Satellite Imagery Helps Detect Ocean Plastic Pollution
By Elizabeth Claire Alberts
In 2018, Lauren Biermann was scouring a satellite image of the ocean off the coast of the Isle of May, Scotland, searching for signs of floating seaweed for a project at her university. Her eyes were drawn to lines of white dots gently curving along an ocean front.
"It was weird because I was seeing floating things that didn't look like plants, and I didn't know what they could be," Biermann, an Earth observation scientist at Plymouth Marine Laboratory in the U.K., told Mongabay. She said she considered the fact that it could be plastic, but found it hard to believe that Scotland had patches of plastic off its coast. "I spent the first three months trying to prove that it wasn't plastic, so I went and made a library of all of the things floating, like foam and driftwood."
During her investigation, Biermann came across a project conducted by the University of the Aegean in Greece, in which a team of academic staff and students used drone and satellite image technology to identify "plastic targets," such as water bottles, plastic bags and fishing nets, on the sea surface. This data helped Biermann connect the dots in her own research.
"I went, yes, okay, this is plastic," Biermann said. "It was the first time I had … data to validate what I had seen in Scotland, and that's how I could build a spectral signature of plastic, and then go and apply it to other places."
More than 8.3 billion tons of plastic waste enter the oceans each year, equivalent to a garbage truck dumping its contents into the sea every minute of the day, according to a report by the World Economic Forum. Anything more than 5 millimeters in size, about a fifth of an inch, is generally considered to be "macroplastic," while anything below that size is "microplastic."
Biermann and a team of colleagues embarked on their own study of detecting ocean plastic through satellite imagery, and recently published their findings in Scientific Reports. First, they obtained high-resolution optical data from the European Space Agency (ESA), which is gathered by the Sentinel-2 Earth observation satellite. Second, they used the plastic target data from the University of the Aegean to help differentiate plastic debris from natural objects like driftwood and seaweed.
Then the researchers employed an algorithm to develop a "floating debris index" (FDI) that would identify macroplastics, like plastic water bottles and plastic bags, bobbing on the surface of the sea.
"I will read an article or a social media post about marine plastic pollution, and then go and look at that area, using Sentinel-2, and process the data using the floating debris index … and then extract those values and feed it into the machine learning algorithm," Biermann said.
Biermann and her colleagues have tested these methods on satellite imagery of coastal waters off Accra, Ghana; the San Juan Islands, U.S.; Da Nang, Vietnam; and east Scotland, reporting an 86% accuracy rate.
However, the process of identifying plastic isn't always straightforward. Cloud cover and rough seas can compromise the data, and macroplastics won't stay in one place for a long time, particularly in coastal zones, Biermann said. "Things change really quickly, so a Sentinel-2 image that I look at today would have been taken two days ago, and by then anything that I see is gone," she said.
While plastic tends to get pushed around in the ocean, winds and ocean currents will propel it into clusters that stay in one place. Biermann says she hopes that optical satellite data can help identify these aggregates, and that people and organizations can use this information to work on solutions.
"There will be cleanup operations like the Ocean Voyages Institute, which we'd like to work with. They would then go to where we spotted things, and they would be able to remove tons of plastic at a time," Biermann said. "This really is the first technical exercise, but we would then like to apply the method, far more broadly … to rivers and open waters."
Biermann makes an important clarification: this satellite data shouldn't be seen as a solution to the plastic pollution issue.
"On its own, it can't do anything to curb the plastic pollution problem," Biermann said. "The way to curb plastic pollution problem is to address the source. We know that the majority of plastics come from land, so it's not just addressing the source in terms of the industry, but also in terms of waste management practices on land."
She says she also hopes this data will help build awareness of the global plastic pollution issue, and inspire action on the issue.
"What I don't want to see is my work being used to greenwash the problem — now we can see it from space, so we know where to go and fetch it," she said. "That's not the case at all. And I think if anything, it's just to say there that there's enough of it now that it can be seen from space, [and we should] take that message to heart. The individual is not the problem here, and our individual behavior is not generating plastic on such a scale that it can be seen from space. Really, it is an industry problem."
Reposted with permission from Mongabay.
