There’s plastic litter at the bottom of the deepest ocean trench. Human destruction will outlive us all

More human beings have walked on the surface of the moon than ventured to the deepest point of the earth’s oceans. At over 10 kilometres deep, the Mariana Trench could swallow Mount Everest with a kilometre to spare.

This week “aquanaut” Victor Vescovo broke the record for the deepest dive by reaching 10,928 metres below sea level. Peering out into waters that would, if not for his protective submersible instantly crush him to a pulp, Victor initially found a landscape just as barren as those that the Apollo astronauts witnessed in the 1960s. But then life appeared. Tiny shrimps and fish eventually made an appearance.

And then a plastic bag and a sweet wrapper.

That plastic waste is being found in the most remote parts of the oceans should not be surprising. In 2015, over 300 million tons of plastic was produced. This continues a trend – the number has increased year on year as more products, and thus convenience, has driven our appetite for plastics. Plastics are polymers of linked chains of molecules produced from oil or gas. They are reanimated fossil carbon.

The qualities that makes them so useful – longevity and their lightness – has meant plastics have become the latest deadly weapon in humanity’s war on the rest of the biosphere. That the impact on our planet is merely collateral damage, the unintended consequences of our love affair with plastic, doesn’t matter to the many animals killed and ecosystems affected.

Blue Planet II opened many people’s eyes to the havoc plastics are producing in many marine ecosystems. Given their widespread use, plastics can easily escape waste streams. Often they are simply dumped. While refusing a plastic straw will have some, very limited impact on the amount of plastic waste produced, eating less fish would produce more change. In some regions, half of the ocean plastic waste is discarded fishing gear.

The plastic waste spotted by Victor Vescovo will eventually biodegrade. On average, plastic bags will disappear after a couple of decades. Plastic bottles may take several centuries. What is considered biodegrading is perhaps more accurately called bio-dispersing. As they age, plastic bags, straws, or bottles become brittle and fragment into tiny pieces. These pieces then become mixed with plankton at the base of the food chain.

Recent British research discovered nearly three quarters of animals recovered from six of the deepest points under the sea had plastics or microfibres in their gut. Plastics are literally everywhere in marine ecosystems.

Yet even if humanity suddenly decided to ditch plastic completely, our imprint on the earth system would still remain. One thought experiment is to consider what would happen if Homo sapiens were to become suddenly extinct. I will leave the manner of our demise to your imagination. Suffice to say that one day the sun rises on a planet that no longer features our particular species of intelligent ape.

Even our mightiest buildings would eventually crumble. The biosphere, while currently under onslaught from our ever-growing civilisation, would eventually reclaim the areas currently occupied by human cities or farms.

But humanity’s fingerprints on the earth systems would remain indefinitely. Our impacts on the earth system are now at such a scale that we have become a geological force. Our fabrication of not just plastics but novel chemicals that will not biodegrade means that there will be a thin layer of strange and exotic materials preserved in the rock record.

Concentrations of CO₂ in the atmosphere have just passed levels higher than any in the last three million years and will affect the chemical composition of ocean sediments. Perhaps most significantly of all, species across almost all ecosystems are becoming extinct. The biosphere may be entering a mass extinction event that the fossil record will bear testament to. Reflecting on these impacts, scientists have been considering whether to announce the new geological epoch as the Anthropocene.

If many millions of years after this apocalyptic vanishing of humans, aliens were to voyage to the earth, they would be able to detect our presence by simply looking at how the layers of rock suddenly changed much the same way we reconstruct the sudden disappearance of the dinosaurs by reading changes in the rocks formed at that time. The difference today is that humans are the asteroid.

Victor’s discovery of plastics at one of the most remote spots on earth should tell us that our time may be up if we do not rapidly begin to reverse our impacts. The earth will continue whatever we humans do. Even the biosphere will, given time, recover. But there are no guarantees that our civilisation can weather the consequences of its own waste.