There is now so much ocean plastic that it has become a route for invasive species, threatening native animals with extinction
Japan’s 2011 tsunami was catastrophic, killing nearly 16,000 people, destroying homes and infrastructure, and sweeping an estimated 5m tons of debris out to sea.
That debris did not disappear, however. Some of it drifted all the way across the Pacific, reaching the shores of Hawaii, Alaska and California – and with it came hitchhikers.
Nearly 300 different non-native species caught a lift across the ocean in what can be thought of as a “mass rafting” event. The Smithsonian Environmental Research Center in 2017 counted 289 Japanese marine species that were carried to distant shores after the tsunami, including sea snails, sea anemones and isopods, a type of crustacean.
Plastic rafting poses a huge and mostly unknown danger. Invasive species that ride plastic litter to new shores can reduce habitats for native species, carry disease (micro-algae is a particular threat), and put further strain on ecosystems already pressured by overfishing and pollution. According to David Barnes, marine benthic ecologist at the British Antarctic Survey and visiting lecturer at Cambridge University, rafting increases “extinction risk [while] reducing biodiversity, ecosystem function and resilience”.
The tsunami also showed something new: many of the animals survived more than six years adrift, longer than previously thought possible.
Rafting – or oceanic dispersal – is a natural phenomenon. Marine organisms attach themselves to marine litter and travel hundreds of kilometres. Free-floating clumps of seaweed such as sargassum, sometimes 3 metres thick, provides a home for certain “rafting species” in the Atlantic, such as reef fish, or pipefishes and seahorses, which are both poor swimmers.
Plastic rafting poses a huge and mostly unknown danger. Invasive species that ride plastic litter to new shores can reduce habitats for native species, carry disease (micro-algae is a particular threat), and put further strain on ecosystems already pressured by overfishing and pollution. According to David Barnes, marine benthic ecologist at the British Antarctic Survey and visiting lecturer at Cambridge University, rafting increases “extinction risk [while] reducing biodiversity, ecosystem function and resilience”.
The tsunami also showed something new: many of the animals survived more than six years adrift, longer than previously thought possible.
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