Cleaner seas: reducing marine pollution.

In the age of the Anthropocene, the ocean has typically been viewed as a sink for pollution. Pollution is varied, ranging from human-made plastics and pharmaceutical compounds, to human-altered abiotic factors, such as sediment and nutrient runoff. As global population, wealth and resource consumption continue to grow, so too does the amount of potential pollution produced. This presents us with a grand challenge which requires interdisciplinary knowledge to solve. There is sufficient data on the human health, social, economic, and environmental risks of marine pollution, resulting in increased awareness and motivation to address this global challenge, however a significant lag exists when implementing strategies to address this issue. This review draws upon the expertise of 17 experts from the fields of social sciences, marine science, visual arts, and Traditional and First Nations Knowledge Holders to present two futures; the Business-As-Usual, based on current trends and observations of growing marine pollution, and a More Sustainable Future, which imagines what our ocean could look like if we implemented current knowledge and technologies. We identify priority actions that governments, industry and consumers can implement at pollution sources, vectors and sinks, over the next decade to reduce marine pollution and steer us towards the More Sustainable Future. Supplementary Information: The online version contains supplementary material available at 10.1007/s11160-021-09674-8.

Introduction

The ocean has historically been a sink for pollution, leaving modern society with significant ocean pollution legacy issues to manage (Elliott and Elliott 2013; O'Shea et al. 2018). People continue to pollute the ocean at increasing rates creating further damage to marine ecosystems. This results in detrimental impacts on livelihoods, food security, marine navigation, wildlife and well-being, among others (Krushelnytska 2018; Lebreton and Andrady 2019; Nichols 2014; Seitzinger et al. 2002). As pollution presents a multitude of stressors for ocean life, it cannot be explored in isolation (Khan et al., 2018). Thus, global coordinated efforts are essential to manage the current and future state of the ocean and to minimise further damage from pollution (Krushelnytska 2018; Macleod et al. 2016; O'Brien et al. 2019; Williams et al. 2015). Efforts are also needed to tackle key questions, such as how do pollutants function in different environments, and interact with each other?

Pollution can be broadly defined as any natural or human-derived substance or energy that is introduced into the environment by humans and that can have a detrimental effect on living organisms and natural environments (UNEP 1982). Pollutants, including light and sound in addition to the more commonly recognised forms, can enter the marine environment from a multitude of sources and transport mechanisms (Carroll et al. 2017; Depledge et al. 2010; Longcore and Rich 2004; Williams et al. 2015). These may include long range atmospheric movement (Amunsen et al. 1992) and transport from inland waterways (Lebreton et al. 2017).

Current pollutant concentrations in the marine environment are expected to continue increasing with growth in both global population and product production. For example, global plastic production increased by 13 million tonnes in a single year (PlasticsEurope 2018), with rising oceanic plastic linked to such trends (Wilcox et al. 2020). Pharmaceutical pollution is predicted to increase with population growth, resulting in a greater range of chemicals entering the ocean through stormwater drains and rivers (Bernhardt et al. 2017; Rzymski et al. 2017). Additionally, each year new chemical compounds are produced whose impacts on the marine environment are untested (Landrigan et al. 2018).

Marine pollution harms organisms throughout the food-web in diverse ways. Trace amounts of heavy metals and persistent organic pollutants (POPs) in organisms have the capacity to cause physiological harm (Capaldo et al. 2018; Hoffman et al. 2011; Salamat et al. 2014) and alter behaviours (Brodin et al. 2014; Mattsson et al. 2017). Artificial lights along coasts at night can disrupt organism navigation, predation and vertical migration (Depledge et al. 2010). Pharmaceutical pollutants, such as contraceptive drugs, have induced reproductive failure and sex changes in a range of fish species (Lange et al. 2011; Nash et al. 2004). Furthermore, some pollutants also have the capacity to bioaccumulate, which means they may become more concentrated in higher trophic marine species (Bustamante et al. 1998; Eagles-Smith et al. 2009).

