30 Mar 2016

Japanese earthquake debris

From Nine To Noon, 9:38 am on 30 March 2016

Millions of tonnes of debris from Japan's devastating tsunami nearly five years ago are continuing to carry sea life thousands of kilometres across the ocean - and scientists warn they could wash up on New Zealand shores.

A magnitude nine earthquake triggered a massive wall of water that devastated Japan's north-east coast in 2011, killing almost 19,000 people and triggering a major nuclear accident.

The Japanese government estimates 75 percent of debris that was taken out to sea during the tsunami has sunk, but Jim Carlton from the Maritime Studies Program of Williams College and Mystic Seaport  told Nine to Noon there were hundreds of thousands of items still afloat - from small pieces of styrofoam to entire ships.

Mr Carlton, who is the lead principal investigator on Project ADRIFT's (Assessing the Debris Related Impact From Tsunami) biological diversity assessment team, said five Japanese skiffs had washed ashore in Oregon over the past couple of days and brought with them a range of marine life.

Previously entire concrete docks have been found on Oregon and Washington beaches, with buckets and other plastics regularly washing up on Hawaii and the North American coastline.

Mr Carlton said most of the debris from the tsunami was washing ashore on the Pacific North West Coast of America and Canada, carrying with it crabs, sea urchins, anenomes, fish, clams and other species.

Historically debris would have made from wood and would have decomposed at sea, but newer materials meant it was lasting much longer.

A key question for North America and Hawaii was whether some of 330 species found alive on the debris, could become invasive in the areas.

"It's given us one of our first real looks, in the history of marine biology, for long term survival of species rafting across an ocean," Mr Carlton said.

The debris has made a nearly 7000km journey across the ocean, most of it starting from north of Tokyo, but some has been picked up along the way.

Mr Carlton said the key concern was Japanese coastal species arriving alive on the other side of the ocean.

All of the objects that had washed ashore had tested negative for radioactivity.

Mr Carlton said it was very hard to predict the fate of any objects after the tsunami and know where they would end up.

"We know that certain things left the exact same port at the exact same time and yet have very different trajectories." 

It wasn't impossible that some debris - and marine life - could wash up on New Zealand shores.

"We think most of it's likely going to stay in the North Pacific, but things have surprised us quite a bit so far."

Listen to Jim Carlton on Nine to Noon: