Oceans have become a plastic soup. But in fact, of all the plastic that enters Earth’s oceans each year, just 1% has been observed floating on the surface. So where is the rest of it?
This “missing” plastic has been a longstanding scientific question. To date, the search has focused on oceanic gyres such as the Great Pacific Garbage Patch, the water column (the part of the ocean between the surface and the sea bed), the bottom of the ocean, and the stomachs of marine wildlife.
But a new research suggests ocean plastic is being transported back onshore and pushed permanently onto land away from the water’s edge, where it often becomes trapped in vegetation.
Of course, plastic has been reported on beaches around the world for decades. But there has been little focus on why and how coastal environments are a sink for marine debris. The findings have big implications for how we tackle ocean plastic.
The hunt for marine pollution
A separate, yet-to-be-published research has found around 90% of marine debris that enters the ocean remains in the “littoral zone” (the area of ocean within 8km of the coast). This new study set out to discover what happens to it.
Collected data on the amount and location of plastic pollution every 100 kilometres around the entire coast of Australia between 2011 and 2016. Debris was recorded at 188 locations along the Australian coastline. Of this, 56% was plastic, followed by glass (17%) and foam (10%).
The debris was a mix of litter from people and deposition from the ocean. The highest concentrations of plastic pollution were found along coastal backshores – areas towards the inland edge of the beach, where the vegetation begins. The further back from the water’s edge we went, the more debris we found.
The amount of marine debris, and where it ends up, is influenced by onshore wave activity and, to a lesser extent, wind activity. Densely populated areas and those where the coast was easily accessible were hotspots for trapped plastics.
Smaller debris is often found near the water’s edge, while larger items such as drink bottles, plastic bags and crisp packets are often found further back from the water, often trapped in vegetation.
The study also found more debris near urban areas where rivers and creeks enter the ocean. It could be that our trash is being trapped by waterways before it gets to the sea, as there are similar patterns in other countries surveyed around the Asia Pacific and beyond.
This pollution kills and maims wildlife when they mistake it for food or get tangled in it. It can damage fragile marine ecosystems by smothering sensitive reefs and transporting invasive species and is potentially a threat to human health if toxins in plastics make their way through the food chain to humans.
It can also become an eyesore, damaging the economy of an area through reduced tourism revenue.
The findings highlight the importance of studying the entire width of coastal areas to better understand how much, and where, debris gets trapped, to inform targeted approaches to managing all this waste.
Plastic pollution can be reduced through local changes such as water refill stations, rubbish bins, incentives and awareness campaigns. It can also be reduced through targeted waste management policies to reduce, reuse and recycle plastics. Container deposit schemes are a particularly effective incentive in reducing marine pollution.
Plastic in the oceans is increasing. It’s clear that waste management strategies on land must accommodate much larger volumes of pollution than previously estimated. But the best way to keep plastic from the ocean and land is to stop putting it in.