For thousands of years humans have existed on Earth, but it is only in the last 100 or so that plastics have entered our lives. These days you can barely go a minute without touching something made from some kind of plastic. But while we've been getting all swept up in the convenience that synthetic polymers bring us, the trash has been piling up. Millions of metric tons of plastic enter the ocean every year, and no one really knows where it is and what damage it is causing. So ... what are we to do about it?

Before we dive on in, a few not-so-fun facts about plastic. According to the Environmental Protection Agency, as many as one trillion plastic bags are used worldwide every year and less than five percent are recycled. Every 11 years, our production of plastic doubles, and over the coming 11 years we'll produce more plastic than we've made since we started.

In 2015, a paper published in the journal Science estimated that somewhere between 4.8 and 12.7 million metric tons of plastic enter the ocean each year. The researchers arrived at this figure after estimating how much plastic waste every coastal country in the world produces, and then calculated how much could wash into the sea from open dumps and improperly secured landfills. The scientists guess that this amounts to between 15 to 40 percent of all disposed plastic. But where it is now and in what form is something of a mystery.

Breaking it down

What makes the ocean plastic so hard to track is the fact that it doesn't remain in the form of things like bottles, lighters and bags. It is broken down into small fragments known as microplastics, which are tinier than the fingernail on your pinky. Somebody who has as good a handle on this problem as anyone is Erik van Sebille, an ocean scientist at Utrecht University in the Netherlands. Last year he led a study that aimed to calculate how much microplastic was floating around on the surface of the ocean.

The research used all available measurements of microplastic and combined it with three different numerical ocean circulation models, arriving at an estimate of somewhere between 93,000 and 236,000 metric tons. The broad range, the researchers noted, was due to the fact that huge parts of the ocean are yet to be sampled for plastic debris.

But the rough estimate is enough to give them an idea, and the researchers say that the floating microplastic accounts for roughly one percent of all plastic waste in the ocean, which is a scary thought. Where is the rest of it, and how do we know what damage it might be causing? And how do we fix the problem if we don't even really understand it?

"That is one of the big, big questions we have now within our field is, really where is all the plastic?" Sebille tells New Atlas. "It's a bit like what the astronomers have with with their dark matter and their dark energy. We've have really only accounted for one percent of all the plastic in the ocean.

"So we don't know where all of this plastic, 99 percent of it, is," he continues. "We don't know how much of it is on the seafloor, we don't know how much of it is on the coastlines or beaches, trapped in mangrove forests those kinds of things, and we don't know how much is in the guts of marine animals and organisms. As long as we don't know that, we don't know where marine life interacts with those plastics and we also don't know where is best to take out the plastic or to clean it up."

An island of waste

One place where we do know there to be a whole lot of plastic is a Henderson Island Jennifer Lavers

One place where we do know there to be a whole lot of plastic is Henderson Island, a deserted atoll in the middle of the southern Pacific Ocean. Research scientist Jennifer Lavers from the University of Tasmania led a recent expedition to the island, where the highest density of plastic waste anywhere on the planet was waiting for her. She estimates that a total of 37.7 million pieces had washed up and spread out over the uninhabited island, and that as many as 13,300 new pieces arrive every day.

"If Henderson Island has taught the world anything, it's that not all of the impacts that humans have on the planet are difficult to visualize," she tells us. "While climate change, ocean acidification, and sea level rise are difficult to 'see,' plastic is very much in our faces. Even on far-flung islands that we once thought were out of sight, out of mind. Our wasteful habits are coming back to haunt us, in a big and undeniable way. But, as much as that may alarm some members of society, the truth is, once again, it's the small stuff that you can't see that you should be most worried about."

The plastics that we cannot see may indeed be what unsettles the scientific community most. But what Lavers alludes to here is not just the tiny pieces floating around somewhere in the ocean, but the byproducts of those pieces being broken down.

