How do we save whales and other marine animals from plastic in the ocean? Our new review shows reducing plastic pollution can prevent the deaths of beloved marine species. Over 700 marine species, including half of the world’s cetaceans (such as whales and dolphins), all of its sea turtles and a third of its seabirds, are known to ingest plastic.
When animals eat plastic, it can block their digestive system, causing a long, slow death from starvation. Sharp pieces of plastic can also pierce the gut wall, causing infection and sometimes death. As little as one piece of ingested plastic can kill an animal.
About eight million tonnes of plastic enters the ocean each year, so solving the problem may seem overwhelming. How do we reduce harm to whales and other marine animals from that much plastic?
Like a hospital overwhelmed with patients, we triage. By identifying the items that are deadly to the most vulnerable species, we can apply solutions that target these most deadly items.
We tested these expert predictions by assessing data from 76 published research papers incorporating 1,328 marine animals (132 cetaceans, 20 seals and sea lions, 515 sea turtles and 658 seabirds) from 80 species.
We examined which items caused the greatest number of deaths in each group, and also the “lethality” of each item (how many deaths per interaction). We found the experts got it right for three of four items.
Flexible plastics, such as plastic sheets, bags and packaging, can cause gut blockage and were responsible for the greatest number of deaths over all animal groups. These film plastics caused the most deaths in cetaceans and sea turtles. Fishing debris, such as nets, lines and tackle, caused fatalities in larger animals, particularly seals and sea lions.
Turtles and whales that eat debris can have difficulty swimming, which may increase the risk of being struck by ships or boats. In contrast, seals and sea lions don’t eat much plastic, but can die from eating fishing debris.
Balloons, ropes and rubber, meanwhile, were deadly for smaller fauna. And hard plastics caused the most deaths among seabirds. Rubber, fishing debris, metal and latex (including balloons) were the most lethal for birds, with the highest chance of causing death per recorded ingestion.
The most cost-efficient way to reduce marine megafauna deaths from plastic ingestion is to target the most lethal items and prioritise their reduction in the environment.
Targeting big plastic items is also smart, as they can break down into smaller pieces. Small debris fragments such as microplastics and fibres are a lower management priority, as they cause significantly fewer deaths to megafauna and are more difficult to manage.
Flexible film-like plastics, including plastic bags and packaging, rank among the ten most common items in marine debris surveys globally. Plastic bag bans and fees for bags have already been shown to reduce bags littered into the environment. Improving local disposal and engineering solutions to enable recycling and improve the life span of plastics may also help reduce littering.
Lost fishing gear is particularly lethal. Fisheries have high gear loss rates: 5.7% of all nets and 29% of all lines are lost annually in commercial fisheries. The introduction of minimum standards of loss-resistant or higher quality gear can reduce loss.
incentivising gear repairs and port disposal of damaged nets
penalising or prohibiting high-risk fishing activities where snags or gear loss are likely
and enforcing penalties associated with dumping.
Outreach and education to recreational fishers to highlight the harmful effects of fishing gear could also have benefit.
Balloons, latex and rubber are rare in the marine environment, but are disproportionately lethal, particularly to sea turtles and seabirds. Preventing intentional balloon releases and accidental release during events and celebrations would require legislation and a shift in public will.
The Pacific Ocean is the deepest, largest ocean on Earth, covering about a third of the globe’s surface. An ocean that vast may seem invincible. Yet across its reach – from Antarctica in the south to the Arctic in the north, and from Asia to Australia to the Americas – the Pacific Ocean’s delicate ecology is under threat.
In most cases, human activity is to blame. We have systematically pillaged the Pacific of fish. We have used it as a rubbish tip – garbage has been found even in the deepest point on Earth, in the Mariana Trench 11,000 metres below sea level.
And as we pump carbon dioxide into the atmosphere, the Pacific, like other oceans, is becoming more acidic. It means fish are losing their sense of sight and smell, and sea organisms are struggling to build their shells.
Oceans produce most of the oxygen we breathe. They regulate the weather, provide food, and give an income to millions of people. They are places of fun and recreation, solace and spiritual connection. So, healthy, vibrant oceans benefit us all. And by better understanding the threats to the precious Pacific, we can start the long road to protecting it.
The series opens with five profiles delving into ancient Indian Ocean trade networks, Pacific plastic pollution, Arctic light and life, Atlantic fisheries and the Southern Ocean’s impact on global climate. It’s brought to you by The Conversation’s international network.
The ocean plastic scourge
The problem of ocean plastic was scientifically recognised in the 1960s after two scientists saw albatross carcasses littering the beaches of the northwest Hawaiian Islands in the northern Pacific. Almost three in four albatross chicks, who died before they could fledge, had plastic in their stomachs.
Now, plastic debris is found in all major marine habitats around the world, in sizes ranging from nanometers to meters. A small portion of this accumulates into giant floating “garbage patches”, and the Pacific Ocean is famously home to the largest of them all.
Plastic debris in the oceans presents innumerable hazards for marine life. Animals can get tangled in debris such as discarded fishing nets, causing them to be injured or drown.
Some organisms, such as microscopic algae and invertebrates, can also hitch a ride on floating debris, travelling large distances across the oceans. This means they can be dispersed out of their natural range, and can colonise other regions as invasive species.
And of course, wildlife can be badly harmed by ingesting debris, such as microplastics less than five millimetres in size. This plastic can obstruct an animal’s mouth or accumulate in its stomach. Often, the animal dies a slow, painful death.
Seabirds, in particular, often mistake floating plastics for food. A 2019 study found there was a 20% chance seabirds would die after ingesting a single item, rising to 100% after consuming 93 items.
And since floating plastics in the open ocean are transported mainly by ocean surface currents and winds, plastic debris accumulates on island coastlines along their path. Kamilo Beach, on the south-eastern tip of Hawaii’s Big Island, is considered one of the world’s worst for plastic pollution. Up to 20 tonnes of debris wash onto the beach each year.
Similarly, on uninhabited Henderson Island, part of the Pitcairn Island chain in the south Pacific, 18 tonnes of plastic have accumulated on a beach just 2.5km long. Several thousand pieces of plastic wash up each day.
Subtropical garbage patches
Plastic waste can have different fates in the ocean: some sink, some wash up on beaches and some float on the ocean surface, transported by currents, wind and waves.
Around 1% of plastic waste accumulates in five subtropical “garbage patches” in the open ocean. They’re formed as a result of ocean circulation, driven by the changing wind fields and the Earth’s rotation.
There are two subtropical garbage patches in the Pacific: one in the northern and one in the southern hemisphere.
The northern accumulation region is separated into an eastern patch between California and Hawaii, and a western patch, which extends eastwards from Japan.
Our ocean garbage shame
First discovered by Captain Charles Moore in the early 2000s, the eastern patch is better known as the Great Pacific Garbage Patch because it’s the largest by both size (around 1.6 million square kilometers) and amount of plastic. By weight, this garbage patch can hold more than 100 kilograms per square kilometre.
The garbage patch in the southern Pacific is located off Valparaiso, Chile, extending to the west. It has lower concentrations compared to its giant counterpart in the northeast.
Discarded fishing nets make up around 45% of the total plastic weight in the Great Pacific Garbage Patch. Waste from the 2011 Japan tsunami is also a major contributor, making up an estimated 20% of the patch.
Each year, up to 15 million tonnes of plastic waste are estimated to make their way into the ocean from coastlines and rivers. This amount is expected to double by 2025 as plastic production continues to increase.
We must act urgently to stem the flow. This includes developing plans to collect and remove the plastics and, vitally, stop producing so much in the first place.
Fisheries on the verge of collapse
As the largest and deepest sea on Earth, the Pacific supports some of the world’s biggest fisheries. For thousands of years, people have relied on these fisheries for their food and livelihoods.
But, around the world, including in the Pacific, fishing operations are depleting fish populations faster than they can recover. This overfishing is considered one of the most serious threats to the world’s oceans.
Humans take about 80 million tonnes of wildlife from the sea each year. In 2019, the world’s leading scientists said of all threats to marine biodiversity over the past 50 years, fishing has caused the most harm. They said 33% of fish species were overexploited, 60% were being fished to the maximum level, and just 7% were underfished.
The decline in fish populations is not just a problem for humans. Fish play an important role in marine ecosystems and are a crucial link in the ocean’s complex food webs.
Not plenty of fish in the sea
Overfishing happens when humans extract fish resources beyond the maximum level, known as the “maximum sustainable yield”. Fishing beyond this causes global fish stocks to decline, disrupts food chains, degrades habitats, and creates food scarcity for humans.
The Pacific Ocean is home to huge tuna fisheries, which provide almost 65% of the global tuna catch each year. But the long-term survival of many tuna populations is at risk.
For example, a study released in 2013 found numbers of bluefin tuna – a prized fish used to make sushi – had declined by more than 96% in the Northern Pacific Ocean.
Developing countries, including Indonesia and China, are major overfishers, but so too are developing nations.
Along Canada’s west coast, Pacific salmon populations have declined rapidly since the early 1990s, partly due to overfishing. And Japan was recently heavily criticised for a proposal to increase quotas on Pacific bluefin tuna, a species reportedly at just 4.5% of its historic population size.
Experts say overfishing is also a problem in Australia. For example, research in 2018 showed large fish species were rapidly declining around the nation due to excessive fishing pressure. In areas open to fishing, exploited populations fell by an average of 33% in the decade to 2015.
So what’s driving overfishing?
There are many reasons why overfishing occurs and why it is goes unchecked. The evidence points to:
Let’s take Indonesia as an example. Indonesia lies between the Pacific and Indian oceans and is the world’s third-biggest producer of wild-capture ﬁsh after China and Peru. Some 60% of the catch is made by small-scale ﬁshers. Many hail from poor coastal communities.
Overfishing was first reported in Indonesia in the 1970s. It prompted a presidential decree in 1980, banning trawling off the islands of Java and Sumatra. But overfishing continued into the 1990s, and it persists today. Target species include reef fishes, lobster, prawn, crab, and squid.
Indonesia’s experience shows how there is no easy fix to the overfishing problem. In 2017, the Indonesian government issued a decree that was supposed to keep fishing to a sustainable level – 12.5 million tonnes per year. Yet, in may places, the practice continued – largely because the rules were not clear and local enforcement was inadequate.
Implementation was complicated by the fact that almost all Indonesia’s smaller fishing boats come under the control of provincial governments. This reveals the need for better cooperation between levels of government in cracking down on overfishing.
What else can we do?
