Human rubbish is smothering the planet’s oceans

A plastic bag on the seabed at  Calypso Deep, the deepest place in the Mediterranean at 5109 metres. Image: By Caladan Oceanic

In a throwaway world garbage may be unseen, but not gone. Human rubbish is everywhere, from ocean abyss to coastal mud.

LONDON, 29 January, 2021 − In the next 30 years, an estimated three billion metric tonnes of human rubbish − everything from abandoned trawl nets to plastic bottles, from broken teacups to tins of toxin − could find its way into the sea, to defile the ocean floor.

One recent survey in the Strait of Messina, the seaway that separates Italy and Sicily, measured this detritus at concentrations of between 121,000 and 1.3 million items per square kilometre trapped in submarine canyons.

In seabed fissures off Portugal, bits of human litter large enough to identify have been counted at rates of 11,000 per sq km. Off the Ryukyu Islands far from mainland Japan, divers and remotely operated vehicles have made estimates of up to 71,000 items per sq km.

There is more and worse lying on other parts of the seabed. An estimated one million tonnes of chemical weaponry could be scattered about the planet’s oceans. The North Sea floor could be host to 1.3 million tonnes of conventional and chemical weapons; the Baltic enfolds and flows over 385,00 tonnes of dropped bombs, grenades, torpedoes, landmines and other weaponry.

“As humans, we have little or no care at all to prevent litter from accumulating everywhere”

And, says a new study in the journal Environmental Research Letters, this conversion of sea floor to careless landfill site creates problems for at least 693 marine species that so far have been observed to “interact” with marine debris: eat it, get caught in it, grow on it. Of these species, around one in six are in some degree endangered.

This list of sea creatures includes 93 kinds of invertebrate, 89 fish, 83 birds, 38 mammals and all species of sea turtle. So many fish now become ensnared in abandoned and derelict fishing gear that they are known as “ghost catches.”

Across the Asia-Pacific region, an estimated 11.1 billion bits of plastic bigger than 25mm could be entangled in the coral reefs. This problem of marine pollution goes far beyond the concern over plastic pollution of the planet’s seas and shores, from pole to pole, and is now found even in marine tissues.

Much of the previous concern has been about the presence of microfibres and small particles of polymer material now found everywhere. But the new study by European scientists tries to address the more obvious problem of these larger items − generally larger than 25mms − of all kinds of detritus, including plastic denser than water and ultimately destined to reach the seabed.

Poor management

The researchers want to try to find standard ways to measure the levels of waste, map its concentrations accurately, identify all the sources of refuse and classify the most problematic kinds: the toxic waste, the heavy metals and radioactive substances, the pharmaceuticals. They also urge international co-operation, and policies designed to discourage marine discharges and to clear up stretches of the sea floor.

“Marine litter has reached the most remote places in the ocean, even the least − or never − frequented by our species and not yet mapped by science,” said Miquel Canals of the University of Barcelona, who led the study.

“In order to correct something bad, we must attack its cause. And the cause of the accumulation of waste on the coasts, seas and oceans , and all over the planet, is the excess waste generation and spillage in the environment, and poor or insufficient management practices.

“As humans, we have little or no care at all to prevent litter from accumulating everywhere.” − Climate News Network