Science on alert: the search for lost plastic waste

Dr. Britta Denise Hardesty, a member of The SeaCleaners' International Scientific Advisory Board, lifts the veil on the most common misconceptions about plastic pollution. 

Plastic pollution on coastline

The accumulation of plastic waste in nature is “one of the most widespread and long-lasting recent changes to our planet’s surface” (Barnes et al, 2009). It is also one of the top 5 environmental concerns of our time according to the UN.

Yet we know little about what happens to these plastics.

How do they move from one point to another? Where do they accumulate? How do they enter marine ecosystems? Can they be cleaned up, and if so, how?
Dr. Britta Denise Hardesty lifts the veil on the most common misconceptions about plastic pollution.  

Researcher Dr. Britta Denise Hardesty is a Principal Senior Research Scientist for the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Oceans and Atmosphere.
The SeaCleaners is proud to count Dr Hardesty as a member of its International Scientific Advisory Board.

In October 2022, the BBC headlined The secrets being revealed by ocean garbage patches”, a news piece that echoes the research conducted by the scientist and her team and presented at the 7th International Conference on Marine Debris held in Busan, South Korea, from September 18 to 23, 2022.  

Denise’s point of departure? Solving the unfathomable mystery of “missing plastic,” the relationship between the plastic produced and the trash found in the wild in nature. Every year, about 400 million tons of plastic are produced, which is more or less the weight of the entire human race. 40% are disposable products, including food packaging, or 160 million tons. It is estimated that they are thrown away after one month (Plastic Atlas, 2020). Barely 10% is recycled, 14% is incinerated, about 40% is landfilled, and about 32% ends up in nature, especially in the oceans (id.).  

32% of 160 million, that’s 51.2 million tons… in nature, in rivers, in the sea, we don’t know where. According to various estimates, 9 to 14 million tons are dumped into the oceans every year. Some studies even put the figure at 20 million tons. Where is the delta? Are we underestimating the amount of waste that ends up polluting the marine environment? Are there other explanations? 

Britta Denise Hardesty
Denise Hardesty - Credit : Csiro

A new and more comprehensive model 

This is the investigation that Denise and her team are conducting. And while many questions remain about the “missing plastic,” the good news is that there is now more and more data available to understand where this waste ends up, including a new modeling tool that predicts how much waste will be found on the coast. 

What does this model contribute? It does not only take into account the population density, as previous models did. It also considers the distance of poorly managed and abandoned waste from the nearest river mouth, the distance to the nearest road, the socio-economic status of the area, the frequency of beach visits, the morphology of the beaches, the vegetation cover of the area, and terrestrial geographic data. 

For Dr. Hardesty, there are many misconceptions about the trash we see in the ocean: while in some places we may see it floating and stagnating, in others ocean currents carry it offshore where it accumulates in ocean gyres, the so-called “plastic continents” (such as the “Great Garbage Patch” in the North Pacific). 

The United Nations Environment Programme estimates that there are between 75 and 199 million tons of plastic in the ocean today, but it is impossible to know for sure how much of this plastic ends up in the garbage patches, as much of it remains trapped near the coast.  

Stuck in vegetation or in the coastal zone 

What the new data indicate is that “most of the plastic or the waste that’s lost into the environment doesn’t go to these garbage patches. It doesn’t go out into the middle of the ocean (…)”. While “most of our debris actually ends up trapped in the back shore vegetation on land,” Denise adds that not all trash gets trapped on land, far from it. “If there are hundreds of tonnes of garbage that are making their way into the ocean, more buoyant items can still break through the littoral zone, which extends around 8km (5 miles) from the shore. From there, a combination of wind, current, and waves can break down rubbish and take the pieces thousands of miles from their point of origin.” 

“[For instance] we know that items moved all the way from Japan to the west coast of the United States in under a year after the [2011] tsunami blew large objects like motorcycles and floating docks across the Pacific Ocean in a year, or two years,” she tells the BBC.  

Taking action on land and at sea 

Collecting plastic waste directly from the gyres or from the open ocean is a difficult task. The most effective action is to reduce or eliminate waste upstream, long before it can reach the open ocean. Reducing plastic pollution near the coast and on land, in areas of high concentration and before waste disperses and drifts, ultimately means less pollution entering the ocean. 

At The SeaCleaners, we are closely following Denise’s work, which sheds light on the areas of intervention of our waste cleaning boats: in rivers and streams, along the coasts in the famous littoral zone, near estuaries and the mouths of large rivers, where slicks of pollution in the marine environment will stagnate and remain concentrated for a while. But they also remind us of the crucial importance of cleaning up on land near the coastal zones and rivers, during citizen clean-ups, of prevention and awareness to eliminate waste at the source, and of the drastic reduction of our consumption of single-use plastic.  

These are all battles that we are fighting and will continue to fight tirelessly, supported by our volunteers, our International Scientific Council, our patrons and our partners.