The Fight Against Plastic Pollution

This month is Plastic Free July – a key initiative of the Plastic Free Foundation and a global movement that helps millions of people be part of the solution to plastic pollution. Here we highlight some of the incredible projects our researchers and students have been involved in, for trying to tackle this global problem.

Aldabra…just one reason to reduce single-use plastic!

The remote Aldabra Atoll is one of the world’s largest raised coral atolls comprised of 4 main islands that are part of the outer islands of the Seychelles. In 2019 students from The Queen’s College, Oxford (including Earth Sciences collaborators and NERC DTP students!), took part in a clean-up operation and helped to remove 25,570kg of marine plastic pollution over a period of 5 weeks (see the full clean-up project report here).

Check out the documentary below that has been made about the Clean-Up Project:

“It is estimated that 8 million tonnes of plastic pollution is spewing out of rivers into the oceans each year. This plastic is moved around the oceans by currents and wind until it is intercepted by land. In the Indian Ocean, the coastlines of small island states like the Seychelles act as nets where vast quantities of plastic pollution are captured. As such, the Aldabra coastline, left untouched and almost un-visited, is clogged with plastic waste.”  (Excerpt taken from The Aldabra Clean-Up Project Report).

Helen Johnson (Associate Prof. of Physical Oceanography) sheds light on the possible source of Aldabra’s plastic pollution here:

‘Our role has been to use an estimate of the surface ocean currents to figure out where the plastic pollution is coming from.  We track virtual particles backwards in time from Aldabra for two years.  Figure 1 shows the likelihood that a particle has passed through any given location during that time.  You can see that most of the particles seem to be coming from the east coast of Africa, but take a rather circuitous route to get there, being swept east out into the Indian Ocean before moving southwards and then west again to arrive at Aldabra. South India and Sri Lanka also seem to be potential sources.

Figure 1

Figure 2 shows the schematic of the circulation (taken from Lynne Talley’s book “Descriptive Physical Oceanography”).  You can see the various currents involved here – the key currents are the South Equatorial Countercurrent, which carries the plastics east from Africa, and the South Equatorial Current, which brings them back west towards Aldabra.

Figure 2. Image reproduced from “Descriptive Physical Oceanography” by Lynne Talley

There are a few key caveats of these preliminary results!  First, the surface ocean currents and wind directions in this region change dramatically with the monsoons, which may affect the pathways and sources of the plastic. There’s likely to be variability in the ocean circulation from year to year too. For now we have just looked at plastic arriving at Aldabra in December 2017.

Second, on longer timescales other sources might become apparent.  When we started this, I expected to find that the plastics were coming from Indonesia.  We don’t see this with 2-year trajectories, but perhaps would if we tracked further back in time and/or looked at different seasons, so it’s a work in progress!

The goal though, is to establish where the plastics (which are mostly domestic products like flip flops, bottles, toothbrushes etc.) are coming from so that we could potentially tackle the problem at source.  Can we help the countries responsible to turn off the tap so that Aldabra’s beaches stay clean into the future? The clean-up team are hoping to be able to get some clues as to the source of the pollution from labels, trademarks, styles and perhaps the type of plastic used.  That will give us some data to compare with and help make the case.’