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No dumping here please

Question:

Where is the biggest rubbish dump on the planet? If you thought Europe, America or China you'd be wrong! In fact, the biggest rubbish dumps are not actually in any country at all.

Answer:

Believe it or not, they are at sea!

Disposing of the Titanic - no problem!

Hull of the titanic

People have been dumping garbage into the oceans for hundreds of years. The seas are packed with bacteria and algae that will eat away quite happily on almost anything organic: sewage, bones or wood. The oceans can even dispose of whole ships.

The Titanic sank in 1912 and even the steel hull is being eaten by rusticles, and that's in less than a hundred years! Up until the mid-20th century the seas could easily break down anything people dumped into it.

Titanic

Why is dumping a problem now?

The problem is plastics. On the plus side, plastics are fantastic, indispensible materials. They can be hard, soft, elastic or rigid. If you need a material to do a job, then plastic is your man. And boy do they last...and last...and last...­ This can be a real advantage: you definitely wouldn't want the plastic hull of your boat to disintegrate after a few months at sea.

The trouble is that an enormous amount of plastic waste finds its way into the oceans. You only have to have a walk along the coast anywhere in the UK, in fact just about anywhere in the world, to see masses of plastic debris washed up. The bits we see washed up are just a tiny fraction of what's out there.

Where does it all go?

Until recently we didn't know; scientists are only now starting to piece the information together.

Clue 1

We know that there are great currents moving through the oceans. The most famous is the North Atlantic Conveyer that moves warm water from the tropics past the coast of Britain. It would be as cold as Moscow in Britain without it with winter temperatures dipping below -30C and deep snow for four months of the year.

Clue 2

Along with all the warm water, the Conveyor also brings pieces of coral, coconuts and chocolate wrappers from the Caribbean. The next time you walk along a beach, think about where all the debris came from. Lots of it will have travelled thousands of miles.

Clue 3: rubber duck researchers

In 1992, a container full of bright yellow ducks (and beavers and frogs!) escaped from a cargo ship in the middle of the Pacific Ocean. Nearly 29,000 of them spilled into the sea. It wasn't long before rubber ducks started turning up all over the place.

Ducks

Timeline:

  • 10 months: Alaska
  • 3 years: Japan and Hawaii
  • 8 years: the arctic ice near the North Pole
  • 15 years: UK coast line

Clue 4: duck flotilla, Gyres and garbage patches

There are two main currents in the Pacific: the Subtropical Gyre and the Sub Polar Gyre. By tracking the duck flotilla it is possible to look at the way ocean currents move around the globe.


What's a gyre?

A gyre is anything with a circular path; it's where the word gyration comes from. It takes about 2.9 years for a rubber duck (or anything else!) to go around the gyre once.

The polar garbage patch

Where did this figure come from? - Message in a bottle

This figure was confirmed by dropping 33,868 messages in brown beer bottles into the sea off Alaska and waiting for people to find them and respond.

Clue 5: The Great Pacific Garbage Patch

One of the effects of the Subtropical Gyre is that there is a calm patch where lots of debris tends to gather. It is a bit like the 'eye' of a hurricane where the air is still and all the rest revolves around it. This turns out to be just about the biggest rubbish dump on earth. It is known as the Great Pacific Garbage Patch. It contains mostly plastic fragments about the size of a cornflake. These are the remains of much larger debris that has been smashed up by the wind and the waves. Over 10,000 containers per year are lost overboard from ships - so there is a lot of stuff out there.

Clue 6: trawling nets

Trawling Nets

It has only recently been discovered just how much stuff is out there! Scientists have been monitoring the patch for several years by trawling a net through the top metre of the water and counting the pieces of debris. What has only just been realised is that if you trawl at a lower depth you still pick up lots of debris.

Scientists now think that there is far more rubbish out there than we thought! Far more lies just below the surface and is of very nearly neutral buoyancy. The waves stir the water up just enough to keep it out of sight at a depth of 1 to 10 m.

The garbage patch covers a staggering area: about 3.5 million Km2: about 17 times the area of Britain! Each square Km contains at least 20,000 pieces of rubbish. Each piece weighs about 0.15g. So the total mass of trash out there is at least 10.5 million Kg.

Dead zone garbage patches

There are lots more garbage patches out there, but they haven't been well studied. Computer simulations suggest that there may be many of these dead zones where rubbish goes in and never comes out.

Will the bits ever be destroyed?

Eventually, yes. Plastic does not degrade by being eaten by bacteria like normal waste. Even oil slicks are sooner or later disposed of by bugs. Plastic does decompose under the influence of Ultra Violet light. Ultimately the sun will reduce it to its component molecules and it will be gone. But this may take a while, a long, long while.

What effect does it have on the marine environment?

The truth is that we don't really know. We do know that many animals eat these bits by mistake. The true impact is for the next generation of researchers to discover.

The big questions:

What happens to all the rubbish that is thrown into the oceans?

Do plastics disappear over time?

Should we stop rubbish being dumped into the oceans?

Is the rubbish in the oceans harmful to wildlife?

How much rubbish is in the oceans?