New research indicates that merchant shipping is likely responsible for a rapid increase in the amount of plastic bottles found in the world’s oceans and that Asian merchant ships are the big polluters.
Plastic bottles discarded into the ocean are now the fastest growing source of marine pollution, according to research carried out by a South African research team from the University of Cape Town. And merchant shipping, particularly from Asia, is to blame. Researchers now believe that, contrary to the commonly held belief, it is merchant shipping and not land-based sources that account for most marine plastic pollution.
Noting that it is “widely assumed” that 80% of marine plastics originate on land, the researchers say that “there is little robust evidence to support this estimate.” They further noted that several studies have reported the continuing accumulation of debris from “distant countries,” even after the dumping of plastics into the sea was banned by Annex V of the International Convention for the Prevention of Pollution from Ships (or, as it is commonly known, “Marpol”).
And so they set out to the aptly named Inaccessible Island in the South Atlantic to find out more.
Inaccessible Island — accessible plastics garbage dump
Plastic rubbish has been found at Inaccessible Island since 1984. South African researchers also visited in 2009 and in 2018. In 2009 they found 3,515 items of rubbish over a 1.1-kilometer distance on the west coast of Inaccessible Island. In 2018, they found 7,368 items weighing 5 metric tonnes (a metric tonne is equivalent to 2,204.6 U.S. pounds). Over the 72-day research trip, a further 239 bits of plastic rubbish washed up and 477 items were dug up.
Plastic drink bottles landing on the remote Inaccessible Island in the South Atlantic are showing a high accumulation rate, about 15% compared to 7% per year for all other types of plastic.
Bottles and other single-use containers (aerosols, food jars and so on) were the single most abundant type of plastic waste and they were typically made from polyethylene terephthalate (PET) or high-density polyethylene (HDPE).
Nearly two-thirds of bottles
Almost all identified plastic bottles were water or soft drink bottles. Water bottles comprised 61% of drink bottles overall. The other common types of bottles found were those used in domestic settings for holding cooking oil, other food products, detergents, soaps, shampoo, cleaning products and so on.
“The numbers of drink bottles at Inaccessible Island have increased at more than twice the rate of non-bottle debris during the last three decades. This largely reflects the 8.5% per year growth in the bottled water industry, which is projected to be worth US$280 billion by 2020,” researchers say.
Because plastic bottles are light, with a density similar to water, they can disperse a long way from the point where they were discarded. They tend to accumulate in areas with large circulating ocean currents (called ocean “gyres”). Islands near oceanic gyres therefore “suffer exceptionally high levels of plastic pollution, despite being located far from major source areas for plastic waste,” the researchers say.
So how old and were from?
The researchers sought to understand the origin of all the plastic bottles. Bottles often carry labels that display manufacturer brands, which makes them a “valuable tool to infer debris sources.”
In the 1980s, two-thirds of bottles found on Inaccessible Island originated in South America. By 2018, Asian bottles accounted for 75% of all bottles. Of note was that the volume of Asia-source bottles was higher among newly arrived bottles than among accumulated bottles.
The single biggest brand of plastic bottles found were from the Coca-Cola Company (Coke, Sprite, Fanta, Schweppes and others) of the U.S. Other major brands found include bottles from Tingyi/Master Kong (China), Nongfu Spring (China) and Hangzhou Wahaha Group (China).
Asia accounted for about 74.5% of all found bottles (China itself accounted for 50.6%) and South America for another 20.1% of all found bottles. The researchers noted that “half of all bottles came from China, a country from which no bottles had been recorded in previous visits in the 1980s and 2009.”
Plastic bottles are often date-stamped, or date-engraved, which helps researchers to work out how long the bottles have been at sea. The oldest bottle found was just under 50 years old — it had survived literally decades of being bashed about in the sea, hitting rocks and pebbles on the beach of Inaccessible Island, and years upon years of exposure to ultraviolet light from the sun.
