en-fr  How an Uninhabited Island Got the World’s Highest Density of Trash
Comment une île déserte a été affectée de la densité d'ordures la plus élevée.

L'isolement protège l'île de l'ingérence humaine... mais pas de 18 tonnes de plastique.

38 millions de morceaux de déchets de plastique recouvrent cette île éloignée.

Par Laura Parker du National Geographic.

Publié le 17 mai 2017.

L'île Henderson se trouve dans le Pacifique Sud, à mi-chemin entre la Nouvelle-Zélande et le Chili. Personne n'y vit. Elle est à peu près aussi loin de n'importe où et de n'importe qui sur Terre.

Pourtant, sur les plages de sable blanc d'Henderson, vous pouvez trouver des articles en provenance de Russie, des États-Unis, d'Europe, d'Amérique du Sud, du Japon et de Chine. Ce sont tous des déchets, la plupart en plastique. Tout cela traverse en flottant les mers du monde jusqu'à être balayé dans le tourbillon du Pacifique Sud, un courant circulaire océanique qui fonctionne comme un tapis roulant, en rassemblant les débris de plastique et en les déposant sur le rivage de la minuscule Henderson à raison d'environ 3 500 morceaux par jour.

Jennifer Lavers, co-auteure d'une nouvelle étude sur cette accumulation de 38 millions d'éléments, a dit à l'Associated Press qu'elle avait trouvé la quantité "vraiment alarmante". Un grand nombre de déchets sont constitués de filets et de flotteurs de pêche, de bouteilles d'eau, de casques et de vastes morceaux rectangulaires. Deux tiers des ordures sont invisibles au premier abord parce qu'ils sont enfouis à environ quatre pouces (10 cms) de profondeur sur le rivage.

"Bien qu'inquiétants, ces chiffres sous-estiment la véritable quantité de débris, parce que des éléments sont enterrés 10 cms sous la surface et que les particules de moins de 2mm et les débris le long des zones de falaises et des côtes rocheuses ne peuvent pas être répertoriés," précisent Lavers et son collègue dans leur étude publiée mardi dans la revue scientifique Proceedings de la National Academy of Sciences.

L'accumulation est même plus inquiétante si l'on conidère qu'Henderson est un site du patrimoine mondial des Nations Unies et l'une des plus importantes réserves marines du monde. Le site internet de l'UNESCO qualifie Henderson de "joyau" et de "l'un meilleurs exemples restants au monde d'atoll coralien," qui est pratiquement préservé de la présence humaine." Henderson est l'une des quatre îles de l'archipel de Pitcairn, groupe de petites îles dont l'homonyme est réputé pour être la patrie des descendants des mutinés du HMS Bounty. La population de Pitcairn qui est réduite à 42 personne, utilise Henderson comme lieu d'escapade idyllique pour fuir la vie de tous les jours à Pitcairn. Mais en dehors de la proximité des habitants de Pitcairn, des scientifiques occasionnels, et des arrivages de touristes faisant leur traversée de deux jours à la voile depuis les îles Gambier, Henderson n'abrite que quatre sortes d'oiseaux terrestres, dix sortes de plantes, et une grande colonie d'oiseaux marins.

Lavers, une scientifique de l'Australia University de Tasmanie, et son co-auteur, Alexander Bond, un biologiste de la conservation, sont arrivés sur Henderson en 2015 pour un séjour de trois mois. Ils ont mesuré la densité des déchets et ont collecté pres de 55 000 morceaux de détritus, sur une centaine desquels on pouvait retracer le pays d'origine. Les analyses des deux ont conclu que près de 18 tonnes de plastique avaient été accumulées sur l'île, donnant à Henderson la plus haute densité de débris plastiques jamais enregistrée au monde, au moins jusque là.

Jenna Jambeck, professeur* d'ingénierie environnementale à l'université de Georgia, qui a été l'une des premières scientifiques à mesurer la pollution par les déchets des océans sur une échelle globale, n'a pas été surprise que Lavers et Bond aient découvert du plastique dans une telle abondance sur Henderson.* L'étude de Jambeck de 2015 a conclu que 8 millions de tonnes d'ordures flottaient sur l'océan chaque année, assez pour remplir cinq sacs de supermarché sur chaque distance d'un pied (33 cm) de toutes les côtes de la terre.

“One of the most striking moments to me while working in the field was when I was in the Canary Islands, watching microplastic being brought onto the shore with each wave,” she says. “There was an overwhelming moment of ‘what are we doing?’ It’s like the ocean is spitting this plastic back at us. So I understand when you’re there on the beach on Henderson, it’s shocking to see.” The Henderson research ranks with earlier discoveries of microplastics in places so remote, such as embedded in the deep ocean floor or in Arctic sea ice, that finding plastic in such abundance touched a nerve.

