The ocean's health is threatened in numerous ways by the presence of plastic, writes BARBARA THOMSON
I recently 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 the plight of marine litter in our precious oceans.
This is why a day such as, World Oceans Day (WOD) is incredibly important, as it raises awareness about the plight of our oceans.
WOD is celebrated annually on June 8. The proposal for this important day, was first tabled at the 1992 Earth Summit held in Rio de Janeiro, Brazil, but it was only officially recognised in 2008 by the UN, where it is currently observed by all member states, including South Africa.
The day is aimed at appreciating, protecting, restoring and honouring ecosystem services and resources provided by our oceans.
In the light of the fact that often members of the public are not aware that coastal litter is actually generated further inland, South Africa has adopted the extended theme: “From mountains, rivers, to the ocean floor – a nation at work towards healthy oceans and a healthy planet.”
Indubitably our oceans contribute to a healthy planet and a healthy society.
They provide us with water as a basic element of life, protein through its living resources, is a driving force of our climate by providing rain and buffers us from the impacts 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. Furthermore 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. The day raises awareness of the vital role of oceans to society, and hence, its environmental management is necessary.
The WOD is significantly important to highlight the need for waste management, recycling, ocean and coastal conservation.
The presence of plastics in the ocean threatens ocean health in several ways.
Macro-plastics cause injury and death to marine animals and seabirds. As plastics break down into smaller fragments over time, it can be ingested by shellfish and other wildlife or accumulate in marine sediment.
It has the potential to spread throughout the food web as animals consume each other. Some research has shown the presence of plastics can affect both the number and type of marine organisms that inhabit a particular area.
Plastics are capable of absorbing and accumulating toxic compounds present in the water, which can be transferred to living organisms once ingested. At sea, sources include lost and discarded nets and lines from fishing vessels as well as plastic floats and traps that are lost at sea.
Land-based sources emanate from ordinary litter and materials disposed in open landfills that are blown or washed away entering the ocean through waterways, wastewater outflows and the wind. Over time plastic debris is broken down into smaller fragments and may accumulate in the marine sediment.
Floating lightweight plastic is carried by ocean currents for hundreds of kilometres and is mistaken as prey by other species including turtles, seabirds and other marine predators.
Marine species are vulnerable to ocean pollution in all stages of life from eggs to hatchlings; juveniles to adults. For example, sea turtles may mistakenly see floating plastic as jelly fish, or get entangled in discarded fishing nets and lines.
Laboratory experiments demonstrated that green and loggerhead turtles are the most common turtles affected by ingestion of macro-plastic debris mainly mixed with food items or single 1-10cm-square plastic sheets. But even in small quantities, plastic can kill sea turtles with a blockage of the oesophagus or perforation of the bowel.
Plastic ingestion can have all sorts of consequences, including decreases in growth rate and longer developmental stages. Lower reproductive output and lower survivorship are experienced and when energy reserves are depleted, the animals become more vulnerable to predators.
Pollutants, including toxic plastic, persistent organic pollutants, heavy metals, petroleum products, and so on, may cause immediate harm to marine species through direct contact or build up in tissues over time which can lead to immune-suppression resulting in diseases and/or death.
It also poses a serious threat to marine habitat over a larger scale and may also affect human health when contaminated seafood is consumed.
According to research, South Africa is ranked 11th in the world with 56% of mismanaged waste.
The quantity of mismanaged plastic waste equates to 0.63 million metric tons per year contributing about 2% of mismanaged plastic waste globally. It has been estimated the amount of plastic litter present in the world’s oceans amounts to 130 million tons.
An average of about 8 million tons of plastic ends up in the oceans per year. At that rate, there will likely be more than 250 million tons of plastic in the oceans within the next 10 years.
It is vital that celebrations such as World Oceans Day be utilised to raise more awareness about the problem of plastic litter and to encourage the public to make a practical contribution by participating in a clean-up campaign.
* Thomson is the Deputy Minister of the Department of Environmental Affairs.