Global plastic pollution could be approaching an irreversible tipping point

Catch of a large blue barrel floating on the ocean surface in the Great Pacific Garbage Patch by the German research vessel SONNE during expedition SO268 / 3, which crosses the North Pacific from Vancouver to Singapore in summer 2019. Photo credit: © Roman Kroke UFZ

Current rates of plastic emissions around the world can have effects that we cannot reverse, argues a new study by researchers from Sweden, Norway and Germany published in Science on July 2. According to the authors, plastic pollution is a global threat and actions to drastically reduce plastic emissions to the environment are “the rational policy response”.

Plastic can be found all over the planet: from deserts and mountain peaks to deep oceans and arctic snow. As of 2016, estimates of global emissions of plastic to the world’s lakes, rivers and oceans were between 9 and 23 million tons per year, with a similar amount being emitted to land annually. These estimates are expected to almost double by 2025, when business-as-usual scenarios apply.

“Plastic is deeply rooted in our society and gets into the environment everywhere, even in countries with good waste disposal infrastructure,” says Matthew MacLeod, professor at Stockholm University and lead author of the study. He says emissions are trending upward, although awareness of plastic pollution has increased significantly among scientists and the general public in recent years.

For Mine Tekman, doctoral student at the Alfred Wegener Institute in Germany and co-author of the study, this discrepancy is not surprising, because plastic pollution is not only an environmental problem, but also a “political and economic” one. She believes that the solutions currently on offer, such as recycling and cleaning technologies, are insufficient and that we need to get to the root of the problem.

Ten-foot plastic

A ten-foot macroplastic floating surface that was sampled by the German research vessel SONNE during expedition SO268 / 3, which crossed the North Pacific from Vancouver to Singapore in summer 2019. Source: © Gritta Veit-Köhler Senckenberg

“The world is promoting technological solutions for recycling and removing plastic from the environment. As consumers, we believe that if we properly separate our plastic waste, everything will be magically recycled. Technologically, plastic recycling has many limitations and countries with good infrastructure export their plastic waste to countries with poorer facilities. Reducing emissions requires drastic measures such as limiting the production of virgin plastic to add value to recycled plastic and banning the export of plastic waste unless it goes to a country with better recycling, ”says Tekman.

A poorly reversible pollutant in remote areas of the environment

Plastic builds up in the environment when the amounts emitted exceed amounts removed by cleaning initiatives and natural environmental processes, which occurs through a multi-step process known as weathering.

“Plastic weathering occurs due to many different processes and we have come a long way to understand it. But weathering is constantly changing the properties of plastic pollution, which opens new doors for further questions, “says Hans Peter Arp, researcher at the Norwegian Geotechnical Institute (NGI) and professor at the Norwegian University of Science and Technology (NTNU), who is also co- Author of the study. “Degradation is very slow and cannot effectively stop accumulation, so exposure to weathered plastic will only increase,” says Arp. Plastic is therefore a “weakly reversible pollutant”, both because of its continuous emissions and because of its environmental resistance.

Food waste filtered through plastic residue

Plastic residues are filtered from food waste collected in Norway after fermentation into biogas and soil fertilizer. Photo credits: Caroline Hansen and Heidi Knutsen, NGI

Remote environments are particularly at risk, as co-author Annika Jahnke, researcher at the Helmholtz Center for Environmental Research (UFZ) and professor at RWTH Aachen University explains:

“In remote environments, cleaning cannot remove plastic waste, and the weathering of large plastic objects inevitably leads to the formation of large numbers of micro- and nanoplastic particles, as well as the washout of chemicals that have been deliberately added to the plastic and other chemicals that make up the plastic-polymer. Break off the spine. So plastic in the environment is a constantly moving target of increasing complexity and mobility. Where it accumulates and what effects it can have is difficult or even impossible to predict. “

A potential turning point for irreversible environmental damage

In addition to the environmental damage that plastic pollution can cause from animal entanglement alone and toxic effects, it could also, when combined with other environmental stressors in remote areas, have widespread or even global effects. The new study sets out a number of hypothetical examples of possible impacts, including the exacerbation of climate change due to the disruption of the global carbon pump and the loss of biodiversity in the ocean, where plastic pollution acts as an added stressor for overfishing and ongoing habitat loss from change. B. water temperatures, nutrient supply and chemical exposure.

All in all, the authors see the threat that plastic emitted today could trigger global, poorly reversible effects in the future as a “compelling motivation” for tailor-made measures to reduce emissions significantly.

“At the moment we are polluting the environment with increasing amounts of poorly reversible plastic pollution. So far, we don’t see widespread evidence of bad consequences, but if plastic weathering has a really bad effect, we probably won’t be able to reverse it, ”warns MacLeod. “The cost of ignoring the build-up of persistent plastic pollution in the environment could be enormous. It makes sense to act as soon as possible to reduce plastic emissions into the environment. “

Reference: “The global threat from plastic pollution” by Matthew MacLeod, Hans Peter H. Arp, Mine B. Tekman and Annika Jahnke, July 2, 2021, Science.
DOI: 10.1126 / science.abg5433

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