Though hyper-exaggerated pictures of garbage patches and models extrapolated from a fishing line study in the 1980s get all of the media attention when it comes to pollution, it causes activist groups to raise money by focusing on the wrong thing. The most efficient way to clean up ocean plastics and avoid harming ecosystems is to stop litter on the coasts.
Plastic can persist for decades and fragments could be swallowed by animals and enter the food web, disrupting ecosystems, though it doesn't happen often. What does happen often is picture-taking of an unusually large collection of microscopic plastics known as the Great Pacific garbage patch. The patch is enclosed by ocean currents that concentrate the plastics into an area that some estimate could be twice the size of the United Kingdom. Why estimated, if it that large it can be seen from space, right? Welcome to environmentalism.
Though The Ocean Cleanup that plans to deploy plastic collectors to clean up the region is laudable, someone is doing something, targeting the patch is good publicity but not the most efficient way to clean up the oceans. Unfortunately, that uses estimates as well.
D.r Erik van Sebille and undergraduate physics student Peter Sherman from Imperial College London used a model of ocean plastic movements to determine the best places to deploy plastic collectors to remove the most amount of microplastics, and to prevent the most harm to wildlife and ecosystems. The estimate is published today in Environmental Research Letters.
They found that placing plastic collectors like those proposed by The Ocean Cleanup project around coasts was more beneficial than placing them all inside the patch. The project proposes a system of floating barriers and platforms to concentrate and collect plastics and remove them.
For a ten-year project between 2015 and 2025, the team found that placing collectors near coasts, particularly around China and the Indonesian islands, would remove 31 percent of microplastics. With all the collectors in the patch, only 17 percent would be removed.
"The Great Pacific garbage patch has a huge mass of microplastics, but the largest flow of plastics is actually off the coasts, where it enters the oceans," said Sherman.
"It makes sense to remove plastics where they first enter the ocean around dense coastal economic and population centers," added van Sebille. "It also means you can remove the plastics before they have had a chance to do any harm. Plastics in the patch have travelled a long way and potentially already done a lot of harm."
The pair's model also looked at areas where microplastics overlapped with phytoplankton - microscopic floating plants that form the basic food of many ocean ecosystems. Many microplastics enter the food web in these areas as microscopic animals accidentally eat them.
Running the same model for areas rich in phytoplankton came up with a similar result: the overlap was reduced by 46 percent by placing collectors near certain coasts, whereas the overlap was only reduced by 14 percent by placing the collectors in the patch.
"There is a lot of plastic in the patch, but it's a relative dead zone for life compared with the richness around the coasts," said Sherman. A recent analysis by Dr van Sebille and colleagues in Australia showed that more than 90 percent of seabirds have swallowed plastics, and these birds are also concentrated around coasts where their food is plentiful.