To prevent overfishing, governments should address the issue of poverty and poor education in small fishing communities. This may involve finding them a new source of income. For example in the town of Oslob in the Philippines, former fishermen and women have turned to tourism – feeding whale sharks tiny amounts of krill to draw them closer to shore so tourists can snorkel or dive with them.
Tackling overfishing in the Pacific will also require cooperation among nations to monitor fishing practices and enforce the rules.
And the world’s network of marine protected areas should be expanded and strengthened to conserve marine life. Currently, less than 3% of the world’s oceans are highly protected “no take” zones. In Australia, many marine reserves are small and located in areas of little value to commercial fishers.
The collapse of fisheries around the world shows just how vulnerable our marine life is. It’s clear that humans are exploiting the oceans beyond sustainable levels. Billions of people rely on seafood for protein and for their livelihoods. But by allowing overfishing to continue, we harm not just the oceans, but ourselves.
The tropical and subtropical waters of the Pacific Ocean are home to more than 75% of the world’s coral reefs. These include the Great Barrier Reef and more remote reefs in the Coral Triangle, such as those in Indonesia and Papua New Guinea.
Coral reefs are bearing the brunt of climate change. We hear a lot about how coral bleaching is damaging coral ecosystems. But another insidious process, ocean acidification, is also threatening reef survival.
Ocean acidification particularly affects shallow waters, and the subarctic Pacific region is particularly vulnerable.
Coral reefs cover less than 0.5% of Earth’s surface, but house an estimated 25% of all marine species. Due to ocean acidification and other threats, these incredibly diverse “underwater rainforests” are among the most threatened ecosystems on the planet.
A chemical reaction
Ocean acidification involves a decrease in the pH of seawater as it absorbs carbon dioxide (CO₂) from the atmosphere.
Each year, humans emit 35 billion tonnes of CO₂ through activities such as burning of fossil fuels and deforestation.
Oceans absorb up to 30% of atmospheric CO₂, setting off a chemical reaction in which concentrations of carbonate ions fall, and hydrogen ion concentrations increase. That change makes the seawater more acidic.
Ocean acidification is also a problem for the fishes. Many studies have revealed elevated CO₂ can disrupt their sense of smell, vision and hearing. It can also impair survival traits, such as a fish’s ability to learn, avoid predators, and select suitable habitat.
However, ocean acidification does not affect all marine species in the same way, and the effects can vary over the organism’s lifetime. So, more research to predict the future winners and losers is crucial.
This can be done by identifying inherited traits that can increase an organism’s survival and reproductive success under more acidic conditions. Winner populations may start to adapt, while loser populations should be targets for conservation and management.
One such winner may be the epaulette shark, a shallow water reef species endemic to the Great Barrier Reef. Research suggests simulated ocean acidification conditions do not impact early growth, development, and survival of embryos and neonates, nor do they affect foraging behaviours or metabolic performance of adults.
But ocean acidification is also likely to create losers on the Great Barrier Reef. For example, researchers studying the orange clownfish – a species made famous by Disney’s animated Nemo character – found they suffered multiple sensory impairments under simulated ocean acidification conditions. These ranged from difficulties smelling and hearing their way home, to distinguishing friend from foe.
It’s not too late
More than half a billion people depend on coral reefs for food, income, and protection from storms and coastal erosion. Reefs provide jobs – such as in tourism and fishing – and places for recreation. Globally, coral reefs represent an industry worth US$11.9 trillion per year. And importantly, they’re a place of deep cultural and spiritual connection for Indigenous people around the world.
Cutting greenhouse gas emissions must become a global mission. COVID-19 has slowed our movements across the planet, showing it’s possible to radically slash our production of CO₂. If the world meets the most ambitious goals of the Paris Agreement and keeps global temperature increases below 1.5℃, the Pacific will experience far less severe decreases in oceanic pH.
We will, however, have to curb emissions by a lot more – 45% over the next decade – to keep global warming below 1.5℃. This would give some hope that coral reefs in the Pacific, and worldwide, are not completely lost.
Clearly, the decisions we make today will affect what our oceans look like tomorrow.
In my career as a marine biologist, I’ve been fortunate enough to visit some of the most remote islands in the world. These beautiful places continue to remind me why I have this job in the first place, but they also bring home the pervasive influence of human societies. Uninhabited bird colonies on the Canadian West Coast, remote tropical Japanese islands, and tiny bits of land in South East Asia all have one thing in common: plastic waste on the beach.
When at home in Sweden, I regularly swim and sail in the Baltic Sea. But agricultural fertilisers and other types of pollution have created dead zones where fish either leave or suffocate. Meanwhile, offshore fisheries and aquaculture farms in many parts of the world overharvest and pollute the water. We know what proper management of these activities could look like, but political will has so far not been equal to the challenge.
That may be about to change. A recent agreement between 14 heads of state – together representing 40% of the world’s coastline – promised to end overfishing, restore fish stocks and halt the flow of plastic pollution into the ocean within a decade.
Pollution, plastics and unsustainable seafood may look like isolated problems, but they influence each other. As nutrients run off farmland and into the sea, they affect the conditions fish need to thrive. Pollution makes our seafood less healthy and overfishing is pushing some fish stocks beyond their capacity to renew themselves.
It’s in everyone’s interests to protect the ocean. Clean seas would be more profitable and research suggests that better managed fisheries could generate six times more food than they do currently. The exclusive economic zones of coastal states would be more productive if every country agreed to protect the high seas. And sailing in the Baltic Sea would be much nicer if the boat didn’t have to plough a thick, green sludge.
