’re technologically amazing. But are we wise? Because we’re the first generation to have the knowledge that we’re impacting on the entire Earth system.”
Read the article on The ABC.