Pollution also poses a huge economic risk. Typically, the majority of consequences from pollution disproportionately impact poorer nations who have less resources to manage and remediate these impacts (Alario and Freudenburg 2010; Beaumont et al. 2019; Golden et al. 2016; Landrigan et al. 2018). Marine pollution can negatively impact coastal tourism (Jang et al. 2014), waterfront real estate (Ofiara and Seneca 2006), shipping (Moore 2018) and fisheries (Hong et al. 2017; Uhrin 2016). Contamination of seafood poses a perceived risk to human health, but also results in a significant financial cost for producers and communities (Ofiara and Seneca 2006; White et al. 2000). Additionally, current remediation strategies for most pollutants in marine and coastal ecosystems are costly, time consuming and may not prove viable in global contexts (Ryan and Jewitt 1996; Smith et al. 1997; Uhrin 2016).

Reducing marine pollution is a global challenge that needs to be addressed for the health of the ocean and the communities and industries it supports. The United Nations proposed and adopted 17 Sustainable Development Goals (SDGs) designed to guide future developments and intended to be achieved by 2030. It has flagged the reduction of marine pollution as a key issue underpinning the achievement of SDG 14, Life Under Water, with target 14.1 defined as “prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution” by 2025 (United Nations General Assembly 2015). In the UN Decade of Ocean Science (2021–2030), one of the six ocean outcomes relates specifically to the identification and reduction of marine pollution (A Clean Ocean; UN DOS SD). The task of reducing marine pollution is daunting—the ocean is so vast that cleaning it seems almost impossible. However, effective management of pollution at its source is a successful way to reduce it and protect the ocean (DeGeorges et al. 2010; Rochman 2016; Simmonds et al. 2014; Zhu et al. 2008). Strategies, implemented locally, nationally and globally, to prevent, or considerably reduce pollution inputs in combination with removing pollutants from the marine environment (Sherman and van Sebille 2016) will allow healthy ocean life and processes to continue into the future. However, such strategies need to be implemented on a collective global scale, and target pollution at key intervals from their creation to their use and disposal.

To help explain how society can most effectively address pollution sources and clean the ocean, we depict two different future seas scenarios by 2030. The first is a Business-As-Usual scenario, where society continues to adhere to current management and global trends. The second is a technically achievable, more sustainable future that is congruent with the SDGs, and where society actively take actions and adopt sustainable solutions. We then explore pollution in three ‘zones’ of action; at the source(s), along the way, and at sink, in the context of river or estuarine systems, as water-transported pollution is commonly associated with urban centres alongside river systems (Alongi and McKinnon 2005; Lebreton et al. 2017; Lohmann et al. 2012; Seitzinger and Mayorga 2016).

Methods

As a group of interdisciplinary scientists, with expertise in marine pollution, we participated in the Future Seas project (www.FutureSeas2030.org), which identified marine pollution as one of 12 grand challenges, and followed the method outlined in Nash et al. (2021). The process involved a structured discussion to explore the direction of marine social-ecological systems over the course of the UN Decade of Ocean Science, specific to marine pollution. The discussion resulted in developing two alternate future scenarios of marine pollution, a ‘Business-As-Usual’ future that is the current trajectory based on published evidence, and a ‘more sustainable’ future that is technically achievable using existing and emerging knowledge and is consistent with the UN’s Sustainable Development Goals. To ensure a wide range of world views were present in the future scenarios, Indigenous Leaders and Traditional Knowledge Holders from around the world came together and presented their views, experiences and identified their priorities to remove and reduce marine pollution (Nash et al. 2021; Fischer et al. 2020).

We defined the scope of our paper by identifying key pollutant sources, types and drivers of marine pollution (Table 1 for pollutant sources and types; see "Future Narratives" below). We then developed a list of feasible actions that could drive the current state of the ocean towards a cleaner, more sustainable future (Supplementary Table 1). From these actions we deliberated as a group and identified ten actions that have high potential to be implemented within the next decade and significantly reduce marine pollution (Fig. 1). The linkages between our ten priority actions and the SDGs are outlined in Supplementary Table 2.