So how can the world make progress – and what’s holding us back?
As part of the recent agreement between 14 heads of state, the participating countries – Australia, Canada, Chile, Fiji, Ghana, Indonesia, Jamaica, Japan, Kenya, Mexico, Namibia, Norway, Palau and Portugal – committed to a number of goals within their national waters, including investment in zero-emission shipping, eliminating waste and ensuring fisheries are sustainable. The aim is to ensure all activity within these exclusive economic zones is sustainable by 2025.
The countries agreed to fast-track their plan for action, rather than work through the UN. Their combined national waters roughly equal the size of Africa. They each have clear stakes in the continued functioning of ocean ecosystems and economies, so this pragmatic approach makes sense. That’s a sentiment that businesses could no doubt respect. After all, there are no economic opportunities in a dead ocean.
The agreement is an encouraging message from political leaders, and these states can leverage vast sums of money and resources to effect change. But the ocean is home to a dozen global industries, and around 50,000 vessels traverse it at any one time. Clearly, we need more than governments to deliver on this ambitious agenda.
My scientific colleagues and I have been developing a global coalition of businesses concerned with sustainable seafood. Our strategy is to find “keystone actors” within the private sector – companies with a disproportionate ability to influence change due to their size and strength.
The seafood industry is vast, and includes some of the largest companies in the world – from entire fisheries, to aquaculture farms and feed processors. After four years of working together, change within the participating companies is accelerating. For example, Nissui, the world’s second-largest seafood company, has evaluated their entire production portfolio for sustainability challenges.
Collaboration between scientists and businesses is vital to delivering commitments made by governments. Scientists can help define the problems, and business can develop, pilot and scale solutions. For instance, we’re developing software that can automatically detect which species of fish are caught on vessels, to radically improve the transparency of seafood production.
The ocean has been a source of inspiration, imagination and adventure since the beginning of time. It has fed us and generated livelihoods for billions. Politicians have stood serenely on the sidelines for some time now, content to be passive observers of deteriorating ecosystems. But the era of passive observation may finally be coming to an end.
Freshwater ecosystems are a priority for environmental scientists because they affect the health of animals and plants on land too – as well as people. They provide food, water, transport and flood control. Freshwater ecosystems also keep nutrients moving among organisms and support diverse forms of life.
Freshwater systems make a big difference to the quality of life in any human society. But they are under great pressure. Freshwater biodiversity is declining faster than terrestrial biodiversity.
One of the biggest stresses on freshwater ecosystems is the presence of plastics. Some microplastics – tiny pieces of plastic that have broken down from bigger pieces – get into water from various sources. Some are introduced from industrial sources like cosmetics, toothpaste and shaving cream. Another major source is dumping of plastic waste like bags and bottles.
In Nigeria, an important source is the plastic sachets that contain drinking water. Over 60 million of these are consumed in a day.
Ultimately all these types of plastic waste find their way to the aquatic environment. There they stay in the water column, settle on river beds or are ingested by aquatic animals.
My research group set out to assess the load and chemical nature of microplastics in two important rivers and Gulf of Guinea tributaries in Nigeria. We looked for the presence of microplastics in aquatic insects since they often dominate aquatic animal life. Most also spend their adult stage in the terrestrial environment, once they emerge from their larvae. We found that microplastics were present in large quantities in the insect larvae. The insects are part of a food chain and could transfer the harmful effects of microplastics throughout the chain.
This further reinforces the urgent need for Nigeria to go ahead with measures to reduce the use of plastic bags and single-use plastics.
The research findings
We used three of the rivers’ aquatic insect species as bio-indicators and found that all three had ingested microplastics from the two rivers. The ingested microplastics include styrene-ethylene-butylene-styrene, acrylonitrile butadiene styrene, chlorinated polyethylene, polypropylene, and polyester. The quantity of microplastics ingested by the insects was fairly high, especially in the Chironomus sp. which is a riverbed dweller recorded in the Ogun River.
The diversity of plastic polymers recorded in these insects suggests a wide range of applications of plastics in Nigeria.
The three insect species spend their larval stages in the water and later migrate to land in the adult phase. The concern is that the insect larvae could serve as a link for microplastics’ transfer to higher trophic levels in the aquatic environment. Also, the adults serve in the same capacity in the terrestrial environment. A trophic level is the group of organisms within an ecosystem which occupy the same level in a food chain.
Dragonfly larvae in the water are eaten by fish, salamanders, turtles, birds and beetles. Adult dragonflies on land are also eaten by birds and other insects.
Through feeding, the transfer of microplastics in the environment could go as far as people – who caused the plastic pollution in the first place.
Evidence suggests that microplastics reduce the physiological fitness of animals. This comes through decreased food consumption, weight loss, decreased growth rate, energy depletion and susceptibility to other harmful substances. Human health could similarly be at risk on account of microplastic ingestion.
A ban on plastic bags would curb the plastic pollution in Nigeria. There are alternatives to the use of plastic bags, for instance, bags made from banana stalks, coconut, palm leaf, cassava flour and chicken feathers. Unlike plastic bags, which could persist in the environments for over a century, bags made from these organic materials decompose readily in a manner that does not pose a health risk to the environment.
For a long while, the call to mitigate plastic pollution was not heeded in Nigeria. Recently, the House of Representatives passed a bill banning plastic bags. But this is yet to be implemented as the president has not assented to it.
