What if the issue of plastic waste mysteriously disappearing in the oceans had been resolved? What if the most likely hypothesis was before our eyes?
What happens to the millions of tons of plastic waste that end up in the oceans every year, but yet disappear?
99% of plastics disappear in the ocean
Have you ever heard of the mystery of missing plastic? Every year, four to twelve million tonnes of plastics are added to ocean pollution. Yet, paradoxically, scientists have found that only 250,000 tonnes are found on the surface. But then, where did the rest of this plastic go?
As a result, 99% of all plastic waste dumped into the oceans disappears. Of course, because of their density, even when attacked by the sun, bacteria and erosion, some flow to the depths. But Alethea Mountford, a researcher at Newcastle University, has succeeded in developing the beginnings of a computer model of ocean currents on plastics of three different densities.
Plastic returns to earth
Thus, the researchers were able to locate the places where the fragments gather after they have sunk. According to this model, they are found at different depths in the Mediterranean, in the Indian Ocean, and in the waters of Southeast Asia.
As recent dives to the bottom of the oceans have shown, much of it eventually settles on the seabed, up to miles deep where the material gradually degrades.
However, according to the work of oceanographer Éric van Sebille of the Dutch University of Utrecht, more than creating a real continent, sort of floating plastic dumps of all kinds, most of this waste actually ends up returning to the shores.
This intuition is still scientifically validated, even if it seems logical that plastic from rivers stays close to the coast and that an important part ends up on the shores.
Mostly stranded in the coastal zone
Despite the gigantic plastic continents floating on the surface of the sea, most of this material released into the ocean is never found. A mystery that scientists have been studying on for years, and to which a new study provides an answer… very simple. According to a study by CISRO researchers, in fact, 90% of marine plastic debris is washed up in the coastal zone, between 0 and 8 km from the ocean. If it is not directly visible on the beaches, the plastic released into the waves is, therefore “invisible” but not far from the coast.
To calculate this, the researchers analyzed coastal debris all around Australia every 100 km, representing 188 sites around the island. Once modeled on the factors affecting the distribution of this waste, they found that plastic accounts for just over half of waste (56%), followed by glass (17%), foam (10%), rubber (5%), metal and paper (3%).
In addition, there is five times more waste in the area furthest from the shore, where vegetation begins, than in the first few meters of beaches and shorelines, with many plastic wastes hanging in the branches before they even reach the ocean.
Should we focus on cleaning up coastal areas to prevent pollution from spreading offshore?