Table 1

A list of the three major sources of marine pollution and examples of the key types of pollution from each

source considered in our future scenarios. * denotes a pollutant that is outside the scope of this paper

	Pollutant Source
Pollutant Type	Land-based industry	Municipal-based	Sea-based industry
Sediment	Sediment from mining*, agriculture, or forestry	Sediment from coastal development	Sediment disruptions (e.g. dredging and aquaculture)
Nutrient	Nutrients (e.g. nitrogen, phosphorous, iron) from agriculture, forestry, livestock	Nutrients (e.g. nitrogen and phosphorous) from wastewater, stormwater	Increase in nutrients (e.g. nitrogen and phosphorous) from aquaculture
Plastics	Plastics from packaging and transport of products	Plastics from urban stormwater, and litter escaped from waste management systems	Abandoned, lost, or discarded fishing gear from vessels.Plastics from aquaculture, shipping and offshore structures
Pharmaceuticals	Pharmaceuticals used in animal agriculture	Pharmaceuticals in wastewater from household waste, and medical facilities	Pharmaceuticals (e.g. anti-biotics and antiparasitic drugs) from aquaculture
Chemicals	Chemicals, POPs and pesticides from agriculture, mining, industrial wastewater and runoff	Petroleum and household chemicals from wastewater, and stormwater outlets	Petroleum and chemicals from shipping and offshore structures
Sound			Motor noise, seismic devices and sound propagating devices
Light*		Light from coastal development*	Light from offshore structures and marine transport*
Water*		Fresh water/ heated water* (e.g. melted sea ice, shifts in ocean currents)
Nuclear Waste*	Nuclear waste from power stations*

Fig. 1

Ten actions that can substantially reduce the amount of pollution entering the marine environment. Actions are placed along the system where they could have the greatest impact at reducing pollution: at the

source of the pollutant (at the source), once the pollutant is released (along the way), once the pollutant has entered the ocean (at the sink) or at multiple points along the system (bottom arrow). * indicates actions that could be successfully implemented well before the next decade to significantly reduce pollution

Future narratives

We identified three broad sources of marine pollution: land-based industry, sea-based industry, and municipal-based sources and the most significant types of pollution characteristic of each source (Table 1). We framed our two contrasting future scenarios (Business-As-Usual and a technically feasible sustainable future), around these pollutants and their sources (Table 2). In addition to these future narratives, we reflect on the present impacts that pollution is currently having on the livelihoods and cultures of First Nations peoples and Traditional Knowledge Holders. We include the narratives of the palawa pakana people, from lutruwita/Tasmania (Table 3), and the Greenlandic Inuit people (Table 4).

Table 2

The method resulted in two futures, which focus on pollutants outlined in Table 1. The two futures are told here in a narrative format. The Business-As-Usual (BAU) future has been informed by current trends and predictions in marine pollution. The technically feasible sustainable future imagines what the future may be like should we implement the actions outlined in this paper