A study in the European Union indicates that a ban on single-use plastics could reduce marine plastic pollution by about 5.5%.
It is about time Nigeria treated plastic pollution as a national emergency, considering its implications for human health and the ecological integrity of aquatic ecosystems. An approach that puts people at the centre of the issue has been suggested as one way to convince local communities to preserve the integrity of the environment.
Perhaps this approach could help restore plastic-laden aquatic ecosystems and preserve the pristine ones.
Addressing plastic packaging is key to reversing these negative trends. It accounts for 42% of all non-fibre plastics produced.
But the plastics industry is pushing back. Industry representatives claim efforts to regulate plastic packaging will have negative environmental consequences because plastic is a lightweight material with a lower carbon footprint than alternatives like glass, paper and metal.
These claims are based on what’s known as life-cycle assessment (LCA). It’s a tool used to measure and compare the environmental impact of materials throughout their life, from extraction to disposal.
While independent LCA practitioners may adopt rigorous processes, the method is vulnerable to misuse. According to European waste management consultancy Eunomia, it is limited by the questions it seeks to answer:
Ask inappropriate, misleading, narrow or uninformed questions and the process will only provide answers in that vein.
Industry-commissioned life-cycle assessments often frame single-use plastic packaging positively. These claim plastic’s light weight offsets its harmful impacts on people, wildlife and ecosystems. Some studies are even used to justify the continued expansion of plastics production.
But plastic can come out looking good when certain important factors are overlooked. In theory, LCA considers a product’s whole-of-life environmental impact. In practice, the scope varies as practitioners select system boundaries at their discretion.
Zero Waste Europe has highlighted that life-cycle assessment for food packaging often omits important considerations. These include the potential toxicity of different materials, or the impact of leakage into the environment. Excluding factors like this gives plastics an unjustified advantage.
Researchers have acknowledged the method’s critical failure to account for marine pollution. This is now a priority for the research community, but not the plastics industry.
Even questionable LCA studies carry a veneer of authority in the public domain. The packaging industry capitalises on this to distract, delay and derail progressive plastics legislation. Rebutting industry studies that promote the environmental superiority of plastics is difficult because commissioning a robust LCA is costly and time-consuming.
LCA appeals to policymakers aspiring to develop evidence-based packaging policy. But if the limitations are not properly acknowledged or understood, policy can reinforce inaccurate industry narratives.
The report dedicates an entire chapter to LCA. It includes case studies that do not actually take a full life-cycle approach from extraction to disposal. It concedes only on the last page that LCA does not account for the environmental, economic or health impacts of plastics that leak into the environment.
The report also erroneously suggests LCA is “an alternative approach” to the zero-waste hierarchy. In fact, the two tools work best together.
The zero-waste hierarchy prioritises strategies to prevent, reduce and reuse packaging. That’s based on the presumption that these approaches have lower life-cycle impacts than recycling and landfilling.
One of LCA’s limitations is that practitioners tend to compare materials already available on the predominantly single-use packaging market. However, an LCA guided by the waste hierarchy would include zero-packaging or reusable packaging systems in the mix. Such an assessment would contribute to sustainable packaging policy.
A reduction of plastic production — through elimination, the expansion of consumer reuse options, or new delivery models — is the most attractive solution from environmental, economic and social perspectives.
Policymakers should take life-cycle assessment beyond its industry-imposed straitjacket and allow it to inform zero-packaging and reusable packaging system design. Doing so could help New Zealand reduce plastic pollution, negative health impacts and greenhouse gas emissions.
But just how bad is the problem? Our new research provides the first global estimate of microplastics on the seafloor — our research suggests there’s a staggering 8-14 million tonnes of it.
This is up to 35 times more than the estimated weight of plastic pollution on the ocean’s surface.
What’s more, plastic production and pollution is expected to increase in coming years, despite increased media, government and scientific attention on how plastic pollution can harm marine ecosystems, wildlife and human health.
These findings are yet another wake-up call. When the plastic we use in our daily lives reaches even the deepest oceans, it’s more urgent than ever to find ways to clean up our mess before it reaches the ocean, or to stop making so much of it in the first place.
Breaking down larger plastic
Our estimate of microplastics on the seafloor is huge, but it’s still a fraction of the amount of plastic dumped into the ocean. Between 4-8 million tonnes of plastic are thought to enter the sea each and every year.
Most of the plastic dumped into the ocean likely ends up on the coasts, not floating around the ocean’s surface or on the seafloor. In fact, three-quarters of the rubbish found along Australia’s coastlines is plastics.
The larger pieces of plastic that stay in the ocean can deteriorate and break down from weathering and mechanical forces, such as ocean waves. Eventually, this material turns into microplastics, pieces smaller than 5 millimetres in diameter.
Their tiny size means they can be eaten by a variety of marine wildlife, from plankton to crustaceans and fish. And when microplastics enter the marine food web at low levels, it can move up the food chain as bigger species eat smaller ones.
But the problem isn’t as well documented for microplastics on the seafloor. While plastics, including microplastics, have been found in deep-sea sediments in all ocean basins across the world, samples have been small and scarce. This is where our research comes in.
Collecting samples in the Great Australian Bight
We collected samples using a robotic submarine in a range of sea depths, from 1,655 to 3,062 metres, in the Great Australian Bight, up to 380 kilometres offshore from South Australia. The submarine scooped up 51 samples of sand and sediment from the seafloor and we analysed them in a laboratory.
