For most of the last decade, CSIRO scientists Denise Hardesty and Chris Wilcox have studied the worsening rubbish crisis in the world's oceans. Their research has estimated that nine out of 10 seabirds have ingested plastic – and predict almost all seabirds will have by 2050.
Their team has also surveyed Australia's entire coastline, finding most rubbish is our own.
The strongest predictor of rubbish levels was an area's level of disadvantage.Credit: Adam McLean
More recently, the scientists from CSIRO's Oceans and Atmosphere group have shifted their focus to land. "Rubbish doesn't start in the ocean, it has to get there somehow," says Dr Wilcox, a biologist turned statistician.
This week, the team released a report identifying the factors that drive rubbish levels across the Australian landscape, the first study of its kind. They found the strongest predictor of an area having a high amount of rubbish was its level of disadvantage. Neighbourhoods with low rates of education and employment had the highest risk of litter or illegally dumped rubbish.
Conversely, wealthy areas with considerable social advantage had the lowest risk.
The study also found locations where people are transient, such as highways, car parks and retail strips have greater amounts of rubbish than parks, residential areas and beaches.
Dr Hardesty says while the influence of socio-economics on rubbish levels makes sense, the strength of the relationship was surprising. An area's wealth or disadvantage had a 10 to 15 times stronger effect on rubbish levels than whether the area was a highway or car park.
Dr Hardesty hopes local and state governments will use the model to target interventions, such as clean ups, installing bins and community outreach, in areas where they will have the greatest impact.
NSW local councils spend more than $10 million removing illegally dumped rubbish each year.
The analysis relied on rubbish surveys by groups such as Keep Australia Beautiful, Clean Up Australia and the CSIRO, who collected data at more than 3000 sites around Australia between 2006 and 2016. The research, which was partly funded by the Australian Packaging Covenant, a partnership between the packaging industry and government, also incorporated census and land use data to determine the level of social disadvantage near rubbish sites, as well as their distance from roads and train stations.
The team found people littering was the main reason rubbish was found in the environment, followed by water and wind transportation. "For every piece of plastic dropped, about a fourth of the time that piece will get moved by water to a new location, and about an eighth of the time that piece of plastic will get blown somewhere else," Dr Wilcox says.
Erik van Sebille, an oceanographer at Imperial College London, who was not involved in the study, said reducing debris in the oceans – about 10 million tonnes of plastic enters oceans a year – required scientists and governments to know the main sources. "If it turns out that a large portion of land-based plastic enters the ocean via sewage systems, we can put effort into making these cleaner. Or if a lot of plastic comes from discarded wrappers and packaging, we need to control littering better," Dr van Sebille said.
The CSIRO team plans to collaborate with social scientists to understand people's behaviour around littering and illegal dumping.