Geologists sometimes label periods in Earth’s ancient history for the layers of minerals that formed at the time.
Our era? A new study argues that future geologists will label it the “Age of Plastic,” because since the 1950s the human-made material has become one of the most widely and abundantly deposited substances on Earth.
“A lot of geological time is fairly dull, despite the occasional volcanic eruption—whereas this is quite a change,” said study coauthor Jan Zalasiewicz, a geologist at the University of Leicester.
Plastic is “a signal of any kind of sediment deposited in the last half century or so, a marker of the Anthropocene, this great change in almost everything that’s taken place since the Second World War,” he said.
The researchers found that enough plastic has been manufactured since the mid-20th century to cover the Earth in a single layer of plastic wrap, and that barring a big change in current trends, by 2050 there will about 40 billion tons of plastic on Earth—enough to wrap the planet six times over.
The study was published in the journalAnthropocene; scientists increasingly use the term to refer to the present time because humans have become the dominant force shaping the planet’s environment.
Plastic objects decompose to some extent, leaving behind fossil-like traces that geologists have termed “techno fossils.” “So if one simply takes plastic and buries it, away from sunlight and erosion, it will leave a mark in the rocks of the future,” Zalasiewicz said. “I have no doubt that we will leave a layer that, looked at by anybody from the far future, shows fossilized plastic bottles and all the other things we make from plastic.”
More than 330 million tons of plastic are produced a year, or about 88 pounds for each of the world’s 7 billion people—roughly the weight of the global population. The qualities of plastic that make it so useful—its light weight, durability, flexibility, and resistance to decay—also contribute to its ubiquity in the environment.
The study found that less than 5 percent of plastic produced in the United States is recycled, while in Europe the amount is likely under 20 percent.
“One of the things that came as a surprise to me was when people have looked at Arctic ice, they found microplastics, particularly fibers of rayon,” said Zalasiewicz, noting that a single cigarette butt contains about 10,000 rayon fibers. (Cigarette butts are among the most frequently found plastic trash on beaches.)
The study estimated that at the current pace of polar sea ice melt, more than 1 trillion bits of microplastic could enter the marine environment in the next 10 years from the Arctic alone.
“When the ice melts, that plastic will travel and eventually wind up on some beach or the bottom of the sea,” he said. “A lot of it will pass through plankton and fish and seabirds—it will biologically cycle as well as being caught up in the sedimentary cycle, on a global scale.”
A growing body of research has documented widespread harm to wildlife caused by marine plastic pollution—and also suggests that the material is working its way up the food chain. A 2015 study estimated that tens of thousands of animals, including endangered marine mammals, seabirds, and sea turtles, had encountered marine plastic. Another found that one in four fish consumed by humans likely contains plastic debris.