We dried the sediment samples, and found between zero and 13.6 plastic particles per gram. This is up to 25 times more microplastics than previous deep-sea studies. And it’s much higher than studies in other regions, including in the Arctic and Indian Oceans.
While our study looked at one general area, we can scale up to calculate a global estimate of microplastics on the seafloor.
Using the estimated size of the entire ocean — 361,132,000 square kilometres — and the average number and size of particles in our sediment samples, we determined the total, global weight as between 8.4 and 14.4 million tonnes. This range takes into account the possible weights of individual microplastics.
How did the plastic get there?
It’s important to note that since our location was remote, far from any urban population centre, this is a conservative estimate. Yet, we were surprised at just how high the microplastic loads were there.
Few studies have conclusively identified how microplastics travel to their ultimate fate.
Larger pieces of plastic that get broken down to smaller pieces can sink to the seafloor, and ocean currents and the natural movement of sediment along continental shelves can transport them widely.
But not all plastic sinks. A 2016 study suggests interaction with marine organisms is another possible transport method.
Scientists in the US have shown microbial communities, such as bacteria, can inhabit this marine “plastisphere” — a term for the ecosystems that live in plastic environments. The microbes weigh the plastic down so it no longer floats. We also know mussels and other invertebrates may colonise floating plastics, adding weight to make them sink.
For example, in a previous study we found cigarette butts, plastic fragments, bottlecaps and food wrappers are common on land, though rare on the seabed. Meanwhile, we found entangling items such fishing line, ropes and plastic bags are common on the seafloor.
Interestingly, in our new study we also found the number of plastic fragments on the seafloor was generally higher in areas where there was floating rubbish on the ocean’s surface. This suggests surface “hotspots” may be reflected below.
It’s not clear why just yet, but it could be because of the geology and physical features of the seabed, or because local currents, winds and waves result in accumulating zones on the ocean’s surface and the seabed nearby.
Stop using so much plastic
Knowing how much plastic sinks to the ocean floor is an important addition to our understanding of the plastic pollution crisis. But stemming the rising tide of plastic pollution starts with individuals, communities and governments – we all have a role to play.
Reusing, refusing and recycling are good places to start. Seek alternatives and support programs, such as Clean Up Australia Day, to stop plastic waste from entering our environment in the first place, ensuring it doesn’t then become embedded in our precious oceans.
It seems you cannot go a day without reading about the impact of plastic in our oceans, and for good reason. The equivalent of a garbage truck of plastic waste enters the sea every minute, and this increases every day. If we do nothing, by 2040 the amount of plastic entering the ocean will triple from 13 million tonnes this year, to 29 million tonnes in 2040. That is 50kg of waste plastic entering the ocean for every metre of coastline.
Add to that almost all the plastic that has entered the ocean is still there since it takes centuries to break down. It is either buried or broken down into smaller pieces and potentially passes up the food chain creating further problems.
Despite this, plastic has also been a saviour. During the COVID-19 pandemic plastic used in face masks, testing kits, screens and to protecting food has enabled countries to come out of lockdown during and support social distancing. We still need to use these items until sustainable and “COVID safe” alternatives are available. But we also need to look to the future to reduce our dependence on plastic and its impact on the environment. With plastic in the ocean being a global problem, we need global agreements and policies to reverse the plastic tide.
Environment ministers of the G20 group of the world’s most economically powerful countries and regions met on September 16 to discuss their immediate challenges, with marine plastic pollution a top priority. A key item for discussion was “safeguarding the planet by fostering collective efforts to protect our global commons”. This means working out how we can continue to use the planet’s resources sustainably without harming the environment.
A global analysis of plastics policies over the past two decades found that typical reactions to marine plastic litter were bans or taxes on individual or groups of plastic items within single countries. So far, 43 countries have introduced a ban, tax or levy on plastic bags. Other plastic packaging or single-use plastic products were banned in at least 25 countries, representing a population of almost 2 billion people in 2018.
But plastic waste doesn’t respect land or ocean borders, with mismanaged plastic waste easily migrating from country to country when leaked into the environment. Policies also need to consider the entire plastics life cycle to stand a chance of being effective. For example, the inclusion of easier to recycle plastics in consumer products sounds positive, but their actual recycling rate depends on effective sorting and collection of plastic waste, and appropriate infrastructure being in place.
Ultimately, a joined up but adaptable set of rules and guidelines are needed so all plastic producers and users can prevent its leakage across all stages of the plastics life cycle.
The G20 has sought to lead action on marine plastic litter through a 2017 Action Plan on Marine Litter which set out areas of concern and possible policy interventions, and through connections to initiatives such as the UN Environment Programme’s Global Partnership on Marine Litter and most recently the Osaka Blue Ocean Vision. The Osaka vision was agreed under the Japanese G20 presidency in 2019 and commits countries to “reduce additional pollution by marine plastic litter to zero by 2050”. Although an agreement led by the G20, it now has the support of 86 countries.
But even with these agreements in place, plastic entering the ocean will still only reduce by 7% by 2040. We need ambitious new agreements as current and emerging policies do not meet the scale of the challenge.
