The findings appear to reveal an important role for the waste material – defined as plastic fragments smaller than five millimeters in size – in a process considered crucial to regulating the Earth’s temperature.
The ubiquity of microplastics is now widely appreciated, even as significant gaps endure in our understanding of how exactly they arrive in the multitude of locations they are now found, including air, soil, Arctic ice and the bodies of humans and animals. The toxicity and ecosystem-disruption threat is assumed to be significant.
But they haven’t been connected with climate change until now. “Climate disruption and plastic pollution are two major environmental challenges that intersect in complex ways,” write the authors of a new study appearing in the Journal of Hazardous Materials: Plastics. “MPs (microplastics) influence biogeochemical processes, disrupt oceanic carbon pumps, and contribute directly to greenhouse gas (GHG) emissions.”
Lead author Dr Ihsanullah Obaidullah, Associate Professor of Integrated Water Processing Technologies at the University of Sharjah in the United Arab Emirates, said: “In marine ecosystems, MPs alter the natural carbon sequestration by affecting phytoplankton and zooplankton, which are key agents of carbon cycling. Additionally, the plastisphere, a microbial community colonizing MPs, plays a significant role in GHG (greenhouse gas production) due to its diverse microbial networks.”
While widely recognized as pollutants, “our study shows they also interfere with the ocean’s ability to absorb carbon dioxide, a process critical for regulating Earth’s temperature,” said Obaidullah.
He added, “Microplastics disrupt marine life, weaken the ‘biological carbon pump,’ and even release greenhouse gases as they degrade. Over time, these changes could lead to ocean warming, acidification, and biodiversity loss, threatening food security and coastal communities worldwide.”
A hidden climate threat?
The study brings together scientists from China, Hong Kong, Pakistan, and the UAE, in research published under the title “Microplastics and Global Warming: A Hidden Climate Threat Uncovered in a New Perspective.” The paper offers a scoping review that maps the nature, range, and extent of existing research on the topic. By identifying gaps in the literature, they claim to uncover a hidden greenhouse effect rarely highlighted before.
“Oceans are Earth’s largest carbon sink,” said Dr Ihsanullah. “Microplastics are undermining this natural shield against climate change. Tackling plastic pollution is now part of the fight against global warming.”
The study emphasizes that “biological carbon pumping” – the ocean’s natural process that transfers carbon from the atmosphere into the deep sea layers – is the primary mechanism linking microplastics to global warming and climate change. “MPs interfere with this process by reducing phytoplankton photosynthesis and impairing zooplankton metabolism,” the authors note.
Another connection, the authors indicate, is related to the so-called plastisphere, referring to the communities of microbes in aquatic settings that form biofilms on surfaces. “The plastisphere is home to a variety of microorganisms, the majority of which are involved in biological processes like the nitrogen and carbon cycles.” Alarmingly, they maintain, microplastics also emit greenhouse gases during degradation, exacerbating their impact on climate systems.
Unappreciated connections
The study seeks to address knowledge gaps in the literature, which, according to the authors, has largely concentrated on identifying microplastics and developing cleanup strategies. They write, “The extent to which microplastics affect climate change, ocean health, and associated systems is currently unknown. This can be mostly because the issue is novel, intricate, and multifaceted. The significant ecological effects of plastic pollution in the oceans are well recognized, but its exact connections to these extensive environmental processes are not well understood.”
To bridge the gaps, the researchers explore the multifaceted effects of microplastics on ocean health and climate change, urging future studies to highlight the internal linkages between microplastics and climate change dynamics. Such dynamics, they argue, could foster a shift in “perspective in research and policymaking.”
The researchers urge policymakers not to underestimate the long-term impact of microplastics on ecosystems and human life, even if their current effects appear minimal. They caution that “while their (microplastics) current impacts may seem minor, their growing accumulation suggests future significance. The impact of MPs on ocean health, particularly concerning potential ocean warming and acidification, remains an area of concern.”
The authors call for an integrated approach, stressing that microplastic pollution and climate change cannot be addressed in isolation. “In this way, the effects of climate change could be lessened by taking appropriate action to slow down the production of microplastics,” they note.
Among other recommendations, the authors urge the UN to revisit its Sustainable Development Goals, pointing out that “plastics are currently represented by a single indicator, which may not adequately capture the widespread risks posed by microplastics across diverse ecological systems.”
