Next they looked at what had happened to animals and plants. Past shifts in geological time have often been accompanied by mass extinctions, as species struggle to adapt to new environments. In 2011, research by Anthony Barnosky, a member of the group, suggested something similar was underway once again. Others investigated the ways humans have scrambled the biosphere, removing species from their natural habitat and releasing them into new ones. As humans have multiplied, we have also made the natural world more homogenous. The world’s most common vertebrate, the broiler chicken, of which there are 23bn alive at any one time, was created by humans to be eaten by humans.
Then there was also the matter of all our stuff. Not only have humans modified the Earth’s surface by building mines, roads, towns and cities, we have created increasingly sophisticated materials and tools, from smartphones to ballpoint pens, fragments of which will become buried in sediment, forming part of the rocks of the future. One estimate puts the weight of everything humans have ever built and manufactured at 30tn tonnes. The working group argued that the remnants of our stuff, which they called “technofossils”, will survive in the rock record for millions of years, distinguishing our time from what came before.
Nicola Davison
Ah, the good old days of 2019, when scientists could afford these kinds of academic arguments – and I could find the time to read about them. There are certainly arguments for both sides of the debate: humans have done much to change ecosystems to better suit our needs (and plan to continue), and our discarded products may well survive for millennia. I personally lean towards the ‘against’ side, meaning any effects of human civilization will be quickly swept away by natural processes once we are gone.
But the simple truth is we cannot answer this dilemma unless we can estimate how long our industrial civilization will survive on Earth – and in which form. If it crumbles under the effects of climate change within the next century, its footprint in time will be small and easy to erase. But the longer human civilization lasts, the more pronounced its effects on the geological record should become. It would indeed be humanity’s greatest achievement if we manage to sustain a global thriving civilization over centuries and millennia without simultaneously wrecking the planetary environment.
The most enduring geological legacy, instead, will be the extinctions we cause. The first wave of human-driven extinctions, and the largest hit to terrestrial megafauna since the extinction of the dinosaurs, began tens of thousands of years ago, as people began to spread out into new continents and islands, wiping out everything we tend to think of as “Ice Age” fauna—mammoths, mastodons, giant wombats, giant ground sloths, giant armadillos, woolly rhinoceroses, giant beavers, etc. This early, staggered, human-driven extinction event is as reasonable a starting date as any for the Anthropocene and one that has, in fact, been proposed. However, a few thousand years—or even a few tens of thousands of years—will be virtually indistinguishable in the rocks a hundred million years hence. That is, it would not be obvious to the geologists of the far future that these prehistoric human-caused extinctions were not simultaneous with our own modern-day depredations on the environment. The clear-cutting of the rain forest to build roads and palm-oil plantations, the plowing of the seabed on a continental scale, the rapid changes to the ocean and atmosphere’s chemistry, and all the rest would appear simultaneous with the extinction of the woolly mammoth. To future geologists, the modern debate about whether the Anthropocene started 10 minutes ago or 10,000 years ago will be a bit like arguing with your spouse on your 50th wedding anniversary about which nanosecond you got married.
Peter Brannen
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