Plastic pollution is one of the most prevalent environmental pollutants and a significant driver of climate change and biodiversity loss. But it is not just the cigarette butts and drinks containers littering beaches, turtles suffocating on discarded plastic straws and whale stomachs full of plastic waste. While extremely concerning, these visible impacts are the tip of the iceberg.
Plastic pollution has historically been conceptualised as ‘litter’, yet the reality is much more sinister, says a new report by the EIA (Environmental Investigation Agency). The total estimated weight of all fish in the ocean is currently around 700 million tonnes. By 2025, there will be an estimated 250 million tonnes of plastic in the oceans. By 2040, it could be almost 700 million tonnes, and by 2050 the weight of plastic will likely far exceed the weight of all fish in every ocean on earth.
The quantities of plastic present in some ecosystems are so high that they rival the quantity of natural organic carbon to the extent that plastic has been considered as a geological marker. The report cautions against another outcome of plastic pollution that could set off another pandemic, the plastisphere.
Plastisphere – A man-made threat to humanity
Bacteria, viruses and other life colonise the surface of plastic waste, creating distinct communities and population structures. Ecologists call this human-made ecosystem a plastisphere. At least 387 different groups of animals, plants and microorganisms live on the surface of floating plastic waste.
A variety of human and animal pathogens (diseases) form part of these surface-dwelling communities, so there is high potential for plastics to act as vectors for disease. Laboratory experiments have documented the transfer of bacteria Escherichia coli (E. coli) from the surface of microplastic to the gut of the Northern Star Coral. The bacteria Vibrio splendidus is commonly found on plastic waste and causes a deadly disease in oysters, clams and mussels that results in huge economic losses. These animals ingest Vibrio bacteria riddled microplastics as they filter seawater in search for food.
Spreading invasive species
Invasive (non-native) species are among the most important threats to biodiversity. Floating debris, including pieces of plastisphere, is now considered to play an important role in spreading these species. For example, more than 80% of invasive species in the Mediterranean may have arrived on floating plastic waste. This is particularly problematic for remote islands which naturally have higher levels of endemic species that are more at risk from invasive species transported in this way.
There is strong evidence that the micro-communities living on plastics are responsible for helping to spread antibiotic resistant genes globally. As the community of microorganisms living on the surface of plastic waste (the plastisphere) is so diverse, with many hundreds of different species, there are higher rates of what is called ‘horizontal gene transfer’ (HGT). Bacteria, for example, can trade slices of genetic code between one another horizontally – i.e. between one another directly. HGT is a key process by which antibiotic-resistant genes, a long recognised threat by the World Health Organization, come into being.
What should be done?
Calls for a legally binding treaty on plastics have now reached fever pitch. Since the inaugural United Nations Environment Assembly (UNEA) in 2014 there have been
four successive resolutions on the topic of plastic pollution. UNEA-3 saw the initiation of the Ad Hoc Open-Ended Expert Group on Marine Litter and Microplastics (AHEG) (2018-20) to explore policy response options at the global level. After the conclusion of the expert group’s mandate, member states organised a Ministerial Conference on Marine Litter and Plastic Pollution, an output of which was a Ministerial Statement calling for a new global agreement, now signed by 71 countries.
In total, based on the entirety of ministerial statements, country-and regional-level declarations and communiques, it is estimated that more than 100 countries have expressed support for treaty negotiations to begin. For this to happen, however, the EIA report says that a resolution must be passed at UNEA-5.2 (scheduled for February 2022). Securing the right mandate is absolutely critical to the efficacy of any future plastics treaty.