One of the main causes of the litter problem is the increased use of plastics. The global production of plastics doubles every ten years. Plastics discarded in nature are carried to the sea by rainwater and rivers, where they are transported further by winds and marine currents.
Although we have become accustomed to seeing plastic rubbish on the seashore, mankind did not recognise the sheer scale of the marine littering problem until the discovery of huge rafts of plastic rubbish in the central vortexes of the world’s oceans.
The global production of plastics doubles every decade. One third of the world's produced plastic ends up as packaging material. Much of it is single-use plastic. Marine currents transport the litter that ends up in the seas to the centre of ocean vortexes. Source: SYKE. Illustration: Kaskas Media Oy.
The situation in the Baltic Sea is not as bad as on the shores of oceans
Marine litter can be found everywhere, even in seas like the Arctic Ocean, which are far from human settlements. The problem is most acute in developing countries where Western consumer culture is taking over, but both environmental awareness and waste management lag behind.
In the Baltic Sea, the investigation of the scale of the marine littering problem has only just begun. Nevertheless, the situation is not assumed to be as bad as the densely populated coasts of the world oceans.
The littering of the Finnish coastline is monitored by regularly counting litter from certain shores. The same method has been proposed as an official indicator of marine litter levels. In Finland, the concentrations of microlitter in water are also measured.
Most of the rubbish is plastic
Although marine litter can derive from a variety of sources, it is difficult to trace them when the rubbish is already in the sea. Today, it is estimated that the Baltic Sea is most commonly littered through tourism and vacationing. However, a lot of other waste also comes from other activities. The size of marine litter ranges from large pieces of rubbish to tiny particles of microlitter.
Most of the rubbish in Finnish marine areas consist of different plastics. Plastics are transported into waterways, both from industry and from the everyday lives of citizens. Plastic litter can fall on the street, e.g. from an overfilled litterbin, and then be transported along with rain runoff into the drains and eventually, to the sea.
Some of the plastic litter entering the sea via rivers has been transported very long distances. Rivers carry plastics, especially in spring and autumn. Conversely, some plastics derive from the seashore, ports, and shipping. Fishing gear, i.e. traps and nets, which have been abandoned in the sea, are also a significant source of plastic litter.
Around 300 million plastic bags are used annually in Finland. Even the plastic bag that falls beside the rubbish bin often ends up in the sea. The bag is caught by the wind blowing along the street and it continues the rest of the way to the sea via a ditch or stormwater drain. Likewise, litter thrown in the toilet can also end up in the sea because wastewater treatment plants do not remove all of the microlitter. Source: SYKE. Illustration: Kaskas Media Oy.
Plastic decomposes slowly in nature
Although ultraviolet radiation from the sun makes plastic brittle it does not properly break it down. In nature, it can take an extremely long time before the plastic really decomposes. Although both mechanical abrasion and high temperatures accelerate the decomposition process, it can still take tens or even hundreds of years.
Thus, winds and sea currents have plenty of time to transport plastic litter from one place to another. Over time, plastic breaks down into microplastics in the sea, but they are at least as damaging to marine nature as large plastic debris.