How plastics are changing the planet

Future archaeologists aren’t just going to be digging up old bones: Looks like they’re also going to be sifting though old fossilized plastics.

A review published (paywall) in the journal Anthropocene this month finds plastic has discernibly changed the surface of the planet since humans began using the material in the mid-20th century. They see this as evidence that the Earth is entering what the study’s authors call the “Age of Plastics.”

This chart from the World Economic Forum report The New Plastics Economy Rethinking the future of plastics shows the growth in Global Plastics Production 1950–2014. Data source: PlasticsEurope, Plastics – the Facts 2013 (2013); PlasticsEurope, Plastics – the Facts 2015 (2015).

“If all the plastic made in the last few decades was clingfilm, there would be enough to put a layer around the whole Earth,” Jan Zalasiewicz, a paleobiologist at the University of Leicester and lead author of the study, said in a press release. “With current trends of production, there will be the equivalent of several more such layers by mid-century.”

For years, scientists have questioned whether or not we’ve entered a new geological timeframe directly impacted by human activity. In 2000, the Nobel-prize winning atmospheric chemist Paul Crutzen coined the term “Anthropocene” to mark the time when humans began putting an abundance of greenhouse gases, which contribute to global warming, into the atmosphere during the Industrial Revolution. The term is frequently cited by the media and researchers, but it is not yet officially recognized on the geologic time scale due to ongoing debate over its merit. Zalasiewicz and his team conducted their research on the long-term environmental effects of plastics as part of the search for more concrete evidence of the proposed epoch.

The researchers looked at existing literature and determined that the geological cycle—or lifetime—of plastics suggests they may be a “key geological indicator of the Anthropocene, as a distinctive stratal component.”

Plastics break down slowly if they’re not recycled. On land, untouched plastics can become integrated into the soil beneath our feet. In landfilles, the authors write that “plastics may be expected to survive even longer,” because landfills are often closed-off facilities designed to dehydrate waste. Discarded plastics that make their way into the ocean can remain intact for so long they can form garbage patches—if they’re not eaten by an unsuspecting sea creature first. Eventually, ocean plastics will also reach the bottom of the ocean.

Over time, these plastics become covered with other kinds of sediment, like dirt and rocks. Zalasiewicz suggests that, like bones or plants we see in museums today, these plastics “have a good chance” to become fossilized. The reviewers dubbed these future, preserved materials “technofossils.”

“It may seem odd to think of plastics as archaeological and geological materials because they are so new, but we increasingly find them as inclusions in recent strata,” says Matt Edgeworth, an archaeologist at the University of Leicester and co-author of the study. They’re “excellent stratigraphic markers,” he said.

And with the amount of sturdy, throw-away plastic products we’re churning out now, Zalasiewicz hypothesizes that “the age of plastic may really last for ages.”