The connections between plastic and climate change are far deeper than we all realise. It is already widely recognised that plastic production relies on fossil fuels, directly contributing to worsening climate change. However, recent scientific findings have shown that macro plastics also emit greenhouse gases when they degrade into microplastics. Worse still, microplastic pollution alters the ocean’s climate mitigation potential by reducing both its blue carbon storage capacity and its resilience to climate change. Ahead of COP26, countries’ delegates must recognise and acknowledge these scientific links in their updated national strategies to keep warming below 1.5⁰ Celsius.

Degrading macro plastics release greenhouse gases

Plastic pollution contributes to climate change in more complex ways that previously understood. Once exposed to solar radiation, macro plastic undergoes gradual degradation and fragmentation processes, releasing powerful greenhouse gases into the atmosphere. Sea surface plastic degradation alone has been estimated to release 76 metric tonnes of methane annually worldwide. Methane is 36 times more potent than CO2 in producing greenhouse effects, and it directly contributes to climate change.

Microplastic pollution hinders the ocean’s climate mitigation potential

Oceans absorb a significant amount of all greenhouse gases produced on our planet – as much as 40% of all human-produced carbon dioxide since the beginning of the industrial era.

Microplastic pollution directly hinders the ocean’s climate mitigation power by interfering with the flow of carbon in the ocean. That “biological carbon pump” sees microscopic plants (phytoplankton) and animals (zooplankton) capture carbon on the ocean surface and transport it into the deep ocean, preventing it from re-entering the atmosphere. Laboratory experiments suggest that phytoplankton contaminated with microplastics are less able to fix carbon through photosynthesis. Similarly, contaminated zooplankton have lower metabolic rates, reproductive success, and survival rates.

Fish and marine life also play a key role in the ocean’s biological carbon pump and are significantly negatively affected by microplastics. Fish-produced faecal pellets are one of the most efficient natural mechanisms of carbon storage, locking it deep in the ocean for up to 600 years. However, 33% of fish world-wide have ingested microplastics. Microplastic in faecal pellets makes them lighter negatively affecting their sinking and, thus, their carbon storage function. Moreover, toxic additives are released by microplastics and absorbed by fish and other marine fauna, causing a range of significant harm, from energy depletion and fertility issues to behavioural problems and early death. Harmful concentrations of microplastics increase as they go up the trophic web, harming not only fish but also entire ecosystems and reducing the ocean’s resilience to climate change.


Urgent action is needed if we are to meet our climate goals.

Some plastic polymers release more powerful greenhouse gases than others. Low-density polyethylene is commonly used throughout the world in single-use packaging and bags, and is the most prevalent plastic discarded in the ocean. Adopting ambitious measures to phase out single-use plastics, plastics that emit most greenhouse gases, and plastics that easily degrade into microplastics (low-quality plastics) will help against climate change.

Preserving essential marine life requires the reduction – and eventual elimination – of large amounts of macro plastics entering the ocean each year. Preventive measures include marking and tracking fishing nets and plastic containers, allowing them to be retrieved when lost at sea, and capitalising on fishing net high recycling potential. The direct release of microplastics into the environment should also be addressed, through international phasing out of microplastics voluntarily added to products (e.g. glitter on artificial flowers, polystyrene stuffing in children toys), as well as the mandatory confinement of industry facilities that produce or handle the virgin/recycled plastic pellets used in most plastic products.

With global plastic production expected to increase exponentially in the coming years, preventive measures alone are not enough to reverse the microplastic pollution curve. We urgently need to interrogate our dependence on plastic, rethinking and reshaping how we make and use plastic. Our planet is at stake and nothing short of bold decisions will do. COP26 is an important opportunity to act on the harm microplastics represent to our climate and to the ocean’s climate mitigation potential.