A study conducted at Utrecht University shows that there is significantly less plastic waste in the global ocean than scientists previously thought. This new insight came from calculations with a computer model that includes a record number of measurements and observations of plastic in the ocean, says the university in a press release. The study also reveals that a large proportion of the plastic in the ocean consists of large pieces that are easier to clean up.
To date, the total amount of plastic in the ocean has been estimated at more than 25 million tons, of which a quarter of a million tons float on the ocean surface. However, this new study shows that the amount of plastic on the ocean surface is much higher, at about 2 million tons, but only one million tons is present in the deeper ocean (this excludes the amount of plastic on the bottom of the ocean). This means the total amount of plastic in the ocean is much lower but the proportion floating on the surface is relatively large.
- Utrecht University study finds less plastic waste in oceans than thought – around 2 million tons, with a larger portion on the surface.
- New plastic entering oceans annually is only half a million tons, highlighting the early stage of plastic pollution research.
- Large floating plastic pieces on the surface are easier to clean than microplastics; plastic remains in oceans for decades, requiring sustained efforts for effective reduction.
Infancy
Very less new plastic ends up in the ocean per year than previously believed: half a million tons instead of 4 to 12 million. The numbers show enormous differences. According to Mikael Kaandorp, lead author of the study, this shows that research on plastic in the ocean is in its infancy. “We are really still looking for order of magnitude,” he says.
Decades in the ocean
While most plastic particles in the ocean are very small, the total mass of those microplastics is relatively small. A surprising finding given the expectations, says Erik van Sebille, Kaandorp’s PhD supervisor. And good news, is “Large, floating pieces on the surface are easier to clean up than microplastics.” Incidentally, the study also shows that about half of those large pieces come from fishing boats.
Another important conclusion drawn by the researchers is that plastic remains in the ocean much longer than thought, roughly decades. Also, less plastic ends up in the ocean per year but the amount floating on the surface is much larger. And that, according to Kaandorp, is bad news: “It means that it will take much longer until the effects of measures to combat plastic waste will be visible. It will be even more difficult to get back to the situation as it once was. Also, if we don’t take action now, the effects will be felt for much longer.”
Complex computer model
The new predictions about the amounts of plastic in the ocean were made with a computer model. Kaandorp fed the model with measurements and observations of the amounts of plastic in the ocean. Then the model derived the total amount of plastic from that. It used a diverse array of variables, including the rate at which plastic washes ashore, breaks up into smaller pieces, and becomes covered in algae, making it heavier and sinking to the bottom.
Record amount of data
Previous estimates of quantities of plastic have also been made with computer models. This model stands out because of the record number of measurements and observations included. “Therefore, this model is more accurate,” Kaandorp says. “Until now, scientists were mainly looking at measurements of amounts of plastic in the upper layer of the water surface. We added counts of beach cleanups in various places around the world, and observations of large floating plastic objects on the water, among other things. Those pieces are relatively scarce, but because they are heavy, they make up a large portion of the total amount of plastic in the ocean.”
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