Cans and bottles collected for research on a remote beach in De Hoop Nature Reserve. (Peter Ryan)
Plastic lids and bottles tell a compelling story about the origins of trash on South African beaches.
A recent study by researchers from the University of Cape Town's Fitzpatrick Institute for African Ornithology and Nelson Mandela University revealed surprising differences in how these objects travel and accumulate on beaches.
The study sampled lids and bottles from 21 different beaches and revealed clear patterns in their origin and distribution.
Research has shown that water and soft drink bottles made from polyethylene terephthalate (PET) would sink in the ocean if they didn't contain air, but their caps are made of a polymer that can float and drift long distances.
The study was published in the journal Marine Pollution Reportfound that the proportion of foreign-made bottles and lids correlated and increased with distance from urban areas, indicating that “much of the land-based litter washes up close to its source.”
Evidence found on islands and mainland parts of the Southern Hemisphere indicates that most foreign-made plastic bottled drinks wash ashore within one to two years of production, “too early to have been washed ashore from their countries of manufacture (mainly China) and are being illegally dumped from ships.”
More than 80 percent of foreign-made drink bottles and 90 percent of the caps originated in Asia. Most of the bottles were manufactured in China (55%), Malaysia and Singapore (25%), and the United Arab Emirates (7%) and were dumped from ships. In contrast, most of the caps were in poor condition after being transported across the Indian Ocean from Indonesia by the South Equatorial Current.
Researchers collected more than 13,200 bottle caps from 20 beaches along South Africa's southwest coast, spanning 62.5 kilometres (40.5 miles) of land, including 7,236 bottles found along 66.8 kilometres (41.5 miles) of coastline.
Excluding replicate samples, the density of uncapped bottles was nearly twice that of bottles, even though 60% of the bottles had caps. The density of caps varied widely across beaches, ranging from 9 to 9,600, and was much more numerous than that of bottles.
“On most beaches the density of caps exceeded the density of bottles. Only two beaches – Cape Recife and Pollock Beach in Gouebera, just outside Cape Town – had more bottles than caps, and three beaches in St Helena Bay had almost five times as many bottles as caps,” the report said.
Drink bottle caps were common at all beaches (range 63%-89%) but were most prevalent at urban beaches.
More than eight times as many lids as bottles were collected at Muizenberg Beach between April and 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 closures could be classed as of domestic or international origin, representing 85% of beverage closures and 24% of other closures. The proportion of closures manufactured in South Africa is higher than for bottles (78%).
Lead study author Peter Ryan, professor emeritus at the Fitzpatrick Institute of African Ornithology, said refrigerated drink bottle caps typically don't have dates marked on them.
“However, some companies run promotional contests and these lids can be dated quite accurately, with lids regularly found dating back to the 1980s,” Mr Ryan said.
Every three months, he collected caps and bottles from two somewhat remote beaches in the Koeberg Nature Reserve and in the Cape of Good Hope area of Table Mountain National Park.
“I was mainly interested in documenting where they came from, because most of the foreign bottles came from ships, while most of the lids are long-distance drifters, mainly from Indonesia. But we found that even though we were cleaning the same beaches every three months, we were still finding very old lids,” he said.
“We have a huge problem with rubbish, especially small items like lids that end up in landfill. We go back in three months and the wind has blown and the tide has risen. [and] We found a lot of lids, some of which are 30 or 40 years old.”
This indicates the beach is a long-term site of sediment accumulation, he said.
On urban beaches, exotic lids made up 4% of the total, with a higher proportion in Gouebera (12%) than in Cape Town (3%). Peri-urban beaches around Gouebera (33%) had a significantly higher proportion than Cape Town (11%). On more remote beaches, the four south coast beaches had more exotic lids (26%) than the west coast (10%) or St Helena Bay beaches (1%).
In the northernmost Namaqua National Park, the proportion of foreign caps compared to bottles was particularly low, while Sodwana Bay had the highest proportion of foreign caps.
There were seven times as many Chinese-made drink bottles found without caps, while more than 1,000 Indonesian-made bottles were found without any caps at all.
“Among the multinational beverage companies, Coca-Cola had more than twice as many foreign-made closures as bottles, and most of the bottles were made in China, while most of the closures were small and probably came from Southeast Asia,” the report said.
Coca-Cola products dominate South Africa's drink closures, accounting for at least 60 percent, but “most Coca-Cola closures still have ink labels that have been lost from many of the older closures,” he said.
“The percentage of locally produced Coca-Cola closures (96%) was roughly the same as the percentage of bottles (94%). There were at least 3.6 Coca-Cola closures per bottle, which is roughly the same as the percentage of other beverages with branded closures.”
Two brands sold in the Cape Town area, Twizza and Double O, were found to have between 30 and 33 lids per jar on two Table Bay beaches due to “extremely high lid density”.
In the 1980s, bottles outnumbered bottle caps on South African beaches, but since then, bottle caps have become “increasingly prevalent” — contrary to a global trend shown by the annual International Coastal Cleanup (ICC), which collects beach litter data from more than 100 countries.
Overall, in the first 25 years of the ICC (1986-2010), the number of bottle caps outnumbered the number of beverage bottles by 42%, but the number of bottles has exceeded the number of lids every year since 2013. “Despite an increasingly large number of bottles over the past decade, South African ICC data shows that the number of lids has exceeded the number of bottles in nine of the past 10 years, with an average of 1.5 lids per bottle,” the study said.
This is despite the fact that most of the bottles still have their caps on: “One reason for the excessive amount of caps is that caps are more easily dispersed than bottles that leave land, and once in the ocean, caps are more likely to be dispersed over a larger area due to their buoyancy.”
Also, because sweeps and litter traps are generally more effective at treating larger debris, the number of bottles removed by cleanup efforts, both at source sites and on shorelines, is likely to increase proportionately.
