Cities deliver plastics to rivers

New study aims to define what plastics are getting into our rivers and how to stop them at source.

A new research project on plastic rubbish in waterways is set to investigate the role of New Zealand rivers in transporting damaging plastics to the sea.

The three-year study, run by NIWA scientist Dr Amanda Valois, will analyse plastic waste in Wellington's Kaiwharawhara catchment to ascertain how it is entering our fresh water — and how it can be stopped.

Valois was inspired to start the research project by the work of the Sustainable Coastlines organisation, which coordinates large-scale coastal clean-up events.

"A lot of what they collect on our beaches is plastic, especially single-use plastic," she says. "But cleaning up this waste by the time it's got to the sea is a very inefficient way of dealing with it."

Rather than being the 'ambulance at the bottom of the cliff', Valois wants to find out where it's coming from — and find ways to stop it. She applied to the Ministry of Business, Innovation and Employment's Endeavour Fund through its 'Smart Ideas' mechanism, to look at ways to stop plastic pollution at an earlier stage in the cycle.

"Most of the focus has been on the marine system but we want to see what role rivers play in carrying plastic waster into the ocean," she says.

The Kaiwharawhara stream system begins in Karori, then wends its way through the city's western suburbs and down the Ngaio Gorge, before discharging into Wellington Harbour.

"We chose Kaiwharawhara because it is a relatively small catchment so it's manageable to track the different plastic sources and it's also very diverse," Dr Valois says. "It starts off with pristine headwaters in the Zealandia sanctuary but, by the time it weaves its way through the city and gets to the harbour, it's quite polluted. It's a way to see how plastics accumulate across a diverse landscape."

While many people think the biggest problem with plastic pollution in waterways is aesthetics — it just looks bad — Valois says it has a much greater effect.

"You get plastic wrapping around fish and eels eating it and organisms choking on it or getting stuck in plastic bottles, so it's harming our wildlife; it has an effect on human health as well. We have been looking at ACC reports of people hurt by plastics in the water. When I go into the streams now I always wear water shoes just in case; I think that's sad."

Another issue is microplastics — tiny pieces of plastic either from products containing microbeads, or broken down from larger pieces — which may enter the food chain through aquatic animals.

Kaiwharawhara was chosen because Wellington's steep topography and regular rain and wind means plenty of plastic refuse finds its way into the stream.

That's a phenomenon that Valois says challenges the 'out of sight, out of mind' mindset of even the best recyclers.

"People are good at putting their recycling bins out, filled with plastic, but on a windy day you often see that plastic being blown out and onto the side of the road, and into the river," she says. "Once it leaves their yard, people tend to think it's someone else's problem. But it's a big problem, both in the river and then in the ocean.

Valois will not be alone picking through the detritus — she leads a team of six scientists working on the project, and is working alongside eight research, community and iwi organisations to gather and analyse the refuse.

"We are working closely with community groups and schools and people who live in the area. A lot of rubbish collection has been going on in the catchment already, so we are going to harness that energy to start collecting it in a more exact monitoring way and quantifying it."

Valois says the overall aim of the project is to develop standardised methods to find out where the plastic is coming from, how much and what types.

"Once we figure out what are the most significant plastic types, we can work with communities to reduce them. We've seen the arbitrary banning of microbeads and plastic bags but we don't know what the other sources of plastic are – so that will provide the best bang for our bucks to reduce them."

Following the three-year gathering and analysis project, Valois and her team intend to widen their reach: "In five years' time, if our monitoring and efforts to reduce plastics have worked, we hope what we have found out can be applied to catchments around New Zealand."

*Keep track of the project — including its more unusual finds — through Twitter (@what_fish_eat).