RMIT scientists say plastic rubbish on beaches can now be seen from space

Australian RMIT University scientists have developed a new method for spotting plastic rubbish on beaches, successfully field testing it on a remote stretch of coastline.

The satellite imagery tool picks up differences in how sand, water and plastics reflect light, allowing plastics to be spotted on shorelines from more than 600 kilometres above.

Satellite technology is already used to track plastic floating around the oceans – from relatively small drifts containing thousands of plastic bottles, bags and fishing nets, up to gigantic floating trash islands like the Great Pacific Garbage Patch, which is three times the size of France.

However, the satellite technology used to spot plastic floating in water doesn’t work as well for spotting plastic lying on beaches, where it can easily blend in with the sand.

This latest advance means rubbish can be more easily accessed and removed by clean-up operations.

Dr Jenna Guffogg, study lead author, said plastic on beaches can have severe impacts on wildlife and their habitats, just as it does in open waters.

“Plastics can be mistaken for food, larger animals become entangled and smaller ones, like hermit crabs, become trapped inside items such as plastic containers,” she said.

“Remote island beaches have some of the highest recorded densities of plastics in the world, and we’re also seeing increasing volumes of plastics and derelict fishing gear on the remote shorelines of northern Australia.”

Guffogg said if these plastics are not removed, they inevitably 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,” she said.

The team’s Beached Plastic Debris Index (BPDI) is what’s known as a spectral index.

The BPDP is a mathematical formula that sorts patterns of reflected light collected by satellites as they pass over an area, to reveal what you’re most interested in seeing from the image.

The remote sensing team at RMIT have developed similar tools for monitoring forests and mapping bushfires from space.

The BPDI is tailored to mapping plastic debris in beach environments using high-definition data from the WorldView-3 satellite, which orbits the earth in line with the sun at an altitude of 617 kilometres.

Dr Mariela Soto-Berelov, study co-author, said the enhanced separability of the BPDI against water, in addition to sand, suggests its utility is superior in environments where water pixels and plastic-contaminated pixels are likely to coexist.

“This is incredibly exciting, as up to now we have not had a tool for detecting plastics in coastal environments from space,” she said.

“The beauty of satellite imagery is that it can capture large and remote areas at regular intervals.

“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.”

For more information, www.rmit.com.au