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EcoWatch Daily Newsletter
By Naomi Larsson
For centuries, the delicate silver dove has been a symbol of love and fidelity.
Biodiversity and Habitat Loss<p>Their near extinction is a symbol of the <a href="https://www.dw.com/en/global-biodiversity-outlook-targets-extinction-summit-new-york-pledge/a-54932895" target="_blank">biodiversity crisis</a> in the UK, largely driven by habitat destruction. Britain is now one of the countries with the most <a href="https://www.wwf.org.uk/future-of-UK-nature#:~:text=The%20UK%20is%20one%20of,than%20half%20are%20in%20decline" target="_blank">depleted nature</a> in the world according to the World Wildlife Fund. Half its plant and animal species are in decline and more than <a href="https://www.rspb.org.uk/about-the-rspb/about-us/media-centre/press-releases/let-nature-sing-wales/#:~:text=a%20natural%20tragedy.-,Over%2040%20million%20birds%20have%20vanished%20from%20UK%20skies%20in,unaware%20of%20the%20impending%20danger" target="_blank">40 million birds</a> have vanished in just half a century.</p><p>"[Turtle doves] are the canary in the [coal] mine because there are all these other species before it and after it," said Tree. "It's an umbrella for all the other species that are heading that way."</p><p>Turtle doves migrate south through Europe to sub-Saharan Africa between July and September, ending up in dry woodland and farmland areas of countries like Mali and Senegal for winter. </p><p>Droughts in West Africa and the Sahel region are believed to have contributed to the fall in turtle dove species recorded in northern Europe, with low rainfall reducing supplies of the seeds and insects the birds rely on for energy for the long journey home.</p>
Conservation and Farming<p><a href="https://www.operationturtledove.org/" target="_blank" rel="noopener noreferrer">Operation Turtle Dove,</a> a partnership project of charities including the Essex Wildlife trust, works with landowners and farmers to actively build turtle dove habitat.</p><p>Outten works with <a href="https://www.ebws.org.uk/birdsites/blue-house-farm-ewt-north-fambridge" target="_blank">Blue House Farm</a>, a 660-acre nature reserve in the UK county of Essex, where they have replicated weedy fallow plots. </p><p>"We work on it every year to make sure it's in the condition it needs to be with plants such as clovers and black medic," Outten said. "These plants are native to the landscape and produce the seed the birds feed on." </p><p>The birds eat a wide range of seeds from various plants that would have been abundant 50 or 100 years ago, added Guy Anderson, program manager for species recovery with The Royal Society for the Protection of Birds (RSPB). </p><p>"But it's simply true that with the gradual process of <a href="https://www.dw.com/en/farming-without-pesticides-how-can-we-make-agriculture-greener/a-52216796" target="_blank" rel="noopener noreferrer">intensifying our agricultural production</a>, the availability of those seeds has dropped and dropped," said Anderson.</p><p>Part of the project includes supplementary feeding — providing sources of food in the form of seed or grain. Under the Countryside Stewardship Scheme in England, farmers can receive financial support to create a turtle dove habitat. </p><p>Though they haven't recorded an increase in doves across the sites in the four years of working on the project, Outten said they are seeing improvements in how landowners and farmers manage habitat for the birds. </p>
A Turtle Dove Haven<p>The 3,500-acre Knepp Estate in West Sussex is another project taking a different approach and one of the few places where turtle dove numbers are increasing.</p><p>Isabella Tree and her husband Charlie Burrell converted their intensively farmed land into a rewilding project almost 20 years ago. They have let the land return to nature.</p><p>Just one year after they'd finished <a href="https://www.dw.com/en/uks-most-talented-architects-are-not-human/a-35952128" target="_blank">rewilding</a> the southern part of their property, they heard turtle doves for the first time. It's now a breeding hotspot for the birds with an estimated 19 pairs. Knepp is also home to <a href="https://www.rewildingbritain.org.uk/rewilding/rewilding-projects/knepp-estate" target="_blank" rel="noopener noreferrer">2% of the UK's population</a> of nightingales. </p><p>Tree is critical of supplementary feeding schemes that, in her view, are short term. She questions the chances of turtle doves getting to feed on scattered seeds before other mammals eat them first.</p>
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