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Stills of ROV footage show litter accumulations at the bottom of the Messina Strait [Courtesy of Nature.com]

New Zealand: Climate change erosion feeding deep ocean trash dump

Coastal erosion carries millions of tonnes of long-buried trash into deep ocean canyons, where it remains for decades.

There are growing concerns that increasing coastal and river-bank erosion is carrying millions of tonnes of long-buried rubbish into deep ocean canyons, where toxic waste and plastics will remain for decades.

The warning comes after heavy flooding on the West Coast of New Zealand's South Island washed part of a disused landfill into the ocean on March 26, scattering thousands of tonnes of plastic along 50km of normally pristine coastline.

The once in a hundred years flood - which saw 1,000mm of rain fall in less than 48 hours - is believed to have swept thousands more tonnes of trash out to sea, depositing some of it into a 4km-deep underwater canyon off the coast.

"We know rubbish has ended up along a wide stretch of the coastline," Joshu Mountjoy, a marine geoscientist at New Zealand's National Institute of Water and Atmospheric Research, told Al Jazeera.

"It is likely that a component of the Fox River landfill waste will end up out of sight in the deep ocean by the same processes."

Flooding washed part of the disused Fox River landfill into the ocean [South Westland Coastal Cleanup/Facebook

Marine litter is known to have a major impact on marine life. Plastics can be especially insidious as they break down to microplastics that can be ingested.

"Submarine canyons are exceptional environments for focusing marine life and can be badly impacted," said Mountjoy.

Along with plastics, toxic materials from the waste can also be incorporated into the food chain.

"Fish can absorb toxic substances in waste [and] store it in their bodies," Jeff Seadon, a Built Environment engineer at Auckland University of Technology, told Al Jazeera.

"These substances proceed up the food chain till humans eat the fish and we can absorb those chemicals, which can affect our health."

Global issue

As climate change results in more extreme weather events and sea level rise, there are fears similar flooding could see many more landfills around the world exposed in the same way.

Last month, the United Nations Environment Programme published a report looking into waste management practices in Small Island Developing States.

It identified coastal dumpsites and those close to rivers as a major issue.

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