How are plastics harming marine ecosystems?

The oceans have become a waste-sink for plastics—just like the atmosphere is for greenhouse gas emissions. A higher carbon price may help tackle both problems.

Plastics are great materials: durable, light and easily mouldable. This explains their widespread use – over the past five decades, annual production has increased by approximately 9% a year, reaching a total of 380 million tonnes.

But only a small fraction—9%—of all the plastic ever produced has been recycled. Some plastic waste is safely stored in landfills or has been incinerated. Still, about 30% of the yearly production currently leaks out into the environment from where it ultimately ends up in the ocean, causing multiple problems for the marine ecosystem.

Figure 1: Projected ocean microplastics, accumulation by emissions scenario

Source: Lebreton et al. (2019)

Ocean plastic spoils beaches and harms wildlife. Fishing lines, ropes and nets make up over half of the plastic pollution in the Pacific Ocean. Known as ghost gear, this discarded equipment poses a serious threat to ocean wildlife. As demand for fish increases around the world, so too will plastic. According to one study, at the current rate, by 2050 there could be more plastic in the sea than fish.

Figure 2: Fish caught, by continent (million tonnes)

Source: FAO

Once in the ocean, plastic breaks down into smaller particles called microplastics. These are ingested by fish, seabirds and marine mammals, from where they enter the human food chain. Microplastics may have toxic effects on humans and marine life that are not yet fully understood.

Other harms of plastic pollution are better known: the economic costs for tourism, shipping and fishing alone have been estimated at around $13 billion a year. Overfishing and climate change potentially pose even greater threats to marine life, biodiversity and the health of the oceans. Hotter and more acidic oceans will result in the loss of coral reefs, which are a keystone species for many marine ecosystems. The IPCC places the overall cost of unabated human effects on ocean quality at $1.9 trillion a year by 2100.

When it comes to their root causes, there is a parallel between climate change and plastic pollution. Both our oceans and atmosphere are overused, and some of this is due to a lack of what economists call ‘property rights’. With no owners, there is no clear responsibility for their protection. And in the absence of prices (which an owner could charge for their use), they end up as waste-sinks for plastics and greenhouse gas emissions, respectively.

Unlike greenhouse gases, where the rich world and China are still responsible for most emissions, marine plastic disproportionately originates from developing countries because of fewer possibilities for recycling and more common landfill leakages, as well as illegal dumping. Policies should be targeted towards helping these countries build the capacity to recycle their plastics or store them safely.

Figure 3: Plastic waste by river (thousand tonnes, 2015)

Source: Lebreton et al. (2019)

Economics explains why relying on voluntary changes in consumer behaviour alone is not going to work for either stabilising the climate or reducing plastic problem. Individuals are tempted to ‘free-ride’ on the action of others and do not take account of the full cost of their choices. Economists use the term ‘collective action problems’ to describe this type of dilemma, notably studied by Nobel laureate Elinor Ostrom.

In some instances, appealing to social norms or nudging households towards more sustainable behaviour can be helpful. This may be especially true for some forms of plastics consumption. Promoting the use of reusable plastic bottles or shopping bags is relatively unintrusive and plays into consumer psychology: it is an easy way to signal pro-environmental attitudes and adherence to social norms, as well as creating a feeling of making an immediate impact. But switching to such products is just the tip of the iceberg when it comes to avoiding plastics pollution.

For climate change the fact that the damage caused by our actions is so hard to see is an even bigger problem. Our choices affect people living in the future or in distant countries, yet cutting our emissions or consumption requires costly lifestyle changes. Human traits that typically support cooperation in small groups—for example, a tendency to reciprocate the good behaviour of others or punish free-riders—are far harder to sustain when it comes to global environmental problems where those who cause the damage and those harmed never meet.

We lack information too. For emissions or plastic pollution, it is hard to grasp the total environmental impact of consumer choices. Without extra information, it is almost impossible to compare the relative climate costs of two different products. Carbon pricing is a potential solution: by introducing a global carbon price, carbon-intensive goods would become relatively more expensive. All customers need to do is something with which they are already familiar: compare the prices of different products.

Carbon pricing would help with plastic pollution too, by making plastics less attractive than more sustainable materials. Their production is relatively energy-intensive and, in its conventional form, requires fossil fuels as a raw material. Plastics production in 2015 accounted for roughly 4% of global emissions. The damage from plastic would be lower if bio-based plastics replaced conventional plastics, and recycling rates were higher. These goals are supported by higher carbon prices.

Innovative technologies that help to break the link between pollution and consumption are essential if we want to preserve current living standards while saving the planet. New types of plastics—for example, polylactic acids—use raw materials like starch, which are easily derived from renewable sources such as corn or potatoes. Not only do they share some of the valuable properties of existing plastics, but they are also biodegradable, reducing their impact on marine environments. But their production is currently more expensive and requires energy that should come from renewable sources to reduce their carbon footprint.

Pricing emissions can help to speed up the required innovations in clean energy. The EU’s emissions trading system may have increased low-carbon innovation by energy firms by 10%, a recent study shows. A more ambitious approach would be to provide additional funding for basic research. Technology transfers can also be used to help developing countries avoid marine plastic pollution.

Plastic pollution garners attention. Its effects resonate with the public in a world where images are so important: clips of dolphins playing with plastic bags and turtles trapped in beer holders have become central rallying calls in anti-pollution campaigns. Solving the problem may rely on a simple piece of economics that the public will have to get used to: plastic needs a higher price.

Where can I find out more?

Pricing plastics pollution: Lessons from three decades of climate policy: Jonas Monast and John Virdin discuss policy solutions beyond plastic bans and taxes and recycling improvements
Marine plastic pollution: Sources, impacts, and policy issues: Bethanie Carney Almroth and Håkan Eggert on plastic pollution and its potential effects on marine ecosystems and human health
A framework for selecting and designing policies to reduce marine plastic pollution in developing countries: Francisco Alpizar and co-authors introduce tracing the flow plastics through the socioeconomic system and identify market-based and behavioural tools to reduce marine plastic waste