While satellite technology has long been used to monitor floating plastic in the world's oceans - tracking both smaller plastic clusters and expansive trash islands like the Great Pacific Garbage Patch - detecting plastic on beaches has proven challenging due to the way it blends with the sand. This new method addresses that limitation, marking a significant step forward for coastal clean-up operations and plastic waste management.
The study, published in 'Marine Pollution Bulletin', indicates that this innovation allows for more efficient identification of beach plastics, which can then be removed before breaking down into more hazardous micro and nano-plastics.
The Scope of Plastic Pollution
More than 10 million tons of plastic end up in the ocean each year, with estimates suggesting that this figure could reach 60 million tons annually by 2030. Study lead author Dr. Jenna Guffogg highlighted the severe effects of plastic pollution on wildlife along coastlines, similar to the impact seen 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," Guffogg explained. "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."
If left unchecked, she noted, these plastics inevitably fragment into smaller particles, adding to the mounting environmental concern.
Advances in Detection
RMIT's Beached Plastic Debris Index (BPDI), a spectral index, utilizes a mathematical formula that interprets the reflected light patterns captured by satellites as they scan beach areas. RMIT's remote sensing team previously created similar indices for forest monitoring and bushfire mapping from space, and now they've applied these principles to beach environments using high-definition data from the WorldView-3 satellite, which orbits at 617 kilometers.
For testing, 14 plastic targets, each about two square meters in size and made from different types of plastic, were placed on a beach in Victoria. Despite each plastic target being smaller than the satellite's pixel resolution of three square meters, the BPDI demonstrated accuracy superior to three existing indices, two of which are designed for terrestrial plastic detection and one for aquatic environments. Other indices struggled to distinguish plastic from beach shadows or water, whereas the BPDI achieved clear separation.
Study co-author Dr. Mariela Soto-Berelov noted, "This is incredibly exciting, as up to now we have not had a tool for detecting plastics in coastal environments from space." She emphasized that satellite imagery's vast reach allows for regular monitoring of extensive and remote areas, which is essential for identifying plastic accumulation hotspots and facilitating clean-up efforts. These capabilities align with key Sustainable Development Goals, such as Protecting Seas and Oceans.
Next Steps
The researchers are seeking partnerships to advance the BPDI for practical applications. "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," Soto-Berelov added.
Guffogg, who completed the study as part of her joint PhD research at RMIT University and the University of Twente, now works in geospatial mapping. Her research received support from an Australian Government Research Training Program (RTP) scholarship, and the WorldView-3 satellite imagery was provided by US-based DigitalGlobe.
Research Report:Beached Plastic Debris Index; A modern index for detecting plastics on beaches
Related Links
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Our Polluted World and Cleaning It Up
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