Imma Perfetto
Cosmos science journalist
New satellite technology might help to measure the extent of the global plastic pollution crisis by better detecting plastics washed up on remote beaches.
The technology, which has been successfully field tested on a remote stretch of Australian coastline, distinguishes the differences in reflection of infrared light by sand, water, and plastic.
An estimated 19 to 23 million tonnes of plastics enter marine and coastal environments each year which is projected to more than double by 2030. The new tool could be an effective way to monitor plastic pollution so it can be more easily accessed and removed by clean-up operations.
“Remote island beaches have some of the highest recorded densities of plastics in the world,” says Dr Jenna Guffogg, who led the study as part of her joint PhD research at RMIT University in Australia and the University of Twente in the Netherlands.
“And we’re also seeing increasing volumes of plastics and derelict fishing gear on the remote shorelines of northern Australia.”
This plastic, she says, can have severe impacts on wildlife and their habitats.
“Plastics can be mistaken for food, larger animals become entangled and smaller ones, like hermit crabs, become trapped inside items such as plastic containers.”
Plastics fragment further into micro and nano plastics.
“While the impacts of these ocean plastics on the environment, fishing and tourism are well documented, methods for measuring the exact scale of the issue or targeting clean-up operations, sometimes most needed in remote locations, have been held back by technological limitations,” says Guffogg.
This is because existing satellite technology used to spot plastic floating in water can’t as easily distinguish between plastic and sand on beaches.
The new Beached Plastic Debris Index (BPDI) provides an answer.
It’s what’s known as spectral index – a mathematical formula which sorts patterns of reflected light collected by satellites to detect the ones of interest.
The BPDI maps the characteristics of shortwave infrared light reflected off plastic debris, which is unique compared to sand and other organic material washed up on a coastline. It uses data from the Sun-synchronous WorldView-3 satellite, which orbits the Earth in line with the Sun at an altitude of 617 km.
The researchers tested the BPDI’s performance by placing 14 plastic targets on a beach in southern Gippsland, Victoria. Each target was made of a different type of plastic and, at 2m2 in size, were smaller than the satellite’s pixel size (3m2).
They found the BPDI successfully distinguished the plastic targets from sand, water, and vegetation while outperforming 3 other existing indices.
“This is incredibly exciting, as up to now we have not had a tool for detecting plastics in coastal environments from space,” says co-author Dr Mariela Soto-Berelov of RMIT.
“The beauty of satellite imagery is that it can capture large and remote areas at regular intervals.
“Detection is a key step needed for understanding where plastic debris is accumulating and planning clean-up operations, which aligns with several Sustainable Development Goals, such as Protecting Seas and Oceans.”
She says the next step is to test the BPDI in real life scenarios.
“We’re looking to partner with organisations on the next step of this research; this is a chance to help us protect delicate beaches from plastic waste,” says Soto-Berelov.
