Graphic by Annabel Driussi for ODP

by Amy Lupica, ODP Staff Writer

Invasive species are hitching a ride on increasing ocean plastic pollution, surfing to distant shores. For centuries, stowaways like zebra mussels arrived on the hulls of ships, but now, hundreds of species are “rafting” across oceans on marine litter. These invasive species now threaten the balance of ecosystems across the globe and exacerbate biodiversity loss.

Experts say that the only way to prevent this mass migration is to remove these “rafts” and halt ocean plastic pollution in its tracks.

Why This Matters: It’s well known that plastic pollution can harm wildlife, especially sea birds and marine species. But plastic rafting poses a threat that hasn’t been studied in-depth, and as garbage patches and plastic litter increase worldwide, this migration could become exponential.

Non-native species can overtake the habitats of native species, put a strain on resources, and even carry disease. Experts say that, while rafting has been sporadic throughout history and has been used to explain the distribution of many species, including humans, it’s quickly becoming a constant occurrence. Now, plastic isn’t only carrying species but creating new mobile ecosystems that sustain invasive species for extended periods and into previously untouchable waters.

Riding the Wave

“Plastic, particularly, has massively increased the transport possibilities in terms of how much flotsam there is, its variety (in size and structure), where it goes, and how long it floats for,” said David Barnes, a marine benthic ecologist at the British Antarctic Survey. “Furthermore, plastic can increase the local spread of invader species when they do arrive and establish.” One study found that 289 Japanese marine species were carried to distant shores on debris after Japan’s devastating 2011 tsunami. Another 455 non-native species have been found in the Mediterranean after hitchhiking through the Suez Canal, primarily on plastic waste.

In the Pacific, the South Pacific Gyre, a system of currents, carries waste from the Great Pacific Garbage patch, now containing 79,000 tons of plastic, to all corners of the ocean. Barnes has even found invasive species from plastic rafting in Antarctica, where experts previously thought freezing temperatures would deter such invaders. Barnes says these species are sometimes surviving for years on the high seas because the abundance of plastic isn’t just a mode of transport, but a new ecosystem that he deems the “plastisphere.”

Eva Blidberg, former project leader for Blastic, an EU plastic tracking initiative, says that the most effective way to stop the proliferation of invasive species is to “plug the marine litter tap.”

But it won’t be easy; much of this plastic is in international waters, and plastic produced in one country may end up thousands of miles away. Additionally, the COVID-19 pandemic caused a surge of plastic pollution from PPE, vaccines, and other medical waste, overwhelming waste systems worldwide. “A global problem like marine plastic litter, and all the challenges it creates, is impossible to solve without collaboration,” said Blidberg. Experts at the World Wildlife Fund say that the best way to do that is by extending producer responsibility for plastic waste and changing how our culture views single-use plastic.