Sea birds’ fate: death by plastic
Cape Town - So how many albatross chicks have you killed in recent years? The indignant response of almost everyone to that question would be “none, of course” – particularly as many of them are unlikely ever to have encountered these magnificent ocean wanderers, other than perhaps through studying Samuel Taylor Coleridge’s epic poem The Rime of the Ancient Mariner at school.
But, as UCT scientist and seabird expert Dr Peter Ryan explains in the latest issue of African Birdlife, we are all indeed to blame, if indirectly, for the deaths every year of millions of creatures that include seabirds like albatrosses, prions and petrels.
This is because of our indiscriminate use and particularly disposal of myriad plastic products that have become essential to our modern lives.
Ryan, an associate professor at UCT’s Percy FitzPatrick Institute of African Ornithology, has an impeccable track record in the field: he studied the impacts of plastic ingestion on seabirds for his Master’s degree in the 1980s, and initiated programmes to monitor the amount of marine litter around South Africa, which he continues to this day.
There are now so many kinds of plastics and plastic products that life without them is almost inconceivable, he says. We manufacture on a global scale some 260 million tons of plastic every year, and use about eight percent of the total oil production to do this.
“But many of the properties that make plastics so versatile also predispose them to becoming environmental pollutants, and the low density of most plastics allows them to be readily dispersed by water and even the wind, carrying them far from their source areas. Added to this, synthetic polymers are largely impervious to biological decay, breaking down slowly only when exposed to ultraviolet radiation.”
Plastic litter kept under water or buried may survive intact for hundreds or even thousands of years, and plastic pollutants are now found around the globe – from remote beaches in Antarctica in the south, and all the way to the Arctic seabed in the north.
A particular problem is the ingestion of plastic fragments by seabirds – first recorded by New Zealand scientists in 1960 – either directly or indirectly through their prey: small filter-feeding fish that can’t distinguish plastic from the microscopic animals called zooplankton on which they normally feed.
“In some mid-ocean gyres, plastic fragments are now several orders of magnitude more abundant than zooplankton,” he says.
Seabirds become entangled in plastic litter such as discarded packaging loops, fishing gear, ropes and bands, but the widespread occurrence of plastic ingestion is a more serious problem. The plastic may block or damage birds’ digestive tracts, and/or accumulate in their stomachs, reducing their capacity for food and hence their nutrient intake.
“This can be acute in some species, like North Pacific albatross chicks, which are fed so much plastic that they die.”
Off southern Africa, more than 90 percent of Great Shearwaters and Blue Petrels have plastic fragments in their stomachs. The most significant problem, Ryan explains, is the accumulation of toxins like PCBs (polychlorinated biphenyls), DDT and HCHs (hexachlorocyclohexanes) and other “POPs” – persistent organic pollutants – carried by some of the plastics birds ingest. Other toxins include flame-retardants and colourants that also negatively affect birds’ metabolisms.
“This has been an area of much recent research, given concerns about the impacts (of these pollutants) on humans. The results are worrying, because even very low concentrations of some of these substances can seriously affect animals,” he says.
Southern hemisphere confirmation of the dire state of affairs comes from the archipelago of Tristan da Cunha, which in 2009 experienced a sudden spike in the amount of plastic ingested by storm petrels and prions over amounts recorded in the mid-2000s. This suggests there’s been an absolute increase in the amount of plastic in the sea in this area, argues Ryan.
“Tristan lies just south of the South Atlantic gyre, where floating plastic accumulates. If we continue pumping plastic into the environment, we might soon face a similar situation to the infamous North Pacific ‘garbage patch’ on our doorstep,” he warns.
According to Wikipedia, this massive area of pollutants in the North Pacific ocean gyre was predicted in a 1988 scientific paper by the US’s National Oceanic and Atmospheric Administration (NOAA), and subsequently confirmed by research.
Its size is unknown because large items readily visible from a boat deck are uncommon, and most debris here consists of small plastic particles suspended at or just below the surface, making it impossible to detect by aircraft or satellite. But estimates range from 700 000km2 to more than 15 million square kilometres – between 0.41 percent and 8.1 percent of the entire Pacific Ocean – while another estimate puts it at twice the size of the continental US.
Clearly there’s a need to reduce the amount of plastic waste entering the sea, Ryan says. “Although people like to place the blame on ships at sea, by far the majority of marine litter derives from land-based sources. We are all responsible, and can make a difference by changing the way we consume plastics and dispose of them.”
* African Birdlife is the bi-monthly magazine of non-government conservation group BirdLife SA, available at CNA, Exclusive Books and other outlets. To get free copies, become a member of BirdLife. Visit http://www.birdlife.org.za