"Think CFCs or DDT," says Lavers. "You can't see them, but I assure you, they're bad news. The exact same can be said for plastic. What you can see with the naked eye is only the tip of the iceberg. Chemicals, potentially hundreds or even thousands of them, the majority of which we know very little about, especially how they interact with one another, adhere or absorb onto the surface of plastic items that are floating in the ocean. This is in addition to the hundreds or even thousands of chemicals used in the manufacture of plastics that, once again, we know little about their safety for humans and especially the marine environment."

Getting to work

It does start to feel like one of those situations where the more we learn about the problem, the more we realize we don't know. Addressing this is the immediate focus of Sebille's upcoming research. He has secured funding from the European Union to develop 3D distribution maps of all plastic moving through the ocean. Sounds like a tough ask.

"It is a massive task, and every time I think about it, it kind of scares me," he says with a laugh. "The basic idea is that we already have a pretty good understanding of how the ocean moves stuff around and we have a reasonable understanding of where the plastic enters the ocean. So really what we want to do is make a virtual simulation of all the plastic moving through the ocean. What we need to find out first is how quickly does plastic fragment, how quickly does plastic sink? And where and how does it get ingested by animals? Essentially what we are going to do is create a giant computer simulation, a computer game, of the plastic through the ocean."

While Sebille goes about mapping plastic's movement through the ocean, some are going right ahead and trying to clean it up. University drop-out turned inventor Boyan Slat has turned quite a few heads in the four years since he started his Ocean Cleanup Project, having raised millions in funding, carried out feasibility studies and aerial surveys of the plastic garbage in the ocean.

Boyan Slat's Ocean Cleanup Project aims to collect plastic waste with huge floating arms The Ocean Cleanup

The basic premise is to place huge floating arms in the water to passively collect waste using the ocean's gyres, which are natural wind-driven current systems that also play host to huge accumulations of plastic. Slat plans to test his latest design off the American west coast later this year, and believes he can clean up half of the Great Pacific Garbage Patch within five years of deployment. The company has raised US$21.7 million in funding in the last six months alone, including donations from notable philanthropists Peter Thiel and Marc and Lynne Benioff. But not everyone is convinced.

"The public may think this sounds like a great idea, but hundreds of highly qualified scientists around the world do not," Lavers tells us.

These scientists see more than a few holes in the Ocean Cleanup Project's approach, although the team has sought to address one of the major flaws with a recent redesign. Originally, the plan was to anchor the booms to the seafloor at a depth of 4 km (2.5 mi), which not only goes far beyond what is currently possible in terms of mooring, but would make the system very vulnerable to storms.

"There's no material on Earth that we know of that can withstand the pressures that those giant booms would be subjected to," says Sebille, who attended the launch of the Ocean Cleanup Project's new design last month. "So rather than anchor them to the ocean floor four kilometers down, they are making them float, and more mobile. And that reduces a lot of stress, a lot of the strain, and they also say that they are more efficient this way."

An underwater view of one of The Ocean Cleanup Project's booms Erwin Zwart/The Ocean Cleanup

The new design will still use anchors, but only at a depth of 600 m (2,000 ft), so the system will drift along with the current, but more slowly than the plastic it is trying to catch. Below the floating boom will hang a solid screen that is claimed to collect plastic as small as one centimeter in size and as large as discarded fishing nets that are meters long. But even if Slat and his team do get these contraptions up and running, there are serious question marks over how much of a difference they will actually make.

Like peeing into the ocean?

Stiv Wilson is the Director of Campaigns at environmental non-profit The Story of Stuff project and long-time ocean activist who has visited four of the five "garbage patches," the accumulation zones of plastic that form at the ocean's five subtropical gyres. He also spearheaded a movement to ban microbeads, the tiny plastic balls used in toothpastes and face creams that also wind up in the ocean, which ultimately led to Barack Obama signing The Microbead-Free Waters Act in 2015.

He is of the view that the plastic problem is most definitely not something that can be reigned in with a few carefully-placed booms. And The Ocean Cleanup Project itself does acknowledge that solving this problem will take a variety of approaches, but its stance is that we do need to clean up what is already there, and that these booms are the best way to do that. Wilson isn't so sure.

