A message in some bottles : ''Please take your litter home.........''

INACCESSIBLE ISLAND is well named. It is uninhabited rock in the South Atlantic ocean that belongs to Tristan da Cunha, a British dependency which itself vies with Easter Island for the honour of being the most remote inhabited place on the planet. Go there, though and you will find the coast covered with litter.

That, at least has been the experience of Peter Ryan of the University of Cape Town, in South Africa.

Since 1984 Dr. Ryan, an ornithologist, has been visiting Inaccessible and, along with his other studies, recording the litter stranded on the island's beaches. Just recently, in the  Proceedings of the National Academy of Sciences, he has published the results.

Though Inaccesssible is indeed remote, being near the South Atlantic's mid-point, the nature of  oceanic circulation means that this is exactly the sort of place where floating rubbish tends to accumulate - at the center of whirlpools thousands of kilometers across, called gyres.

Dr. Ryan's particular interest was where all the litter came from before it was swept into the gyre. And he found that this has changed a lot over the decades he has been visiting the island.

To impose some order on the question, he and his colleagues focused on one particular class of litter ; BOTTLES.

Their definition of a bottle included jars and aerosol containers, and encompassed things made of metal, glass or polymer. Most, though, were of polyethylene terephthalate, a light plastic, and had once held drinks.

A particular advantage of picking bottles to investigate is that they are often stamped with their country of manufacture. That enabled Dr. Ryan to analyze the history of oceanic littering.

He picked three recording points, corresponding to field trips to the island, and analysed the proportions of bottles from various geographical sources. In 1989 the preponderance of them [67%] was South Americans.

Twenty years later, in 2009, bottles made in Asia contributed more or less equally [44%] with South American ones [41%]. By 2018 the overwhelming majority [74%] were Asian.

This geographical shift speaks volumes. The first sample suggests that most litter arriving on  Inaccessible had been washed off the land or dropped from coastal shipping - South America being a relatively nearby continent.

The other two, with their rising proportion of trash from Asia, which is too far from the island for it to have floated there, strongly suggests that it was crews empties being flung from ocean-going vessels.

Such littering is banned by Annex V of the International Convention for the prevention of pollution from Ships - which, ironically, came into force in 1989, the year of Ryan's first survey. But evidently a lot of ships' captains do not care.

They permit the dumping of rubbish over the side, regardless. 

The World Students Society thanks ''The Economist''.


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