The global plastic waste trade contributes to coastal litter in importing countries, study shows

University of Illinois College of Agricultural, Consumer and Environmental Sciences

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URBANA, Ill. – The ubiquitous plastic beverage bottle makes up about half of plastic waste collected for recycling in the U.S. Most recycled plastic is processed domestically, but a portion is traded overseas. A new study from the University of Illinois Urbana-Champaign draws on citizen science data to investigate how the global plastic waste trade contributes to litter along coastlines and waterways in importing countries.

“There has been a lot of news coverage about the plastic waste trade. The concern is that exporting waste to another country creates opportunities for that waste to escape into the environment during transportation and storage. We wanted to see if plastic waste imports lead to higher amounts of plastic litter found in coastal areas,” said Becca Taylor, assistant professor in the Department of Agricultural and Consumer Economics, part of the College of Agricultural, Consumer and Environmental Sciences at U. of I. 

Plastic waste is an internationally traded commodity, which can be recycled into reusable materials, whereas plastic litter is the pollution that results from untreated waste.

“Overall, we find that a 10% increase in the amount of plastic waste a country imports is associated with a 0.6% increase in the amount of littered plastic bottles collected from coastal areas,” she said. 

This may not sound like much but it adds up quickly. While only about 2% of plastic waste is traded globally, it is a substantial amount considering the huge growth in plastic production over the past 30 years. International trade of plastic waste reached its peak in 2014 with 16 million metric tons (about 35 billion pounds). Furthermore, the waste trade moves primarily from the global North to the global South, leading to concerns about “pollution havens,” where countries with low environmental regulations and inefficient waste management systems are more likely to attract polluting industries.

To study their question, the researchers turned to an unconventional source: citizen science — that is, data collected by ordinary people around the world.

The Ocean Conservancy, a non-government environmental advocacy organization, leads an annual global beach clean-up event. Volunteers are trained to collect and document all coastal litter in designated areas. The data are aggregated to the country level and made publicly available.

Taylor and her colleagues obtained data for 90 countries from 2003 to 2022. They focused on plastic bottles because they are a recycled commodity, unlike other common types of waste such as cigarette butts and food wrappers.

The researchers used the United Nations global trade database to measure plastic waste imports per country and year. They also drew on existing academic research to evaluate plastic waste mismanagement rates by country.  The authors find that a doubling of the amount of plastic waste a country imports is associated with a 6% increase in the number of littered bottles collected. Furthermore, countries that struggled with poor waste management systems had a proportionally higher increase in litter.

The authors also examine recent changes in the international waste trade, which shifted considerably in 2017, when China banned plastic waste imports. China had been the primary market for plastic waste, and its policy change caused total plastic imports to decrease by 73%. 

Some of the waste found its way to other countries, such as Thailand and Malaysia, where plastic imports increased significantly after China’s ban. The researchers looked at what happened to litter in those countries, finding that a 1000-ton increase in plastic waste imports from 2016 to 2017 was associated with a 0.7% increase in littered plastic bottles. 

However, countries that initially saw an increase in their plastic imports after China's policy changed later implemented their own waste import bans. Another policy change came in 2019 when plastic was added to the Basel Convention, a global agreement on the trade of hazardous waste. Consequently, countries that have ratified the convention (the U.S. is not among them) agree to follow certain guidelines for trade.

“In summary, we do find that plastic waste imports lead to increased coastal litter, and policies that aim to regulate or ensure importing industries are following best practices will have an impact. But cutting down on trade is not sufficient to eliminate litter along the coastlines. We also need to consider waste management practices more broadly and provide assistance to countries with less advanced waste management systems,” Taylor concluded. 

The paper, “Plastic waste imports & coastal litter: Evidence from citizen science data,” is published in Ecological Economics [10.1016/j.ecolecon.2025.108848]. 

Research in the College of ACES is made possible in part by Hatch funding from USDA’s National Institute of Food and Agriculture.

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Journal

Ecological Economics

DOI

10.1016/j.ecolecon.2025.108848 

Article Title

Plastic waste imports & coastal litter: Evidence from citizen science data

 

Research reveals new hybrid state of matter where solids meet liquids

University of Nottingham

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video: 

Theoretical modelling explores the movement of atoms within a liquid nanodroplet of platinum that is confined inside a defect in a carbon support. The colours represent the mobility of the atoms: platinum atoms at the edges are much less mobile and create an atomic corral around the more mobile atoms located in the centre.