A wasted opportunity (Business-As-Usual future) People have forgotten or ignored that their world is mostly ocean. Immersed in our virtual lives, people are disconnected from their environment. Unchecked growth is status quo. Surrounded by rising quantities of pollution, people do not see the sea, although they peer in wonder at the polluted waves breaking on their shores, while peeling back the plastic from their shrink-wrapped vegetables and listening to the constant hum of marine traffic travelling across the seas. Politicians pontificate but laws are toothless, made then broken, useless distractions from the real issue. Our media is swamped with images of dead seabirds, turtles and fish, and marine species entangled in fishing gear or plastics. News of die-offs from eutrophication or toxic pollution episodes is a regular occurrence. The marketing alongside these news stories on our screens is still telling us to buy more, consume more. The growing global population in combination with an increasing rural–urban migration has intensified demands on waste collection and treatment systems, urban drainage and coastal development. Although some regions, cities and industries have adopted the sustainable practices recommended by the UN to meet the SDGs, the majority struggle to manage the resource and waste demands of their rapidly growing urban populations. As a result, the amount of untreated wastewater entering the ocean has escalated. Grass-roots movements to educate and encourage communities to adopt sustainable, less wasteful products and practices continue to grow. Positive changes can be seen in those communities. However, the slow voluntary changes made by industry and the lack of enforcement/legislation made by governments has allowed marine pollution to increase and the warnings we heard ten years ago on the implications this will have on our health and livelihoods have become reality Stemming the flow and proceeding with caution (technically feasible sustainable future): The ocean is acknowledged for the goods and services it provides and viewed with appreciation and opportunity. People understand our impact on the sea and its life-supporting role for us and society acts in accordance with this view. We recognise that cleaning our ocean and addressing SDG 14, Life Below Water, we also contribute to SDG 15, Life on Land. Pollution clean-up efforts are targeted to most effective and feasible sites, at the pollutant source, along their way to the sea, and at their ocean sink. Technology is used to prevent, filter, clean, repair and restore our shores, the water column and the seabed floor. The demand for re-useable, less-toxic and less-packaged products means that manufactures have shifted to sustainable production and packaging of goods, contributing to the achievement of SDG 12, responsible production and consumption. Government standards require recycled materials to be used in the manufacturing of new products, and there is a viable, thriving circular economy. Citizen scientists roam the shores, reporting and sharing their data with the world. Volunteer community groups continue to clean the beaches of rubbish and are starting to collect fewer items each visit. Guided by science and indigenous knowledge, politicians adopt the precautionary principle and our laws are equitable, enforced and effective. Wealthy nations have started to responsibly manage their waste and are gradually ceasing exports of their waste to poorer nations. Across the globe more and more regions, cities and industries are meeting SDG targets, adopting sustainable practices that suit their culture and landscape. Breeding grounds for marine mammals are protected from noise propagating devices and the revegetation of inland waterways and wetlands are progressing. Shifts to more sustainable agricultural practices have removed the reliance on large applications of fertilisers and as such eutrophication events are falling. The health and well-being of communities and life is on the rise

Table 3

In lutruwita (Tasmania), Marineer Shell (Phasianotrochus rutilus) necklace making is a palawa pakana traditional practice that has continued over thousands of years. Shell-necklaces were once crafted as jewellery and used for trade purposes. King, Queen and standard marineers were not just palawa nicknames handed down through generations, status was allocated to each of the marineer species and the resulting necklaces. Necklaces were reflective of the status allocated to the owner from the creator, and clan as a whole. Here, Elder and shell-necklace maker, Lola Greeno, shares her account of the current impacts of pollution on her art and culture. (Photo credit: Dean Greeno)

“To harvest the marina shells, it requires the shell collector, to first study the tide level to find out what day of the month and the time of the day, that the tide level will be less than half a metre. Experienced collectors will be on the beach just before low tide, allowing time to set up as the tide runs out and gives a couple of hours to gather before the tides starts coming back into shore. The low tide needs to be during daylight hours as safety precaution. In a calendar year, the shell collectors may get two good tides for gathering. The shell collector tries to gather enough to last 12 months. They need about a sugar bowl full to freeze and mix with other shells to create her patterns for a number of pieces in a year. The regime allows time for the shells to continue to spawn. The full cycle from where the shells go out into 30 feet of water to breed drop the roe and come into shore and grown fully by end of April In the last 10 years we have seen a gradual change to seabeds and collection areas around Flinders Island. In some collecting seasons, very few shells are available to harvest. We have seen a site close to shore, where land run-off into the sea, makes the shells have acid burnt tips. We have seen areas where the kelp is very scarce in the bay where many recreational boats are moored. The boat slip has almost wiped out one species with run off from boats paints. In one bay we saw a lot of grey algae and next bay where there is an abalone fish farm, if the abalone escape, they compete with the marina shells for food. The other competition is from the global warming of water temperature. The non-science person does not understand the pollution risks or what the warmer sea does to spawning mollusc of the marina shells.”

