Environmentalist tells of the dangers of plastic waste adrift in the ocean

The great "Pacific garbage patch" is a huge island of plastic debris floating in the middle of the ocean. At least, that's what many of us have been led to believe. The truth is there is no dense mass of discarded plastic out there - but the reality is far more troubling.

By the time most plastic reaches one of the world's five great oceanic gyres - massive current systems that flow in a circle - it has been reduced to micro particles. You could sail through one of these patches - six have been identified so far - and not even know it. But the long-term effect of all this plastic is still being evaluated.

Dr Marcus Eriksen is at the forefront of this research. Together with his wife, Anna Cummins, he founded 5 Gyres, an NGO dedicated to researching plastic pollution and raising awareness about the problem. They have trawled the surface of the world's oceans, sifted through the debris and come up with a figure for the amount of plastic already dumped into our oceans - 1.76 million tonnes.

That's a lot of plastic and most of it is not visible. As the material is carried out to sea, it degrades, the sun and waves reducing it to smaller and smaller pieces. This is not news. The first report on micro-plastic particles in the oceans was published in the 1960s, and research reports followed in the 1970s. It wasn't until 1997 that the story caught the public's attention.

Charles Moore, a surfer, scientific researcher and racing boat captain, was returning from a sailing race when he noticed an area in the Pacific Ocean strewn with floating plastic debris. He reported his finding, describing a massive expanse twice the size of Texas. From there, the myth of the island of plastic was created, but at least the issue was on the public radar.

"I'm not sure it would have been noticed if it hadn't been sensationalised," says Eriksen, who was in town last week to speak at the Plastic Free Seas Youth Conference, the first of its kind in Hong Kong.