“People are always surprised to find trash in what’s supposed to be an uninhabited paradise island. It does not fit our mental paradigms, and this might be the reason why it continues to be shocking,” says Enric Sala, a marine scientist who led a National Geographic Pristine Seas expedition to the Pitcairn Islands, including Henderson, in 2012. “There are no remote islands anymore. We have turned the ocean into plastic soup.

Laura Parker is a staff writer who specializes in covering climate change and marine environments.
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How an Uninhabited Island Got the World’s Highest Density of Trash.
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Isolation protects the island from human intrusion—but not 18 tons of plastic.
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38 Million pieces of plastic trash cover this remote island.
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By Laura Parker, National Geographic.
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Published may 17, 2017.
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Henderson Island lies in the South Pacific, halfway between New Zealand and Chile.
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No one lives there.
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It is about as far away from anywhere and anyone on Earth.
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All of it is trash, most of it plastic.
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“There are no remote islands anymore.
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We have turned the ocean into plastic soup.
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How an Uninhabited Island Got the World’s Highest Density of Trash.

Isolation protects the island from human intrusion—but not 18 tons of plastic.

38 Million pieces of plastic trash cover this remote island.

By Laura Parker, National Geographic.

Published may 17, 2017.

Henderson Island lies in the South Pacific, halfway between New Zealand and Chile. No one lives there. It is about as far away from anywhere and anyone on Earth.

Yet, on Henderson’s white sandy beaches, you can find articles from Russia, the United States, Europe, South America, Japan, and China. All of it is trash, most of it plastic. It bobbed across global seas until it was swept into the South Pacific gyre, a circular ocean current that functions like a conveyor belt, collecting plastic trash and depositing it onto tiny Henderson’s shore at a rate of about 3,500 pieces a day.

Jennifer Lavers, co-author of a new study of this 38-million-piece accumulation, told the Associated Press she found the quantity “truly alarming.”

Much of the trash consists of fishing nets and floats, water bottles, helmets, and large, rectangular pieces. Two-thirds of it was invisible at first because it was buried about four inches (10 cm) deep on the beach.

“Although alarming, these values underestimate the true amount of debris, because items buried 10 cm below the surface and particles less than 2 mm and debris along cliff areas and rocky coastlines could not be sampled,” Lavers and a colleague wrote in their study, published Tuesday in the scientific journal, Proceedings of the National Academy of Sciences.

The accumulation is even more disturbing when considering that Henderson is also a United Nations World Heritage site and one of the world’s biggest marine reserves. The UNESCO website describes Henderson as “a gem” and “one of the world’s best remaining examples of a coral atoll,” that is “practically untouched by human presence.”

Henderson is one of the four-island Pitcairn Group, a cluster of small islands whose namesake is famed as the home to the descendants of the HMS Bounty’s mutineers. Pitcairn’s population, which has dwindled to 42 people, uses Henderson as an idyllic get-away from the day-to-day life on Pitcairn. But aside from the neighboring Pitcairners, the occasional scientist or boatload of tourists making the two-day sail from the Gambier Islands, Henderson supports only four kinds of land birds, ten kinds of plants, and a large colony of seabirds.

Lavers, a scientist at Australia’s University of Tasmania, and her co-author, Alexander Bond, a conservation biologist, arrived on Henderson in 2015 for a three-month stay. They measured the density of debris and collected nearly 55,000 pieces of trash, of which about 100 could be traced back to their country of origin. The duo’s analysis concluded that nearly 18 tons of plastic had piled up on the island—giving Henderson the highest density of plastic debris recorded anywhere in the world—at least so far.

Jenna Jambeck, a University of Georgia environmental engineering professor, who was one of the first scientists to quantify ocean trash on a global scale, was not surprised that Lavers and Bond discovered plastic in such abundance on Henderson. Jambeck’s 2015 study concluded that 8 million tons of trash flow into the ocean every year, enough to fill five grocery store shopping bags for every foot of coastline on Earth.

“One of the most striking moments to me while working in the field was when I was in the Canary Islands, watching microplastic being brought onto the shore with each wave,” she says. “There was an overwhelming moment of ‘what are we doing?’ It’s like the ocean is spitting this plastic back at us. So I understand when you’re there on the beach on Henderson, it’s shocking to see.”

The Henderson research ranks with earlier discoveries of microplastics in places so remote, such as embedded in the deep ocean floor or in Arctic sea ice, that finding plastic in such abundance touched a nerve.

“People are always surprised to find trash in what’s supposed to be an uninhabited paradise island. It does not fit our mental paradigms, and this might be the reason why it continues to be shocking,” says Enric Sala, a marine scientist who led a National Geographic Pristine Seas expedition to the Pitcairn Islands, including Henderson, in 2012. “There are no remote islands anymore. We have turned the ocean into plastic soup.

Laura Parker is a staff writer who specializes in covering climate change and marine environments.