A consensus is forming that the G20 and other global leaders must focus on a systemic change of the plastics economy. This includes focusing on “designing out” plastics, promoting technical and business innovation, immediately scaling up actions known to reduce marine plastic litter, and transitioning to a circular economy in which materials are fully recovered and reused. These actions have the potential to contribute to the G20’s vision of net-zero plastics entering the ocean by 2050, but only if ambitious actions are taken now.
After 16 weeks in an industrial compost heap, we unearthed blue and white balloons and found them totally unscathed. The knots we spent hours painstakingly tying by hand more than four months ago were still attached, and sparkly blue balloons still glinted in the sun.
These balloons originally came from packages that advertised them as “100% biodegradable”, with the manufacturers assuring they were made of “100% natural latex rubber”. The implication is that these balloons would have no trouble breaking down in the environment.
This appeals to eco-conscious consumers, but really just fuels corporate greenwashing — unsubstantiated claims of environmentally friendly and safe products.
Holding perfectly intact balloons in our hands after four months in industrial compost, we had cause to question these claims, and ran experiments.
What’s the problem?
This problem is two-fold. First, balloons are additional plastic waste in the environment. They are lightweight and can travel on air currents far from the point of release. For example, one 2005 study found a balloon travelled more than 200 kilometres.
Even more chemicals have to be used to make the additives “stick” to the latex and to stick to each other, enabling them to work in tandem to create a product we expect to use for about 24 hours. So, the balloons can’t be “100% natural rubber latex”.
And yet, despite substantial evidence of harm and the presence of these chemicals, balloon littering persists. Balloon releases are common, with only some regional regulations in place, such as in New South Wales and the Sunshine Coast.
Lying for decades
While some factions of the balloon industry denounce balloon releases, these claims are only recent.
For decades, the industry relied on one industry-funded study from 1989 which claimed that after six short weeks, balloons degraded “at about the same rate as oak tree leaves” and there was no way balloons were a threat to wildlife.
That study was not peer-reviewed, its methods are unclear and not repeatable, and the results are based on only six balloons.
Because balloons are frequently reported to be at sea, ingested by wild animals and washed up on beaches, it’s clear they’re not breaking down in only six weeks. Anecdotal studies have tested this to varying degrees, confirming balloons don’t break down.
Only one peer-reviewed scientific study has quantified balloon degradation, and that also occurred in 1989 — the same year as the industry study. They tested elasticity for up to one year, which means the balloons were intact for that whole time.
We wanted to know: has anything changed since 1989? And why aren’t there more studies testing balloon degradation, given the passion behind the balloon issue?
So, we set out to quantify exactly how long latex balloons would take to break down. And we asked if balloons degraded differently in different parts of the environment.
Our experiment tested their claims
Industrial composting standards require that the material completely disintegrates after 12 weeks and that the product is not distinguishable from the surrounding soil.
We designed an experiment: after exposing balloons to six hours of sunlight (to simulate typical use, for example, at an outdoor party), we put blue and white balloons in industrial compost, and in saltwater and freshwater tanks.
We allowed for aeration to simulate natural conditions, but otherwise, we left the balloons alone. Every two weeks, we randomly removed 40 balloons from each treatment. We photographed them to document degradation. Then we tested them.
Were the balloons still stretchy? We tested this in the University of Tasmania engineering lab to determine tensile (resistence) strength. We found that in water tanks, the balloons became less stretchy, losing around 75% of their tensile strength. But if they had been composted, balloons retained their stretchiness.
Were the balloons still composed of the same things they started with? We tested this by taking spectral measurements of the balloons’ surface. The balloons showed signs they were exposed to ultra violet light in the water tanks, but not in the compost. This means their chemical composition changed in water, but only slightly.
Finally, and most importantly, did the balloons lose mass?
After 16 weeks, the balloons were still recognisably balloons, though they behaved a little differently in compost, water and saltwater. Some balloons lost 1–2% mass, and some balloons in freshwater gained mass, likely due to osmotic absorption of water.
What can we do?
It’s clear latex balloons don’t meaningfully degrade in 16 weeks and will continue to pose a threat to wildlife. So what can we do as consumers? We offer these tips:
do not release balloons outdoors
do not use helium-filled balloons outdoors (this prevents accidental release, and saves helium), which is a critically limited resource
if you use balloons, deflate and bin them after use
During a visit to a bookstore a few weeks ago, we couldn’t help but stare at a display unit featuring no fewer than ten books telling you how to rid plastics from your daily life. We’re bombarded by information on the topic of marine litter and plastic pollution, but how much do we really know about the problem?
Think about other planetary challenges, like climate change or ozone layer depletion. Mature areas of research have developed around them, allowing scientists to identify where the gases that cause these problems come from, and how much reaches the atmosphere each year.
But when it comes to plastic pollution, we know close to nothing about how and where plastic waste is generated, managed, treated and disposed of, especially in low and middle income countries. As a result, we’re struggling to limit the amount of litter accumulating in the environment.
Our research published in Science involved a herculean effort to spot, track and model the current and future flows of plastics into the world’s land and waterbodies. We found that plastic entering the marine environment is set to double by 2040 and, unless the world acts, more than 1.3 billion tonnes of plastic waste will be dumped on land and in waterbodies.
By identifying the ways in which this litter is produced and distributed, we’ve also discovered how best to reduce the plastic deluge. In the process, we found the unsung heroes on the frontline fighting the pollution crisis who could be the world’s best hope of stemming the tide.