"What Slat fails to address is how the gyres actually work," he tells us. "For instance, the North Pacific Gyre jettisons about 50 percent of its contents every orbit, which takes about three years. That means the plastic leaves the gyre and will either end up on shore, or in another gyre. So, it seems to me that all we need to do is stop plastic from getting into the ocean in the first place and clean our beaches as it washes up.

"With the amount of plastic being produced at an exponentially higher rate, it stands to reason that some portion of this will continue to leak into the ocean, which means, the problem will continue to grow unless the leak is stopped, which also means that if Slat's branded oil boom contraption does work, and that is a big if, it will need to also grow and grow and grow. That's not a solution, that's a dog chasing its tail."

A little problem called bycatch

Wilson says these booms will prove ineffective against the 95 percent of the microplastic in the ocean, which is smaller than a grain of rice. But there are not only concerns that the Ocean Cleanup Project will have a negligible impact, there are fears that it will actively harm the environment by trapping marine life in its floating arms. This includes larger species like whales and turtles, but of particular concern is the plankton at the base of the aquatic food chain, which is too small and weak to swim on its own and drifts along helplessly with the ocean currents.

The Ocean Cleanup's recent redesign also sought to address this problem by switching from nets to solid screens. Spokesperson Jan van Ewijk tells us that this will prevent most marine life being caught in the booms, though it is clear that environmentalists will be seeking far more conclusive answers before the time comes to roll out a full-scale system.

"Vertebrates like fish, marine mammals, sea turtles will be able to swim under and around the solid screen," says van Ewijk. "Most plankton is neutrally buoyant and therefore we anticipate the natural currents to guide the plankton under the screen and floating system. However, some macro plankton species like jellyfish are positively buoyant and it is possible we will intercept some of them in front of the barrier, together with the plastic."

When The Ocean Cleanup project goes ahead with its pilot this year, it will work with experts to monitor the planktonic life caught up in its barriers, van Ewijk tells us, along with the risks to larger organisms. He also says that investigating the dangers to marine life is an ongoing effort.

"We are fully committed to do a full Environmental Impact Assessment on our technology when the time is right," van Ewijk says. "At every stage of our project, we actively seek to eliminate or significantly reduce any environmental impact that the cleanup may have. We have recently finished an Environmental Impact Exploration, conducted by an external consulting agency. Based on the collection of potential environmental impacts identified in the Exploration study, we are now embarking on more robust environmental impact studies for which we require specialists' input."

Turning off the tap

A total of 37.7 million pieces of plastic had washed up and spread out over Henderson Island, researchers say Jennifer Lavers

While some scientists and The Ocean Cleanup Project may disagree on how effective these booms will be, one thing that everyone seems to agree on is that the only real answer is to stop this problem at its source. With our plastic production only going up and huge portions of that spilling into the oceans, it seems that any real long-term solutions will involve a good hard look at our how we use plastics.

"The key points here is – and this really needs to be made clear – if all we ever do is clean up, that is literally all we will ever do," says Lavers. "We absolutely must change our behavior, our consumption patterns – the tap must be shut off. The definition of insanity is, literally, doing the same thing over and over and expecting a different outcome. This definition applies here. If all we ever do is clean up, and expect things to change, then … you get the picture."

Lavers points to zero waste communities as real solutions, as does Wilson, who notes the Break Free From Plastic movement made up of 700 NGOs around the world as an example of how people can affect change. Taking steps such as getting rid of low-value plastics like multi-layer packaging and creating massive disincentives on single-use plastics so companies don't default to them would also be positive moves, Wilson says.

"There is already an estimated five trillion pieces of plastic floating in the oceans and more than 1,200 marine species documented to be harmed by all of this plastic," says Lavers. "As hard as it may be, we need to do more as a society to prevent more plastic from entering the oceans. Get creative, make a commitment, and be willing to do whatever you can. Because really, what other option do we have?"

