Satellite imaging now reveals plastic waste on beaches
Take an afternoon stroll along any major beach, and you’re likely to stumble across some abandoned rubbish. Plastic scraps such as old water bottles, trashbags, straws and other plastic items litter beaches around the world. They eventually make their way to the ocean, where they will degrade for decades or centuries. International Coastal Cleanup and Ocean Conservancy estimate that volunteers from 97 different countries will have identified and removed 4,000 tons worth of trash from beaches around the world by 2021. Most of the time, it takes a naked eye to spot all the garbage. It also requires a lot of walking. Researchers from RMIT University, Australia have developed a new satellite-imaging technique that could change this. The team created a tool that highlights the unique spectral characteristics of plastics. Researchers were able to identify plastics on beaches, distinguishing them from sand and water. This is an exciting development, because until now, we did not have a way to detect plastics on coastal environments from space,” Mariela Soto Berelov, study co-author, said in a press release. Plastic waste is not just a problem for the ocean
Satellite images have been used by scientists to identify plastics in the ocean, and giant garbage patches such as the Great Pacific Garbage Patch, for many years. The process is relatively effective for identifying large pieces of plastic in water. However, it is less efficient at spotting the plastic on beaches. Plastic on beaches is often buried or blended in with the sand, making it difficult to spot. While plastics littering the ocean receive more attention than coastal trash, it can have serious negative impacts on local wildlife. “Plastics are often mistaken as food by larger animals, and smaller creatures, such as hermit crabs, can become trapped in plastic containers.
These harmful effects don’t just affect life on the beach. Plastics that are not removed can end up being sucked into oceans where they slowly degrade into micro and nanoplastics. These tiny plastics then make their way into the food chain and are consumed by fish. Researchers worry that this cycle could even lead to an increase in microplastics found in humans, which can cause endocrine disruptions and a worsened reproductive system. The full extent of microplastics’s effects on human health still isn’t fully known.
Finding plastic in sand sack
That’s where the new plastic detection system comes in. The RMIT developed a “spectral index”, which looks for patterns in the reflected light from plastics. Plastics have unique properties in the SWIR electromagnetic spectrum, which are not present in organic debris or sand. Beached Plastic Debris Index (BPDI), which they developed, is a kind of filter that can be used to apply images captured by satellites. In this instance, the images were taken by WorldView 3, a satellite that orbits at 617 kilometers above Earth’s surface. The Canon EOS 760D images of targets 1, 6, and 7 are shown in c), d), e). In f), you can see the images taken by a DJI Phantom Pro. They show more detail of the plastic targets. Credit: RMIT University
To try out their new tool, researchers collected plastic waste that they would expect to find on the beach. The majority of the objects collected were pieces of larger trash. Some of the objects had also faded colors from UV exposure. This is likely to happen with trash lying dormant at beaches. The final selection was 14 plastic targets, each measuring approximately two square meters. They were 3.7 meters apart on a Victoria beach, Australia. Once the plastics had been placed, the satellite flew high above and took a series photos. Researchers compared their index with three other induces that were already developed to detect plastics. Two of them were for plastics floating on the ocean and one was for plastics on the land. The BPDI index was more accurate than the other three indexes. The other indices struggled with identifying plastics, and in some cases would misidentify shadows. The BPDI index was not perfect. The study noted that it had difficulty identifying translucent polymers such as plastic bags and water bottles. In the future, researchers hope to take their findings beyond the limited testing environments to the real world. This could involve partnering with organizations that specialize in the removal of coastal plastic to use satellite imagery. The time is critical. “We are looking for organizations to partner with on the next stage of this research,” Soto Berelov said. This is an opportunity to protect fragile beaches from plastic waste.