Table 4

Pollution disproportionally impacts first nations people. To the Inuit Greenland peoples, pollution from the Outer World presents a vast array of challenges. Documented here is a firsthand account of some types of pollutants in Greenland and impacts these have on Inuit communities. We have the capacity to influence pollution impacts on a local scale, but we require political efforts, legislation, and global change to make positive impacts in communities and environments in need. (Photo credit: Jonathan Stark)

Year in the Greenlandic Inuit language is ukioq, which is actually the same word for winter. Winter lasts most of a year. There is snow and there is ice, saltwater ice and freshwater ice, snow covered ice and icebergs. White in varying shades depending first and foremost on the angle and intensity of incoming light, be it stars, moonlight, the sky, clouds, northern lights – yes, and of course the sun. There are periods in winter and in late fall where the sun is low that give these reddish nuances at first sunrise and late sunset, similar though different, that give you flaming reddish icebergs. In overcast weather the same icebergs can radiate beautifully blue nuances. Such a description depicts pristine nature, literally clean in all aspects of the word. The air is very low on humidity the further north of the arctic circle you get. That feels fresh and clean, too There was once a group of scientists doing field work in the north-east of Greenland a couple of decades ago. One day they had split up into two groups, there was a smoker in one of the groups. The groups went up on both sides of a glacier on foot. In the middle of the day there was barely any wind, one group was taking a lunch break in the most magnificent weather when one of them suddenly said, “I smell cigarette smoke”. They noted the time and place. When they met up with the other group it was confirmed that the smoker had smoked a cigarette around the noted time. On the map they checked where they were – they had been 5 km. apart Foreign scientists discovered a few years back on the Greenland inland ice that although it looked white and clean, the topsoil was polluted and most polluted in spring. Even animals, such as polar bears have high levels of PCB and other foreign materials. Most of this pollution comes from the Euro-Asian continent. This is pollution from the Outer World From former military outposts there are often deposits of hundreds of barrels of oil and fuel, abandoned, to rust away and the oil and fuel to enter the ecosystem over a prolonged time. Another pollution from the local area is from mining sites. Mussels, fish and birds feeding in polluted inlets all had high concentrations of pollution. Harvesting was banned. Regulation now applies to this type of pollution Sewage from households and industry flow directly into the sea without filtration. Combustibles from households and industry are burned either in open air at dump sites (very common) or in an incinerator. The smell of the smoke is said to be terrible. Iron, chemicals, used batteries, used motor oil and more are piled up. Boats, engines, cars, and snowmobiles are left as litter in towns. In recent years some towns have begun to collect such waste and send it to treatment facilities in Denmark, some are kept for spare parts, others were supposed to go to the dump. This is consumer generated pollution Outside town limits and village limits where locals go fishing, hunting or go for recreational purposes, be it on day trips or longer trips, some people bring back their trash, burn it or bury it on site. Some just leave it as is to be scattered by fox, raven, gulls or the wind. Occasionally some dump it in a large plastic bag in the sea a few meters from the shore on shallow water where it is discernible. Such behaviour is new and is absolutely banned but has been observed a few times in a few places also by rivers where there is arctic char. This might have been done by town people on a recreational trip who have begun to act counterproductively – they are known to react against foreigners, in this case usually Danes who tell them not to litter in nature. They react because in their mind it is their country, and no foreigner has the right to tell them what to do with their country. It also proves that they have lost their connection to their cultural heritage. This is pointless pollution

Drivers

We identified three key drivers that will substantially contribute to an increasingly polluted ocean if no actions are taken to intervene; societal behaviours, equity and access to technologies, and governance and policy. Alternatively, these pollution drivers can be viewed as opportunities to implement strategic measures that shift the trajectory from a polluted marine environment to a healthier marine environment. Below we highlight how current societal behaviours, lack of implementation of technological advancements, and ocean governance and policy making contribute to an increasingly polluted ocean and drive society towards a BAU future (Table 2). Importantly, we discuss how changes in these behaviours, and improvements in technologies and governance can lead to reduced marine pollution, ultimately driving a cleaner, more sustainable ocean for the future.

