UNSW Research Maps Marine Plastic Pollution Sources Along NSW Coast

The study (read here), published in Marine Pollution Bulletin, is the first to combine oceanographic modeling with over a decade of citizen science data to provide insights into how marine debris (particularly plastics) move through coastal waters in New South Wales. 

The research is a collaborative effort between physical oceanographers from the UNSW Coastal and Regional Oceanography Lab at UNSW's School of Biological, Earth and Environmental Sciences and the UNSW Centre for Sustainable Development Reform, using data from the largest citizen science database on marine debris in the southern hemisphere: the Australian Marine Debris Initiative (AMDI), hosted by Tangaroa Blue Foundation.

"We used data collected by citizen scientists on Australian beaches to inform our oceanographic modelling so we could identify the likely origins of the debris," explains lead author Dr. Claudia Gaby Mayorga Adame. "What we found was surprising – 50% of plastic debris returns to shore within just 8 days."

Key Findings and Implications 

These findings indicate that most plastic debris found on beaches in southeastern Australia originates from nearby sources. The debris travelled, on average, less than 20 kilometres (the distance from Maroubra Beach to Taronga Zoo). 

This is consistent with 10 years of surveys of marine debris surveys across Australia, which revealed that at least half of all marine debris sampled on beaches could directly be linked to land-based sources (Gacutan et al., 2022).

Most studies that model marine debris often do not use data of direct observations and instead rely on assumptions. When the team compared two modelling approaches – one informed by observations and the other without – the observational data clearly altered findings and provided more accurate and actionable insights.

Researchers identified a single ‘accumulation zone’ between Sydney and Newcastle where debris is likely to accumulate. "By using actual debris data collected by volunteers through the Australian Marine Debris Initiative, we could pinpoint a priority area that could become the target for management efforts," explains co-author Dr. Jordan Gacutan. "This contrasts with models that haven’t used empirical data – which suggested multiple hotspots along the coast."

"For NSW, these findings are particularly significant," notes co-author Professor Moninya Roughan. "The ocean current patterns we've mapped suggest that nearly all waste on NSW beaches comes from local littering and dumping, with minimal contribution from other regions. This means local actions can have a real impact on reducing beach pollution."

What's next?

Understanding the origins of marine debris and pollution can inform efficient and evidence-based management strategies.

1. Local actions can have a big impact
   
   Finding that 50% of debris likely arises from local sources means that local clean-up and prevention efforts can have measurable impacts.
   
   This also challenges the perception that majority of marine debris arises from offshore or far away sources and is ‘someone else’s responsibility’.
   
   
2. Targeted activities
   Clean-ups organised by local council and civil society can focus efforts on the likely ‘accumulation zones’ where debris is likely to be released into the environment.
   
   
3. Improved prevention
   
   Local governments can focus on improving waste management infrastructure and services in coastal and estuarine areas.
   
   Education and behaviour change programs can be targeted at communities near estuarine and coastal areas.
   
   Citizen science data can be used inform management decision-making and evaluate policy effectiveness.
   
   
4. The importance of data for evidence-based management of marine pollution
   
   Data on plastic are crucial to understanding the scale of the problem, make evidence-based decisions and track the effectiveness of management efforts over time. Despite its importance, data on plastic are extremely difficult to collect, store and manage.
   
   By demonstrating how citizen science data can enhance scientific models to provide more accurate, practical insights, this research demonstrates how citizen science could be a key player in fulfilling national data gaps.

"Our research demonstrates how combining citizen science data with broader oceanographic modelling can inform more effective interventions," adds Dr. Mayorga Adame. "This integrated approach provides the realistic information needed to develop targeted solutions to address plastic pollution."

This work is a contribution to Australian Research Council Discovery Project DP230100505 and was supported by the UNSW Translational Impact Seed Fund and in-kind by the Global Ocean Accounts Partnership Secretariat.