/ 29 June 2024

Plastics lids an ‘increasingly dominant’ pollution source on South Africa’s beaches

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Canisters and bottles collected for the study at a remote stretch of beach in De Hoop Nature Reserve. (Peter Ryan)

Plastic lids and bottles tell a compelling story about the sources of beach litter on South Africa’s coastlines. 

A recent study by researchers at the FitzPatrick Institute of African Ornithology at the University of Cape Town and Nelson Mandela University reveals surprising differences in how these items travel and accumulate on beaches. 

By sampling loose lids and bottles at 21 different beaches, the study uncovered distinct patterns in their origins and dispersal.

According to the the study, water and soft drink bottles made from polyethylene terephthalate (PET) sink at sea unless they contain trapped air, whereas their lids are made from polymers that float and can drift long distances. 

The study, published in the journal Marine Pollution Bulletin, found that the proportions of foreign-made bottles and lids were correlated, and increased away from urban centres, indicating that “much land-based litter strands close to source areas”.

Evidence from island and continental sites in the Global South suggest most foreign PET drink bottles are stranded within one to two years of manufacture, “too soon for them to have drifted from the country of manufacture — mainly China — indicating that they are dumped illegally from ships”.

More than 80% of foreign-made drink bottles and 90% of lids originated from Asia. Most bottles were made in China (55%), Malaysia and Singapore (25%) and the United Arab Emirates (7%), and were dumped from ships. By comparison, most loose lids were in poor condition after being carried across the Indian Ocean from Indonesia by the South Equatorial Current

The researchers collected more than 13 200 lids from 62.5km of beach at 20 beaches along South Africa’s south-west coast. The same beaches yielded 7 236 bottles from 66.8km of coastline.

Excluding repeat samples, the density of loose lids was almost double that of bottles, even though 60% of bottles had lids. The density of lids varied enormously among beaches from nine to 9 600 lids, much more so than bottles.

“Lids occurred at higher densities than bottles at most beaches; bottles only outnumbered lids at the two Cape Town peri-urban beaches, Cape Recife and Pollock Beach in Gqeberha, and especially the three beaches in St Helena Bay, where bottles were roughly five times more abundant than lids,” the report said.

Lids from drink bottles dominated at all beaches (63% to 89%), but were most common at urban beaches. 

Over eight times more lids than bottles were collected at the Muizenberg beach from April to July 2020. At Sodwana Bay, 1 864 lids and 86 bottles were collected, of which 1 124 lids and 80 bottles were collected during frequent sampling.

Overall, 72% of lids could be assigned to a local or foreign source — 85% of drink lids and 24% of other lids. A higher proportion of lids was made in South Africa (78%) than bottles.

Lids from cooldrink bottles are not generally well marked for dates, said the study’s lead author Peter Ryan, an emeritus professor at the FitzPatrick Institute of African Ornithology.

“But some of the companies have promotional competitions … Those lids can be dated quite accurately and we find lids going back to the 1980s regularly,” Ryan said.

Every three months, he collected lids and bottles on two semi-remote beaches at Koeberg Nature Reserve and in the Cape of Good Hope section of the Table Mountain National Park. 

“I was mainly interested in just documenting where they were coming from because most of the foreign bottles come from ships, whereas most of the lids come from long distance drift from Indonesia, primarily. But it turned out that even though we were cleaning the same stretches of beach every three months, we were still finding these really old lids,” he said.

“There’s this whole problem with legacy litter, particularly for small things like lids that are usually buried. You go back three months later and the wind has blown or the tide has been high [and] you find a whole bunch of lids and some of them are 30, 40 years old.”

This shows that beaches are long-term sinks, he said.

Foreign lids accounted for 4% of lids at urban beaches, with a higher proportion at Gqeberha (12%) than Cape Town (3%). The proportion at peri-urban beaches around Gqeberha (33%) was substantially higher than Cape Town (11%). At the more remote beaches, the four South Coast beaches (26%) had more foreign lids than West Coast (10%) and St Helena Bay beaches (1%). 

The proportion of foreign lids was particularly low relative to bottles at the northernmost site, Namaqua National Park, whereas Sodwana Bay had the highest proportion of foreign lids.

Chinese-made drink bottles outnumbered loose lids 7:1 whereas more than 1 000 Indonesian lids were found without a single bottle. 

“Among multinational drink companies, there were more than twice as many foreign-made lids from The Coca-Cola Company than bottles, with most bottles from China, whereas  most lids were smaller and probably came from South East Asia,” the report said.

Among South African drink lids, products from The Coca-Cola Company dominated, accounting for at least 60%, “even though most Coca-Cola lids have inked labels that are lost from many older lids”. 

“The proportion of locally-manufactured Coca-Cola lids (96%) was similar to that of bottles (94%). There were at least 3.6 loose Coca-Cola lids for every bottle, similar to the ratio for other drinks with branded lids.” 

Two brands sold in the Cape Town area — Twizza and Double O — had 30 to 33 lids per bottle, because of the “very high densities of lids” on the two Table Bay beaches. 

In the 1980s, bottles outnumbered lids on South African beaches, but since then, lids have become “increasingly dominant”. This runs counter to the global trend shown by the annual International Coastal Cleanup (ICC), which collates beach litter data from more than 100 countries.

Overall, bottle caps outnumbered drink bottles by 42% during the first 25 years of the ICC (1986–2010), but bottles have outnumbered lids every year since 2013. “Despite this increasing dominance of bottles over the last decade, the ICC data for South Africa show more lids than bottles in nine of the last 10 years, with on average 1.5 lids per bottle,” the study said.

This occurs despite most bottles still having their lids attached. “The excess of lids probably results in part from lids dispersing more easily than bottles from land-based sources. And once in the sea, lids may disperse more widely because of their inherent buoyancy.” 

It is likely, too, that proportionally more bottles are removed by cleaning efforts, both in source areas and on beaches, because cleaning and litter traps typically are more effective for larger litter items.