Societal behaviour

Societal behaviours that drive increasing pollution in the world’s ocean

A consumer culture that prioritizes linear production and consumption of cheap, single-use materials and products over circular product design and use (such as, reusable products or products that are made from recycled material), ultimately drives the increased creation of materials. Current production culture is often aligned with little consideration for the socioeconomic and environmental externalities associated with the pollution that is generated from a product’s creation to its disposal (Foltete et al. 2011; Schnurr et al. 2018). Without a dedicated management strategy for the fate of products after they have met their varying, often single-use objectives, these materials will enter and accumulate in the surrounding environment as pollution (Krushelnytska 2018; Sun et al. 2012). Three examples of unsustainable social behaviours that lead to products and materials ending up as marine pollution are: (1) the design and creation of products that are inherently polluting. For example, agricultural chemicals or microplastics and chemicals in personal care and cosmetic products. (2) social behaviours that normalize and encourage consumption of single-use products and materials. For example, individually wrapped vegetables or take-away food containers. (3) low awareness of the impacts and consequences and therefore the normalization of polluting behaviours. For example, noise generation by ships at sea (Hildebrand 2009) or the large application of fertilizers to agricultural products (Sun et al. 2012).

Shifting societal behaviours towards sustainable production and consumption

A cleaner ocean with reduced pollution will require a shift in production practices across a wide array of industries, as well as a shift in consumer behaviour. Presently, consumers and industry alike are seeking science-based information to inform decision making (Englehardt 1994; Vergragt et al. 2016). Consumers have the power to demand change from industries through purchasing power and social license to operate (Saeed et al. 2019). Policymakers have the power to enforce change from industries through regulations and reporting. Aligning the values between producers, consumers and policymakers will ensure best practices of sustainable consumption and production are adopted (Huntington 2017; Moktadir et al. 2018; Mont and Plepys 2008). Improved understanding of the full life cycle of costs, consequences (including internalised externalities, such as the polluter-pays-principle (Schwartz 2018)), materials used, and pollution potential of products could substantially shift the trajectory in both production and consumerism towards cleaner, more sustainable seas (Grappi et al. 2017; Liu et al. 2016; Lorek and Spangenberg 2014; Sun et al. 2012). For example, economic policy instruments (Abbott and Sumaila 2019), production transparency (Joakim Larsson and Fick 2009), recirculation of materials (Michael 1998; Sharma and Henriques 2005), and changes in supply-chains (Ouardighi et al. 2016) are some of the ways production and consumerism could become more sustainable and result in a cleaner ocean.

Equity and access to technologies

Inequitable access to available technologies

Despite major advancements in technology and innovation for waste management, much of the current waste infrastructure implemented around the world is outdated, underutilised, or abandoned. This is particularly the case for rapidly developing countries with large populations who have not had access to waste reduction and mitigation technologies and systems employed in upper income countries (Velis 2014; Wilson et al. 2015). The informal recycling sector (IRS) performs the critical waste management role in many of the world’s most populous countries.

Harnessing technologies for today and the future

Arguably, in today’s world we see an unprecedented number and types of technological advances stemming from but not limited to seismic exploration (Malehmir et al. 2012), resource mining (Jennings and Revill 2007; Kampmann et al. 2018; Parker et al. 2016), product movement (Goodchild and Toy 2018; Tournadre 2014) and product manufacturing (Bennett 2013; Mahalik and Nambiar 2010). Applying long term vision rather than short term economic gain could include supporting technologies and innovations that provide substantial improvements over Business-As-Usual. For example, supporting businesses or industries that improve recyclability of products (Umeda et al. 2013; Yang et al. 2014), utilize waste (Korhonen et al. 2018; Pan et al. 2015), reduce noise (Simmonds et al. 2014), and increase overall production efficiency will substantially increase the health of the global ocean. Efforts should be made wherever possible to maintain current waste management infrastructure where proven and effective, in addition to ensuring reliance and durability of new technologies and innovations for improved lifespan and end of life product management. Consumer demand, taxation, and incentives will play a necessary roll to ensure the appropriate technologies are adopted (Ando and Freitas 2011; Krass et al. 2013).

