Picture: REUTERS
Picture: REUTERS

RECENTLY I came across a report from the Ellen MacArthur Foundation, which said plastic rubbish could outweigh fish in the oceans by the year 2050. This alarming report highlights that as South Africans we need to do much more to combat marine litter in our precious oceans.

On World Ocean Day on June 8, and in light of the fact that members of the public often do not know coastal litter is actually generated further inland, SA has adopted the extended theme From mountains, rivers, to the ocean floor — a nation at work towards healthy oceans and a healthy planet.

Our oceans indubitably contribute to a healthy planet and a healthy society. They provide us with water and protein, are a driving force of our climate by providing rain, and buffer us from the effects of global warming by absorbing carbon and heat.

Our oceans serve as the world’s largest source of protein, with more than 3-billion people depending on the oceans as their primary source of food. Oceans directly support a range of economic activities such as oil and gas exploration, fishing and aquaculture. New benefits such as bioprospecting for medicinal applications are also emerging. World Ocean Day highlights the need for waste management, recycling and ocean and coastal conservation.

The presence of plastic threatens ocean health in several ways. Macro-plastics cause injury and death to marine animals and seabirds. As plastic breaks down into smaller fragments, it can be ingested by shellfish and other wildlife or accumulate in marine sediment. It can spread throughout the food web as animals consume one other.

Research has shown that the presence of plastics can affect both the number and type of marine organisms that inhabit a particular area. Plastics can absorb and accumulate toxic compounds present in water, which can be transferred to living organisms once ingested.

At sea, sources of plastic include lost and discarded nets and lines from fishing vessels as well as plastic floats and traps.

Land-based sources emanate from ordinary litter and materials thrown into open landfills that are blown or washed away, which enter oceans via waterways, wastewater outflows and the wind. Floating lightweight plastic is carried by ocean currents for hundreds of kilometres and is mistaken as prey by marine predators including turtles and birds.

Marine species are vulnerable to ocean pollution in all stages of life, from eggs to hatchlings, juveniles to adults. Turtles may mistake floating plastic for jelly fish, or become entangled in discarded fishing nets and lines. Green and loggerhead turtles are the most common turtles affected by ingestion of macro-plastic debris mainly mixed with food items, or single plastic sheets of 1cm² one to 10cm² in size.

Even in small quantities, plastic can kill sea turtles by blocking the oesophagus or perforating the bowel. Other consequences of plastic ingestion include slower growth, longer developmental stages, lower reproductive output and survivorship, and increased vulnerability to predators as energy reserves are depleted.

Pollutants including persistent organic pollutants, heavy metals and petroleum products may cause immediate harm to marine species through direct contact, or build-up in tissues over time, causing immune suppression and resulting in diseases and/or death.

Plastic poses a serious threat to marine habitat and may affect human health when contaminated seafood is consumed.

SA is ranked 11th in the world for waste mismanagement, with 56% of its waste deemed to be mismanaged. The quantity of mismanaged plastic waste equates to 630,000 tonnes a year, contributing about 2% of mismanaged plastic waste globally. It has been estimated that the total amount of plastic litter present in the world’s oceans amounts to 130-million tonnes. An average of about 8-million tonnes of plastic ends up in the oceans each year. At that rate, there is likely to be more than 250-million tonnes of plastic in the oceans within the next 10 years.

It is therefore fitting and vital that celebrations such as World Oceans Day be used to raise more awareness about the problem of plastic litter, and to encourage the public to make a practical contribution by participating in clean-up campaigns.

• Thomson is the deputy minister of environmental affairs