Introduction to the Anthropocene Era

Plastic may have marked the beginning of a new geological era on our planet, often referred to as the Anthropocene. In the future, hundreds or even thousands of years from now, scientists may use sediment layers containing bits of old plastic to date them, similar to how archaeologists today date excavations based on the art styles of ancient pottery. This method has already been employed: researchers have revealed the history of bird nests in The Netherlands by examining the plastic litter used in their construction.

The Impact of Plastic on Bird Nests

Many bird species, including the common coot, have started incorporating human-made food and drink packaging into their nests. This behavior allowed three biologists to reconstruct the individual histories of dozens of common coot nests in Amsterdam by simply reading the expiration dates on the plastic. However, there’s a significant issue: these nests aren’t supposed to have a history because common coots don’t typically reuse their nests from year to year. As outlined in a study published in the journal The Scientific Naturalist, plastic has not only turned bird nests into time capsules but may also be fundamentally impacting the evolution of certain species.

Uncovering the History of Bird Nests

Image: Overview of packaging dates. Photo by Auke Florian Hiemstra

Auke-Florian Hiemstra from Leiden University collected over a dozen empty coot nests to investigate this new nesting behavior. By deconstructing and sorting the nests into two piles – one with natural materials and one with human-made materials – Hiemstra was able to date layers of the structures accurately using the expiration or packaging dates on the human-made materials.

A History Book of Plastic

“You flip through these nests like through pages of a history book, uncovering the past,” Hiemstra said in a statement. One of the most striking nests contained 635 artificial items, 32 of which were food-related waste with dates going back decades. Almost half of these datable materials were from McDonald’s, and they even found a Mars wrapper advertising the 1994 FIFA World Cup in the United States.

The Timeline of Plastic in Bird Nests

Image: Plastic in bird nest timeline. © Auke-Florian Hiemstra

The researchers explained, “From these dateable items, a picture emerges of what happened at this nesting site over the past 30 years. As the nest was located at a dock for tour boats, which were constantly mooring, the nest could not be deconstructed layer by layer in chronological order. Yet, while collecting, we observed recent top layers of face masks and the deepest layers of nest material showed plastic dating back to the early 1990s.”

Confirmation Through Google Street View

Cross-referencing these dates with archived Google Street View imaging confirmed that “Coots were indeed nesting in the years corresponding to the expiration dates found in the nest.” In total, Hiemstra and his colleagues identified 15 common coot nests whose use of plastic materials pointed to a multi-year existence.

Evolutionary Advantages

The researchers suggest that this new behavior may give the birds evolutionary advantages. For example, coots that simply add more material to previously existing nests have more time and energy to defend their territory and breed than coots that have to build from scratch.

Conclusion

“Layer upon layer, with every new breeding attempt, an accumulation of plastic litter in stratigraphic order is laid down, which forms a historical time series,” the researchers concluded. “The serial deposits, constructed out of artificial material, may not only document the history of a bird nest but also reflect the history of our Anthropocene Epoch.” It’s difficult to say how future researchers will interpret our layers of waste, but one thing is clear: humans are leaving a lasting impact on Earth, evident in plastic found in everything from birds’ nests to Iron Age archaeological sites.