Plastic is spreading through the oceans, endangering 690 marine species, some of which are at risk of extinction. Microplastics and microfibres are the worst threats.
Every year an estimated eight million tonnes of plastic, worth 19.5 billion euros, float through the oceans. Eighty per cent of ocean waste is of anthropogenic origin and comes from land, while the remaining 20 per cent arrives from ships – cruise ships, cargo vessels or offshore platforms, such as oil rigs. If lifestyles do not change, according to the Stemming the Tide report produced by Ocean Conservancy, by 2025 there could be one tonne of plastic for every three tonnes of fish in the ocean.
A "sea" (of plastic) within the sea that undermines the very survival of the marine ecosystem. Waste, debris, fishing gear, plastic bags and even straws represent a deadly threat to marine life.
Fishing lines and nets are dangerous not only when they are being used for fishing, but continue to threaten birds, turtles and cetaceans even after they have served their primary purpose, wrapping around animals in a deadly embrace. Plastic bags are easily mistaken for jellyfish and swallowed as food, while plastic straws can become lodged in a nostril, an eye or even the throat of a sea turtle or any other marine animal. According to a recent study, 690 species are threatened by waste present in the sea: 17 per cent of these are listed on the red lists of animals at risk of extinction, 92 per cent are endangered by plastic, and 10 per cent have ingested microplastics.
Forecasts for the future are far from rosy: according to a report produced by the Ellen MacArthur Foundation together with the McKinsey Center for Business and Environment, by 2050 there will be more plastic than fish in the oceans. According to the analysis, the ratio between the tonnes of plastic present in the oceans and those of fish, which currently stands at one to five, will become one to three as early as 2025. Then, a quarter of a century later, the quantity of fish in the sea will be lower than that of plastic waste.
But the problem is far more pervasive and deep-rooted than one might imagine. When we talk about plastic, we immediately think of floating islands of rubbish; in reality the issue is far more complex, and what impacts marine animals above all are microplastics — plastic fragments smaller than 5 millimetres, which can be produced by industry (for example the microbeads used in cosmetics or personal hygiene products, toothpastes being particularly rich in them) or can derive from the degradation at sea, through the action of wind, wave motion or ultraviolet light, of larger plastic objects.
Microplastics affect all marine animals, from microscopic krill (the collective term for the small crustaceans that represent the primary food source for many marine animals) to the great predators at the apex of the food chain, reaching us in turn through the food we eat.
According to Greenpeace data, between 5,000 and 50,000 billion microplastics are found in the seas across the entire planet, and Unep data show that 250 billion fragments are swimming in the Mediterranean, amounting to around 677 tonnes per year, although almost 90 per cent are fragments of larger objects, such as bottles or bottle caps.
In 1960, plastic had been found in the stomachs of fewer than 5 per cent of seabirds; by 2010 that figure had already risen to 80 per cent. Based on current trends, it is estimated that plastic ingestion will affect as many as 99 per cent of all seabird species by 2050. These are the findings contained in a study published in the Proceedings of the National Academy of Sciences and produced by researchers at Imperial College London and the Commonwealth Scientific and Industrial Research Organisation (Csiro) in Australia. The researchers note that today 90 per cent of seabirds, including albatrosses, shearwaters and penguins, have ingested plastic material of various kinds, from bags and bottle caps to fibres from synthetic clothing.
Birds mistake brightly coloured objects for food or ingest them accidentally, and the impact on their health can be devastating: ranging from various forms of poisoning to death. Turtles and cetaceans eat plastic bags thinking they are jellyfish; sharks mistake pieces of plastic for fish. Despite these observations, scientists cannot explain why so many animals, from plankton to whales, make this mistake, which can often prove fatal.
One explanation may come from a new study published in the journal Science Advances, which suggests the answer could be that plastic smells like food. Krill feed on algae. When algae die and decompose, they emit a sulphurous smell generated by dimethyl sulphide (DMS). Seabirds have learned that this smell indicates the presence of krill.
According to the research, plastic waste is an ideal substrate for algal growth — that slightly slimy, greenish layer that often coats pieces of plastic found at sea. When the algae die and decompose they emit the smell of dimethyl sulphide, and seabirds, which use their sense of smell to find food, are deceived by what are described as "olfactory traps" that lead them to mistake plastic for krill.
Plastic can have various effects on marine animals, from suffocation to poisoning. A National Geographic video captures very effectively the experience of an animal when it encounters a piece of plastic.
Washing clothes is a threat to our seas. We have always been told that detergents pollute water, which is why they should be used sparingly and, where possible, be biodegradable and free of optical brighteners. But we have never been told that washing clothes is a source of pollution due to all the plastic microfibres that polyester garments release with every wash. Today it is estimated that there are 1.4 million trillion microfibres in marine waters.
Today 60 per cent of clothing produced is made from synthetic material, and according to a recent study published in the journal Environmental Science and Technology, with every wash large quantities of synthetic fibres such as acrylic, polyethylene, polypropylene, polyamide and polyester detach from clothes and make their way into the sea, and no wastewater treatment can prevent this.