The world’s plastic problem in numbers
We developed a model called Plastic-to-Ocean (P₂O) which combines years of accumulated knowledge on global flows of plastic. It compares our current production, use and management of waste with what is projected in the future.
Do you burn your waste in the garden or in the street? Do you drop it into the river? If you answered no to both of these questions then you are possibly one of the 5.5 billion people whose waste gets collected. If you were among the remaining two billion, what would you do with your uncollected waste? Would you make use of a nearby stream, cliff edge, or perhaps squirrel the odd bag in the woods after dusk?
More often than not, uncollected plastic waste is simply set on fire as a cost-free and effective method of disposal. Our model suggests that cumulatively, more than 2.2 billion tonnes of plastic will be open burned by 2040, far more than the 850 million tonnes that’s anticipated to be dumped on land and the 480 million tonnes in rivers and seas.
Having tracked the sources of plastic items through the supply chain and their fate in the environment, we explored what might help reduce aquatic pollution. We found that the single most effective intervention is to provide a service for the two billion people who currently don’t have their waste collected.
But, of the nine interventions we tested, none solved the problem on their own. Only an integrated approach that in addition to increasing collection coverage includes interventions such as reducing demand for single-use and unrecyclable plastic and improving the business case for mechanical recycling, could be successful. For the countries suffering most from plastic pollution, this knowledge could offer a way forward.
But even in our best-case scenario, in which the world takes the kind of concerted and immediate action proposed in our study, approximately 710 million tonnes of plastic waste will be released into the environment by 2040. That may sound a lot, but it would mean an 80% reduction in the levels of plastic pollution compared to what will happen with no action over the next two decades.
Our work also cast light on the contributions of 11 million waste pickers in low and middle-income countries. These informal workers collect waste items, including plastics, for recycling, to secure a livelihood for day-to-day survival. The model estimates that they may be responsible for 58% of all plastic waste collected for recycling worldwide – more than the combined formal collection services achieve throughout all the high-income countries put together.
Without this informal waste collection sector, the mass of plastic entering rivers and the ocean would be considerably greater. Their efforts should be integrated into municipal waste management plans, not only to recognise their tremendous contribution but to improve the appalling safety standards that they currently endure.
Establishing a comprehensive baseline estimate of sources, stocks and flows of plastic pollution, and then projecting into the future, has been an immense task. When it comes to solid waste, the availability, accuracy and international compatibility of data is notoriously insufficient.
Plastic items occur throughout the world in tens of thousands of shapes, sizes, polymer types and additive combinations. There are also considerable differences in cultural attitudes towards the way waste is managed, how plastic products are consumed, and the types of infrastructure and equipment used to manage it when it becomes waste.
Our modelling effort was a delicate and tedious exercise of simplifying and generalising this complexity. To understand how reliable, accurate, and precise our findings are likely to be, think of the first models that estimated how sensitive the climate is to human influence back in the 1970s.
Hopefully, the strong evidence base we have presented today will inform a global strategy and strong local preventive action. The plastic pollution challenge can be substantially controlled within a generation’s time. So, is anyone ready to act?
As COVID-19 restrictions start to ease, we’re unlikely to return to our previous behaviours, from our work-life balance to maintaining good hygiene.
But there are downsides to this new normal, particularly when it comes to hygiene concerns, which have led to an increase in an environmental scourge we were finally starting to get on top of: single-use plastics.
We’ve recently published research based on data collected in mid-2019 (before COVID-19). Our findings showed that not only were people avoiding single-use plastics most of the time, but one of the biggest motivators was knowing others were avoiding them too. Avoidance was becoming normal.
But then COVID-19 changed the game. Since the pandemic started, there has been a significant increase in plastic waste, such as medical waste from protective equipment such as masks, gloves and gowns, and increased purchases of sanitary products such as disposable wipes and liquid soap.
The good news is we can return to our plastic-avoiding habits. It just might look a little a different.
Avoidance was more normal than we realised
In our representative survey of 1,001 Victorians, we asked people about their behaviours and beliefs around four single-use plastic items: bags, straws, coffee cups and take-away containers.
We found people’s beliefs about how often others were avoiding these items was one of the strongest predictors of their own intentions.
Other influences that predicted intentions included personal confidence, the perceived self and environmental benefits and financial costs associated with avoidance, and whether others would approve or disapprove of the behaviour.
While beliefs about other peoples’ behaviour was one of the strongest predictors of intentions, there was still a gap between these beliefs and reported behaviour.
On average, 70% of our sample reported avoiding single-use plastics most of the time. But only 30% believed others were avoiding them as often.
Thankfully, our findings suggest we can encourage more people to avoid single-use plastics more often by sharing the news that most people are doing it already. The bad news is that COVID-19 has increased our reliance on single-use items.
Some single-use is necessary during a pandemic
Just when avoidance was becoming normal, the pandemic brought single-use plastics back into favour.
Our research focused on public single-use plastic avoidance behaviours, but now is a good time to look at private ones too.
There are plenty of single-use plastics in the home: cling wrap, coffee pods, shampoo and conditioner bottles, disposable razors and liquid soap dispensers to name a few.
But you can find reusable alternatives for almost everything: beeswax or silicone wraps, reusable coffee pods, shampoo and conditioner bars, reusable safety razors and bars of soap, rather than liquid soap.
Buying cleaning products in bulk can also reduce plastic packaging and keeping glass jars or hard plastic containers are great for storing leftovers.