Plastic pollution is now in the fossil record, according to new research from the Scripps Institution of Oceanography at the University of California San Diego. For the study, which was published September 4, 2019, in the journal Scientific Advances, scientists studied layers of earth in California’s Santa Barbara Basin dating back to 1834. They found that deposits of plastic have increased exponentially since the end of World War II, doubling around every 15 years.

Most of the plastic particles were fibers from synthetic fabrics used in clothes, said the researchers, suggesting that plastics are flowing into the ocean via waste water.

The increase of plastics in the sediments matches a rise in the rate of plastic production worldwide and a surge in California’s coastal population during the same time period. Jennifer Brandon of Scripps is the study’s lead author. She said in a statement:

This study shows that our plastic production is being almost perfectly copied in our sedimentary record. Our love of plastic is actually being left behind in our fossil record.

Brandon also told The Guardian:

It is a very clear signature. Plastic was invented and pretty much immediately we can see it appear in the sedimentary record.

The researchers analyzed annual sediment layers, collected from a core sample, that they dated back to 1834, looking for microplastics – tiny bits of plastic than 5 millimeters long (or about the size of a sesame seed) in the core sample layers. Most plastics were invented in the 1920s, but not used in significant commercial quantities until after World War II. The researchers found plastic in sediment dated to 1945, with the amount later increasing rapidly, so that by 2010 (when the samples were collected), people were depositing 10 times as much plastic into the basin as they were before World War II. The researchers said that the postwar period also showed a greater diversity of plastics, including fragments of plastic bag materials and plastic particles in addition to fibers.

Brandon suggested that the study results support the idea of using plastic accumulation as a defining signifier of the Anthropocene, a proposed new geological epoch marked by humanity’s influence on Earth. Specifically, Brandon said, the rise of plastics beginning in 1945, when the world recovered from war, could serve as a proxy for a time period within the Anthropocene that scientists have labeled the Great Acceleration, a period when humanity’s impact on our planet is increasing significantly. Brandon told The Guardian:

We all learn in school about the Stone Age, the Bronze Age and Iron Age. Is this going to be known as the plastic age? It is a scary thing that this is what our generations will be remembered for.

Bottom line: New research suggests that plastics have entered Earth’s fossil record.

Source: Multidecadal increase in plastic particles in coastal ocean sediments

Via Scripps Institution of Oceanography