The second of the new AWG articles is Jan Zalasiewicz et al., “The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene,” online-only as yet in Anthropocene.
The paper’s aim is to put “current knowledge about the environmental behaviour of plastics into a general geological perspective,” write the 17 authors. So how do you think about plastic waste not so much as litter or as pollution, but as a geological phenomenon? By fading out on a foreground image of plastic bags flapping in hedgerows, and tuning in to something deeper and wilder and stranger: by another one of those vertiginous changes of scale that are so characteristic of thinking about the Anthropocene. Thinking geologically about plastics means considering them both as a single huge global stockpile and as trillions of tiny threads, sun-decayed, wave-shredded, and surviving for geological ages in beaches and deltas and seabeds.
Plastics haven’t been discussed that much before now by writers on the Anthropocene. The only paper that came to mind for me was this one, which coined the word “plastiglomerate” for plastic litter fused into rock. It described that fusion taking place in campfires on a Hawaiian beach, and identified the resulting hybrid as a novel kind of stone, one that might survive for geological timespans. But the new Zalasiewicz et al. paper takes us off from that beach right around the world. Its most resonant theme is the mobility of plastic (as compared to other mass-produced human-made substances like glass and ceramics), its effervescent circulation into nearly every kind of environment.
A few things I learned: about a quarter of a million tons of plastic are afloat in the ocean right now (most litter entering the seas is plastic); hermit crabs on Diego Garcia use plastic bottle tops as homes; five billion tons or so of plastic has been produced in total so far, and the amount produced each year weighs about as much as all living humans; 8% of global oil production is used to make the stuff; there are ten thousand rayon fibres in a cigarette filter tip. Everything’s interconnected: plastic in the Pacific gets frozen away in Arctic sea ice, but that means that Arctic melting “at current rates could unlock over one trillion pieces of microplastics over the next decade.” Evolution, too: communities of microbes form on oceangoing plastic, and a few seem to be able to eat it, so evolutionary pressures should mean there’ll one day be many more plastivores.
The paper gives us a global ecology of plastic that has, now and then, a kind of eerie imaginative beauty to it. Some thousands of plastic fibres are released invisibly from every washing machine-load of synthetic clothes; they “travel far by river and sea current,” not usually stopping on the continental shelf, but instead flowing on downstream through submarine canyons until burrowing animals finally bury them a few centimetres deep within the abyssal plain; or they’re gradually gathered and concentrated by “the slowly circulating waters of the North Pacific central gyre … [or] the other great gyres of the world”—as, I suppose,
the great Spirit with plastic sweep
Moves on the darkness of the unformed deep.
Accumulations of plastic litter have already been put to practical use as a way of dating sediments: they’ve been studied in order to put a date on floods on the coast of Oman. Could plastics also be fixed on as the stratigraphic marker that would define the base of the Anthropocene epoch? Probably not, the paper concludes, but they may well be fossilizable under the right conditions (mostly buried undersea), and if so quite easy to find within the samples taken by the imagined geologists of the distant future. The crucial survivors wouldn’t be the occasional plastic bags so much as that infinite multitude of millimetre-scale or smaller “microplastics,” which should be scattered through the sedimentary record just like the abundant microorganisms that are geologists’ usual stock in trade. “[Plastics’] fossilization potential once buried in strata,” Zalasiewicz and co. write with lovely sincerity, “is a topic of considerable academic interest, although of no analytical study yet, as far as we are aware.”
The downside is the familiar one among most proposed markers for the Anthropocene series. The global dispersal of plastics multiplied rapidly at the time of the mid-twentieth-century Great Acceleration, but not in so abrupt a way that one single year stands out as the moment when the character of plastic-bearing sediments changed. That annual resolution (to 1952) is the crucial advantage that the beginning of worldwide plutonium fallout from nuclear tests has over other candidates—although it’s just possible that the emergence of some specific new type of plastic, like acrylic fibres, could indeed be picked out as a single-year marker.
But when plastics are “considered not only as environmental pollutants, but also as contributors to the character of recent (generally post mid-20th century) and contemporary strata”—when they’re thought about geologically, in other words—a couple of other things are achieved. First, under the right conditions they could be a useful if not totally precise “practical indicator” of Anthropocene-epoch, mid-twentieth-century-or-later sediment layers. Second, one new facet of the modern world’s ecology catches the light for the first time: an immense worldwide dance of particles and filaments of plastic, too small for the eye, seething and settling through all the flows of matter that help make up the earth system.
More to follow!
Made Ground 