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Acting on Plastic: How Seasonal Behaviour Dictates Plastic Pollution

All waste tells a story. A brief sift through landfills of the future—littered with robotic vacuums, fidgit spinners and medical-grade face masks—might be enough to tell future anthropologists all they need to know about how, for a moment, we once lived.


But unfortunately, the story plastic pollution tells is observable already. Plastic use in Australia is projected to double by 2040, with 130,000 tonnes already making its way into the marine environment. And as we’re now finding, this is just the tip of the polystyrene iceberg. Last year, CSIRO suggested there might be up to 14 million tonnes of microplastics (plastic of 5mm diameter or less) in the deep ocean – an amount that as it decays, will spread even further.

This swelling tide of plastic—far from being confined to landfill or recycling facilities—is a story dictated by our behaviour. With half the global population living within 100km of a coastline, our lifestyle and habits are written into the pollution in our waterways, bays and oceans.


Melbourne’s Port Phillip Bay, is a place where the story off plastic pollution is being told in dramatic detail. Despite being home to 43 threatened species, containing 4 nationally important aquatic ecosystems and being a recreational destination for huge local, interstate and overseas visitors, 2.5 billion litter items flow into the bay annually, with 2 billion (85%) of these being microplastics. According to the Port Phillip EcoCentre, plastic pollution in the Yarra river increased 400% between 2016 and 2017 and doubled again between 2018 and 2019.

But coming to grips with volume of plastic we’re creating is just the beginning. Two important questions follow: what are the key sources of this plastic torrent, and how is our behaviour influencing its spread?


Digging further into the Port Phillip EcoCentre’s 2020 Baykeeper report data, a couple of things become clear. Firstly, plastic pollution in both the Maribyrnong and the Yarra rivers—both of which flow into Port Phillip Bay—peaks in summer. In the Yarra river, plastic pollution more than doubles in summer compared to winter, with the summer litter items are between four and five times the amount of litter in autumn. While some of this disparity may be attributed to higher water flows in cooler months sweeping plastics straight out to the bay, it also illustrates how increased human activity around our waterways and coast is very much tied to the amount of observable plastic pollution in our rivers and bay. The Maribyrnong by contrast, has less seasonal dispartity and a higher spring litter count, which the report attributes to the river’s proximity to the Flemington Racecourse, a key spring racing venue.

Secondly, apart from fragments of hard plastic, often crushed or decayed plastic bottles, which make up the bulk of what is found in both rivers, the remainder are led by other recognisable consumer items: polystyrene and soft plastics – some telltale signs of summer, where visitors come and go, but traces of their holidays remain.


Legislative interventions, like the Victorian Labor Government’s plan to phase out single-use plastics by 2023, or technological innovations, like redesigning packaging materials, are essential. However, an arguably stronger and more permanent driver of change, lies in the alteration of behaviour. Interestingly, despite both polystyrene cups and soft plastics being among some of the highest volume litter items found in both the Yarra and Maribyrnong rivers, the Baykeeper report found a distinctly lower amount of plastic straws. In fact, despite plastic straws still being both lawfully available and technologically, still made of plastic, straws were in steady decline, and have been for a few years, as stores and consumers have moved away from them.

But while ‘moving away’ from plastic sounds simple, there are a complex string of motivators that need to be tapped into to truly change even a seemingly simple behaviour, like giving up largely redundant items such as plastic straws. Kim Borg, a research officer at BehaviourWorks in the Sustainable Development Institute writes, in an article for the Conversation, that awareness alone is unlikely to shift behaviour. Though awareness plays a critical role, converting an initially niche idea or solution, into a social norm. Borg writes: “Successful behaviour change campaigns must empower individuals. We should be left feeling capable of changing, that changing our behaviour will impact the problem, and that we are not alone”.


But as consumers, behaviour is often dictated by the options presented to them, by what is acceptable and convenient. Changing the default is a challenge often taken up by a psychological discipline known as ‘behavioural economics’, which studies the psychological, emotional, and social factors that make up peoples’ decision making. Central to the behavioural economics canon, is a book by American economist Richard Thaler, called ‘Nudge’. According to Thaler and Sunstein, a nudge is “any aspect of the choice architecture that alters people’s behavior in a predictable way without forbidding any options or significantly changing their economic incentives”. In other words, nudges don’t prohibit or restrict choice, they guide it.

Plastic bags provide a good case study for nudging. In her research, Borg writes about Ireland’s ‘Plastax”—their tax on plastic bags—which didn’t prohibit plastic bags, but simply disincentivised it, reducing plastic bag use by 90%. Japan also managed to reduce plastic bag use by 40% by changing almost nothing. The simple act of cashiers asking if people wanted a plastic bag instead of freely giving them out, reduced their use by almost half. This reconsideration of the default is important when it comes to plastics, because it wouldn’t be outrageous to suggest that most single-use plastic consumption is unnecessary – just unconscious byproducts of a wasteful default state.


So what does this mean for our local plastic problem – for the 2,455,603,200 litter items that flow into Port Phillip Bay annually? Firstly it highlights the importance of public awareness in changing perception. Making clearer the seasonal and geographic links between our behaviour and the amount of plastic choking our waterways is critical. In the Port Phillip EcoCentre’s Baykeeper study, geography also plays into activity, and by extension, the volume of plastic pollution at particular sites. The Maribyrnong for example, experiences a proportionally higher level of pollution during the spring because of the river’s proximity to Flemington Racecourse. Likewise, in summer the Yarra river parklands are used extensively for recreation and tourism during the peak of summer. Other, less seasonal locations of recreational activity also play a role. The study also highlights the Calder Raceway, located in the vicinity of Jacksons Creek, not far upstream from where the creek joins the Maribyrnong river. It’s crucial that awareness targets both seasonal recreational activities and areas of high visitation – where litter is most likely to accumulate. Making stronger, targeted linkages between our activities and the rise in plastic pollution is important in grounding the problem in the real lives of residents.


Though a focus on the geography of how we recreate isn’t the only way awareness campaigns could help drive further behaviour change. Marine scientists from the University of Hull also have a few ideas, including swaps from plastics to environmentally conscious choices, sharing or borrowing items instead of buying them, and the big one: taking your waste with you.

However, these marine scientists also consider something that has eluded many plastic campaigns to date, and is sorely missing from public awareness around single-use plastic consumption, which is changing the way we think about plastic and cleanliness. The prepackaging of fresh goods as a form of cleanliness is largely a perception – a social norm. Even COVID 19 survives longer on plastic than it does on porous surfaces. The fact of the matter is that plastic isn’t clean, and creating a stronger association between plastic and the visible pollution it causes in the biosphere, might just be the kind of ‘nudge’ that we need to start moving away from it for good. Plastic Oceans Australasia’s ‘Picnics Unwrapped’ campaign delivers just such a nudge, allowing people to see exactly what a ‘clean’ picnic really looks like and showing that you don’t have to bring plastics to a picnic in order to have a good time.


Australia’s National Plastics Plan, as well as the Victorian government’s goal of banning specific single-use plastics, is a good start. But awareness and change around behaviour is for good, outlasting both political change and technological advance. Plastic use is projected to increase, with marine plastic pollution expected to triple by 2040, to 29 million metric tonnes. And with microplastics become increasingly widespread, technological and legislative support will be essential, but it must be underpinned by a change in our behaviour towards single-use plastic. And if we want to continue enjoying the rivers and beaches we love so much, we have to start changing now.


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