Ocean plastic in numbers: what really ends up in the sea

The numbers you come across vary a lot. That is rarely down to bad research. It depends on what is counted: the whole environment, all waters or only the sea, and for which year.

• The whole environment: according to the OECD, 22 million tonnes of plastic leaked into the environment in 2019. A study in Nature puts the figure for 2020 at around 52 million tonnes of plastic waste released into the environment without any control. 57 percent of it is burned in the open, and 43 percent stays on land as litter, from where it can reach waterways.
• All waters: the UN Environment Programme (UNEP) estimates that 19 to 23 million tonnes of plastic waste get into lakes, rivers and seas every year. The OECD puts the figure for 2019 at 6.1 million tonnes. The two figures come from different models and reference years.
• The sea only: according to the OECD, 1.7 million tonnes reached the sea in 2019.

Plastic doesn't disappear, it only breaks into smaller and smaller pieces. That is why the amount in the sea grows year after year. The OECD puts it at around 30 million tonnes, UNEP gives a range of 75 to 199 million tonnes. That the estimates are so far apart mostly shows how hard the sea is to measure.

And it is getting worse: without meaningful action, UNEP projects that the plastic entering water will nearly triple by 2040.

Ghost nets are fishing nets that were lost or left behind in the sea. Nobody hauls them in any more, but they keep catching: fish and other sea creatures get tangled in them. On the seabed, according to WWF, nets like these take 400 to 600 years to break down.

A study in Science Advances estimates that almost 2 percent of all fishing gear is lost in the sea every year. Nobody knows exactly how large its share of all ocean plastic is. For some areas there are measurements, though: at least 79,000 tonnes of plastic float in the Great Pacific Garbage Patch, and at least 46 percent of that mass is fishing nets. A 2022 estimate even suggests that 75 to 86 percent of the floating plastic mass there (pieces over 5 cm) could come from fishing.

WWF Germany has been searching for and recovering ghost nets in the Baltic Sea since 2013. Since it started using sonar in 2018, it has recovered 33 tonnes of ghost nets, according to WWF. On a single recovery trip in 2020 it brought up more than nine tonnes in three days, according to WWF its largest haul on one trip so far.

Since February 2025 the GhostNetZero.AI platform has been publicly accessible. Individuals and organisations can upload sonar data from the seabed, and an AI flags possible ghost nets with 94 percent accuracy, according to WWF. Specialists review the hits, and divers check confirmed spots through the free GhostNetZero app. The nets recovered from the Baltic can't be recycled, by the way: according to WWF they are too heavily contaminated with sand and lead.

Every focus hour funds the recovery of about 50 g of ocean plastic, together with WWF and GhostNetZero. A kilo takes 20 hours, and 100 hours in a month reach the cap of 5 kg. How it works in detail is explained on the ocean impact page.

To be honest: next to 1.7 million tonnes a year, a few kilos are tiny. But every net that is recovered stops catching. And your child sees in the app what their focused time has achieved. That is a good starting point for a conversation, for example with the numbers in this article.