About 478 of the found bottles were checked for age (about 17% of all bottles) and grouped into categories. The group with the biggest number of bottles in it was the one containing bottles that were one to two years in age. PET bottles were typically younger than bottles made from other plastics.
Data puzzle
A small proportion of Asian bottles were swept into the South Atlantic by the Agulhas Current and this will take three to five years, researchers say. However, seaborne plastic garbage from China, Taiwan, Japan and Korea is mostly swept by local currents into the North Pacific.
So why, then, was there such a massive rate of increase of young (up to two years old) north Asian-origin bottles into the South Atlantic when currents in north Asia would sweep the vast majority of them into the Pacific?
The answer, of course, is that the bottles had to be carried out from the origin region, Asia, by humans to a place where they could wash up on remote Inaccessible Island.
How were they carried into the South Atlantic?
Researchers noted that some bottles could be exported and sold outside of their regions but little Chinese water is exported to South America or Asia. “Virtually all bottle water and soft drinks for sale in these regions are manufactured locally,” the researchers say.
So, clearly, the plastic bottles were not washed off the land in either South America or South Africa.
Researchers also found that goose barnacles were attached much more frequently and in greater volume on younger Asian plastic bottles on Inaccessible Island than older Asian bottles on the same island. That “suggests that such items have not been at sea for very long, consistent with them being dumped.”
Fishing vessels or merchant ships?
There are only really two potential seaborne sources for the discarded Asian plastic that were found washed up on Inaccessible Island. They were either dumped from fishing vessels or they were dumped from merchant ships.
Researchers noted that, while plastics dumping from Asian fishing vessels has been frequently reported by observers, the level of activity by the Asian fishing fleet has been steady since the 1990s. And so that “does not explain the rapid increase in bottles during the last decade.” They also noted that most of the Asian fishing fleet in the South Atlantic is of Japanese or Taiwanese nationality and so that does not explain why there has been a large and fast recent rise of China-origin plastic bottles.
Researchers did note that merchant shipping (i.e., cargo-carrying shipping) traffic increased fourfold globally from 1992 to 2012 and that “there is an increasingly busy shipping lane from South America to Asia, principally China.” They further noted that more than 2,400 merchant ships passed by the Tristan da Cunha Island Group in 2016 at an average rate of 6.6 per day.
Researchers therefore concluded that “merchant shipping is probably responsible for much of the recent increase,” especially of Chinese bottles.
Independent researchers, different region, similar study, same results
Professor Peter Ryan, who headed the research, is a director at the FitzPatrick Institute of African Ornithology at the University of Cape Town in South Africa. In addition to his own team’s research, he sent an academic paper to FreightWaves showing a study from 2017-18 that was carried out in a small area of the Australian east coast.
The Australian researchers had very similar findings — lots of distinctively Asia-origin plastic bottles in good condition on Australian beaches but lacking colonizing marine organisms (which would be expected if the bottles had washed up in Australia from elsewhere).
The researchers in the Australian study also concluded that the large numbers of merchant ships passing the coast each day (up to 15 daily) were dumping their garbage. This inference was reinforced by the discovery of a large, partially burned bale of plastic waste that could only have been the result of incomplete combustion from a ship’s incinerator.
“Since then we have done more surveys in South Africa and Kenya and find most water bottles come from China, Singapore/Malaysia and UAE, again pointing the finger at merchant shipping as the major culprits,” Ryan told FreightWaves.
The South African researchers called for “urgent action … to reduce illegal dumping by all vessels, which is in contravention of MARPOL Annex V.”
Researchers visited Inaccessible Island, an extinct volcanic island, one of the Tristan da Cunha Island Group (and one of the most remote inhabited island groups in the world) in the southern Atlantic Ocean, several times. Inaccessible Island is particularly suited for study as it is uninhabited, is itself remote even within the Tristan da Cunha group and it is largely unvisited. Inaccessible Island is located in the Southern Atlantic ocean about two-thirds of the way to Africa as measured from Buenos Aires in Argentina. It’s about 2,534 miles to the east of Buenos Aires and about 1,735 miles west of Cape Town in South Africa.