It's likely that plastic trash is an emerging threat to Auckland's famous harbour, though at present this can't be backed up by much hard data.

Tiny pieces of plastic in the water may well be reducing fish stocks, killing off marine mammals and sea birds and leaching dangerous toxins into once rich kaimoana beds.

Perhaps, unless we launch a massive public education campaign, the scale of this pollution will one day cause tourism-killing coverage in foreign media.

But there's little to quantify the extent of the plastics polluting New Zealand's most important harbour.

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Following several days of ringing around, I still couldn't establish how many tonnes of this waste is deposited in the Waitemata annually, how much gets washed ashore, versus remaining in the water column, or sand; or how much is ingested by fish and sea birds.

We don't have an estimate of the quantum of chemicals it generates either.

It's as if all we can really say is, "yeah, probably heaps bro".

However, even if the exact size and scale has not yet been established, some excellent people are already fighting the problem.

The Watercare Harbour Clean-up Trust has removed 120 shipping containers of trash from beaches, estuaries and mangroves around the harbour over the last 10 years.
Other NGOs have accounted for vast amounts of trash and so have cumulative efforts of private citizens who clean up their own beach front.

Not all unsightly rubbish collected off the beach is plastic, Watercare trust chairman Peter Drummond points out that his volunteers pick diverse trash on the shoreline, including old tyres, household appliances, car batteries and lumps of concrete.

Yet repulsive as this refuse is, it's plastics that are causing greatest concern.

Having plastic in our waters isn't unusual by world standards - right across the Pacific there's massive problem.

But the plastics in the Waitemata overwhelmingly come from Auckland, rather than elsewhere.

When Sustainable Coastlines cleans up the Great Barrier shoreline, the east side (facing Chile) is relatively clean, while parts of the west coast (facing Auckland) get festooned with tonnes of plastics because of the prevailing wind bringing it from the city.

New Zealand's entire west coast - all the way to Stewart Island - is affected by plastic waste from international sources.

Sustainable Coastlines has picked up well over 100 tonnes of plastic rubbish in the past three years.

Food wrappers, foam packaging, plastic bags and drink bottle caps are the main offenders - all single-use, disposable plastic products.

These products devastate marine life. Colonies of Black Backed Gulls nest amongst piles of rubbish on Auckland's Rangitoto Island. Pied Shags get wrapped in plastic, little blue penguins are strangled by a plastic bottle rings on Great Barrier and turtles have washed up dead in the Hauraki Gulf with plastic in their guts.

What's the answer?

The overwhelming majority of this waste is generated by Aucklanders.
For some reason we all feel free to drop our plastic waste on the ground, for it to wash via drains and rivers into our beautiful harbour.

So in my view the solution must be two-fold:
First, establish a best estimate of the Waitemata Harbour's plastic pollution problem; how fast it is growing and where it's likely headed.

Next, on the basis of hard data collected, fund a HUGE public education campaign.
Only action on the scale taken to curb smoking and drink-driving is likely to succeed.
But at this point, to get the kind of money required, we'll need to go the politicians armed with additional facts.

That's just my view, send yours (in a few words) to - paul.charman@nzme.co.nz
To get involved, contact Sustainable Coastlines - www.sustainablecoastlines.org
or the Watercare Harbour Clean-up Trust - www.watercare.co.nz/community/cleanup-trust