Majority of plastic debris on Seychelles beaches from far-off sources, study concludes |21 January 2023

The vast majority of plastic debris and waste that end up on Seychelles’ beaches are from “far-off sources”, according to a new modelling study led by the University of Oxford.

Results of the study were published in the Marine Pollution Bulletin on January 18.

Key findings are that Indonesia, India and Sri Lanka are among the main sources of land-based plastic debris found on  beaches in Seychelles, especially medium-large debris that have a high buoyancy  such as bottle caps, sandals, bottles and small domestic items.

Plastic debris from Indonesia would have been at sea for at least 6 months, and even over two years.

Additionally, as has been observed by various local stakeholders, a significant amount of plastic debris originates from fisheries-related activities and shipping lanes. This includes discarded or lost fishing gears.

While smaller debris, such as millimetre-sized plastic fragments and pellets tended to originate from within the country itself, or from East Africa, the large numbers of bottles beaching on Seychelles’ islands which come from Malaysia, Thailand, and China as indicated by the labels, are probably discarded from ships as opposed to floating in from those countries.

For some islands, a considerably higher proportion of plastic waste comes from marine sources, rather than land.

Researchers further concluded that the rates of plastic debris accumulation showed a strong seasonal affect, with plastic debris most likely to land on Seychelles’ beaches towards the end of the Northwest monsoon, between March and April, whether from land or marine sources.

The accumulation of such debris is also likely to be amplified by the El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD, also known as the Indian Niño) events.

The study, for which the focus was the sources of land-based and marine types of plastic pollution, investigated this by developing a high-resolution model that simulated the movement of plastic debris across the world’s oceans. Input data including waves, winds, oceans currents and plastic debris entering the ocean from coastal populations, rivers and fisheries were used to predict plastic accumulation at 27 sites in Seychelles and the wider Indian Ocean.

It combined observational data from across Seychelles with cutting-edge computer simulations, to generate the predictions, and is the first study to produce a quantitative estimate of the sources of plastic for the Seychelles islands and other remote islands in the Western Indian Ocean.

The researchers note that such plastic pollution is a significant environmental threat, both for the marine ecosystems and the communities that depend on the ocean for food, tourism, and other economic activities. The debris drifting from far-ff sources also increases the risk of spreading invasive species and diseases.

Lead author of the research, Noam Vogt-Vincent, said that the study will help to provide vital information for local management, and to inform national and international responses.

The researchers add that the result illustrates the sheer scale of the plastic pollution challenge which small island developing states face, highlighting the urgent need for a global plastic treaty.

The findings also build on that of an earlier study, also led by the University of Oxford, which estimated that over 500 tonnes of debris had accumulated at the Unesco World Heritage Site, the Aldabra atoll.

Greater enforcement of policies which forbid the disposal of fishing gear and plastics at sea and investment in waste management systems within the main source nations is crucial towards addressing the problem, the study claims, as is the implementation of waste disposal, to prevent land-based litter from drifting to remote island sites.

Co-author Dr April Burt of the Seychelles Islands Foundation and University of Oxford said that the islands “are faced with the deeply inequitable situation of bearing the costs of removing waste they were not responsible for generating, contrary to the ‘polluter says’ principle”.

The study, which also involved researchers from the University of Montpellier, the Institut de Recherche pour le D’eveloppement, MARBEC, and the Okinawa Institute of Science and Technology should be the first step towards accountability and prevention, Dr Burt added.

Compiled by Laura Pillay

Photo sources: Seychelles Islands Foundation