Governance and policy

Lack of ocean governance and policy making

The governance arrangements that address marine pollution on global, regional, and national levels are complex and multifaceted. Success requires hard-to-achieve integrated responses. In addition to the equity challenges discussed in Alexander et al. (2020) which highlight the need for reduced inequity to improve the susatinability of the marine enviornemnt, we highlight that land-based waste is the largest contributor to marine pollution and therefore requires governance and policies that focus on pollution at the source. Current regulations, laws and policies do not always reflect or address the grand challenge of reducing marine pollution at the source. The ocean has traditionally been governed through sectoral approaches such as fisheries, tourism, offshore oil and mining. Unfortunately, this sector approach has caused policy overlap, conflict, inefficiencies and inconsistencies regarding marine pollution governance (Haward 2018; Vince and Hardesty 2016). Although production, manufacturing, and polluting may largely take place under geo-political boundaries, pollution in the high seas is often hard to assign to a country of origin. This makes identifying and convicting polluters very difficult (Urbina 2019). For example, the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) has been criticised as ineffective in reducing marine pollution, largely due to the lack of easily monitoring, identifying and convicting offenders (Henderson 2001; Mattson 2006).

Harnessing ocean governance and policy

Binding domestic policies and international agreements are regulatory levers that can drive change at local, community, state, federal and international scales (Vince and Hardesty 2018). The UN Law of the Sea Convention Part XII (articles 192–237) is dedicated to the protection and preservation of the marine environment and marine pollution is addressed in article 194. It also sets out the responsibilities of states and necessary measures they need to undertake to minimise pollution their own and other jurisdictions. While the Law of the Sea recognises the differences between sea-based and land-based pollution, it does not address the type of pollutants and technical rules in detail. Voluntary measures including MARPOL 73/78 (IMO 1978), United Nations Environment Assembly resolutions (UNEA 2019) and the FAO voluntary guidelines for the marking of fishing gear (FAO 2019), already exist in an attempt to reduce specific components of marine pollution. However, the health of marine ecosystems would benefit from multilateral international or regional agreements that minimise the production of items or the use of processes that result in high levels of marine ecosystem harm. For example, international regulation for underwater sound (McCarthy 2004), policies to reduce waste emissions (Nie 2012) and the polluter pays principle (Gaines 1991) are policies and agreements that could minimise pollutants entering the marine ecosystem. Global and regional governance can create a favourable context for national policy action. Policies that adapt to shifts in climate and are guided by science and indigenous knowledge could be more likely to succeed (Ban et al. 2020).

Actions to achieve a more sustainable future

The grand challenge of reducing ocean pollution can seem overwhelming. However, there are myriad actions, interventions and activities which are highly feasible to implement within the next decade to rapidly reduce the quantity of pollution entering the ocean. Implementing these actions requires collaboration among policymakers, industry, and consumers alike. To reduce pollution from sea-based industries, land-based industries and municipal-based pollutants (Table 1), we encourage the global community to consider three ‘zones’ of action or areas to implement change: at the source(s), along the way/along the supply chain, and at sinks (Fig. 1). It is important to highlight that action cannot be implemented at any one zone only. For example, repeated clean ups at the sink may reduce pollution in an area for a time, but will not stem the flow of pollutants. Rather, action at all three zones is required if rapid, effective reductions of ocean pollution are to occur.

Actions at the source(s)

Reducing pollution at its multitude of sources is the most effective way to reduce and prevent marine pollution. This is true for land-based industry pollutants, sea-based industry pollutants and municipal-based pollutants. An example for each includes; reduction in fertilizer leading to less agricultural runoff in coastal waters (Bennett et al. 2001), changes in packaging materials may see reductions in production on a per item basis, and a lowered frequency and timing of seismic blasting would result in a decrease in underwater noise pollution at the source. The benefits of acting at the source are powerful: if a pollutant is not developed or used initially, it cannot enter the marine environment. Action can occur at the source using various approaches such as; prevention of contaminants, outreach campaigns, introduction of bans (or prohibitions) and incentives and the replacement of technologies and products for less impactful alternatives (Fig. 1). However, achieving public support abrupt and major changes can be difficult and time consuming. Such changes may meet resistance (e.g. stopping or changing seismic testing) and there are other factors beyond marine pollution that must be considered (e.g. health and safety of coastal lighting in communities may be considered more important than impacts of light pollution on nearby marine ecosystems). Actions such as outreach and education campaigns (Supplementary Table 2) will be an important pathway to achieve public support.

Actions along the way

Reducing marine pollution along the way requires implementation of approaches aimed at reducing pollution once it has been released from the source and is in transit to the marine environment (Fig. 1). Acting along the way does provide the opportunity to target particular pollutants (point-source pollution) which can be particularly effective in reducing those pollutants. While municipal-based pollutants can be reduced ‘along the way’ using infrastructure such as gross pollutant traps (GPTs) and wastewater treatment plants (WWTPs), some pollution such as light or sound may be more difficult to minimize or reduce in such a manner. WWTPs can successfully capture excess nutrients, pharmaceuticals and litter that are transported through sewerage and wastewater systems. However, pollution management ‘en route’ means there is both more production and more likelihood of leakage to the environment. In addition, infrastructure that captures pollution is often expensive, requires ongoing maintenance (and hence funding support), and if not managed properly, can become physically blocked, or result in increased risk to human health and the broader environment (e.g. flooding during heavy rainfall events). When considering management opportunities and risks for both land and sea-based pollution, the approaches required may be quite different, yielding unique challenges and opportunities for resolution in each (Alexander et al. 2020).

Actions at the sinks

Acting at sinks essentially requires pollution removal (Fig. 1). This approach is the most challenging, most expensive, and least likely to yield positive outcomes. The ocean encompasses more than 70% of the earth’s surface and extends to depths beyond ten kilometres. Hence it is a vast area for pollutants to disperse and economically and logistically prohibitive to clean completely. However, in some situations collecting pollutants and cleaning the marine environment is most viable option and there are examples of success. For example, some positive steps to remediate excess nutrients include integrated multi-trophic aquaculture (Buck et al. 2018). ‘Net Your Problem’ is a recycling program for fishers to dispose of derelict fishing gear (www.netyourproblem.com). Municipal-based and sea-based industry pollutants are often reduced through clean-up events. For example, large oils spills often require community volunteers to remove and clean oil from coastal environments and wildlife. Such activities provide increased awareness of marine pollution issues, and if data are recorded, can provide a baseline or benchmark against which to compare change. To address pollution at sinks requires us to prioritise efforts towards areas with high acclamations of pollution, (e.g., oil spills). Repeated removal or cleaning is unlikely to yield long term results, without managing the pollution upstream –whether along the route or at the source.

Conclusion

To achieve the More Sustainable Future, and significantly reduce pollution (thereby achieving the SGD targets in Supplementary Table 2), society must take ongoing action now and continue this movement beyond 2030. Prioritising the prevention of pollutants from their sources, using bans and incentives, outreach and education, and replacement technologies, is one of the most important steps that can be taken to shift towards a more sustainable future. Without addressing pollution from the source, current and future efforts will continue to remediate rather than mitigate the damage pollution causes to the ocean and organisms within. For pollutants that are not currently feasible to reduce at the source, collection of pollutants before they reach the ocean should be prioritised. For example, wastewater treatment plants and gross pollutant traps located at point-source locations such as stormwater and wastewater drains are feasible methods for reducing pollutants before they reach the ocean. Actions at the sink should target areas where the maximum effort per quantity of pollution can be recovered from the ocean. For example, prompt clean-up responses to large pollution events such as oil spills or flooding events and targeting clean-ups at beaches and coastal waters with large accumulations of plastic pollution.

These priority actions are not the perfect solution, but they are great examples of what can be and is feasibly done to manage marine pollution. Each action is at risk of failing to shift to a cleaner ocean without the support from governments, industries, and individuals across the whole system (from the source to the sink). Governments and individuals need to push for legislation that is binding and support sustainable practices and products. Effective methods for policing also need to be established in partnership with the binding legislation. Regardless of which zone are addressed, our actions on sea and coastal country must be guided by Indigenous knowledge and science (Fischer et al., 2020; Mustonen (in prep).

We recognise the major global disruptions which have occurred in 2020, particularly the COVID-19 pandemic. The futures presented here were developed prior to this outbreak and therefore do not consider the effects of this situation on global pollution trends. In many ways, this situation allows us to consider a ‘reset’ in global trajectory as discussed by Nash et al. (2021). Our sustainable future scenario may be considered a very real goal to achieve in the coming decade.

Below is the link to the electronic supplementary material.

Supplementary file1 (DOCX 509 kb)