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Credit: University of Nottingham

Researchers have discovered that not all atoms in a liquid are in motion and that some remain stationary regardless of the temperature, significantly impacting the solidification process, including the formation of an unusual state of matter—a corralled supercooled liquid.  

The formation of solids is essential in various natural processes, including mineralisation, ice formation, and the folding of protein fibrils. It also plays a significant role in technological applications such as pharmacy and industries that use metals, such as aviation, construction, and electronics.

Scientists from the University of Nottingham and the University of Ulm in Germany have used transmission electron microscopy to image the solidification processes of molten metal nano-droplets. This study has been published today in ACS Nano.

Professor Andrei Khlobystov, who led the team, said, ‘When we consider matter, we typically think of three states: gas, liquid, and solid. While the behaviour of atoms in gases and solids is easier to understand and describe, liquids remain more mysterious.’

Atoms in liquids move in a complex way, resembling a jostling crowd of people. They constantly and rapidly pass by each other while still interacting with one another. Studying the behaviour of atoms in liquids can be challenging, especially during the critical stage when the liquid starts to solidify. This stage is crucial because it determines the structure and many of the material's functional properties.

Dr Christopher Leist, who performed transmission electron microscopy experiments at Ulm using the unique low-voltage SALVE instrument, said, ‘We began by melting metal nanoparticles, such as platinum, gold, and palladium, deposited on an atomically thin support—graphene. We used graphene as a sort of hob for this process to heat the particles, and as they melted, their atoms began to move rapidly, as expected. However, to our surprise, we found that some atoms remained stationary.’ 

The researchers found that stationary atoms are strongly bonded to the support material at locations of point defects, even at very high temperatures. They were able to increase the number of defects by focusing the electron beam and so control the number of stationary atoms within the liquid.

Professor Ute Kaiser, who estabilished the SALVE centre at Ulm University, said, ‘Our experiments have surprised us as we directly observe the wave-particle duality of electrons in the electron beam. We visualise the material using electrons as waves. At the same time, electrons behave like particles, delivering discrete bursts of momentum that can either move or, surprisingly, even fix atoms at the edge of a liquid metal. This remarkable observation has allowed us to discover a new phase of matter.’

The team previously reported films of chemical reactions involving individual molecules, including the first instance of a chemical bond breaking and forming in real time. Their method enables the observation of chemistry at the atomic level.

In this study, the researchers found that stationary atoms have an influence on the solidification process. When there is a small number of them, a crystal forms directly from the liquid and continues to grow until the entire particle solidifies. However, when the number of stationary atoms is high, the solidification process is significantly disrupted, preventing any crystal from forming.

Professor Andrei Khlobystov from the University of Nottingham said ‘The effect is particularly striking when stationary atoms create a ring that surrounds the liquid. Once the liquid is trapped in this atomic corral, it can remain in a liquid state even at temperatures significantly below its freezing point, which for platinum can be as low as 350 degrees Celsius—that is more than 1,000 degrees below what is typically expected.’

Below a certain temperature, the corralled liquid solidifies, not into a crystalline form but as an amorphous solid. This amorphous form of metal is highly unstable, maintained only by the confinement of stationary atoms. When the confinement is disrupted, the tension is released, allowing the metal to transform into its normal crystalline structure. 

Dr Jesum Alves Fernandes, expert in catalysis at the University of Nottingham, said, ‘The discovery of a new hybrid state of metal is significant. Since platinum on carbon is one of the most widely used catalysts globally, finding a confined liquid state with non-classical phase behaviour could change our understanding of how catalysts work. This advancement may lead to the design of self-cleaning catalysts with improved activity and longevity.’

So far, corralling at the nanoscale has been achieved only for photons and electrons; this work is the first time that atoms have been corralled. Professor Andrei Khlobystov said, ‘Our achievement may herald a new form of matter combining characteristics of solids and liquids in the same material.’

The researchers hope that manipulation of the positions of pinned atoms on the surface may create more extended and complex corral shapes. This could pave the way for more efficient use of rare metals in clean technologies, such as energy conversion and storage.

This work is funded by the EPSRC Programme Grant ‘Metal atoms on surfaces and interfaces (MASI) for sustainable future’ www.masi.ac.uk addressing the challenges of sustainable use of rare elements in the future.

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Journal

ACS Nano

DOI

10.1021/acsnano.5c08201. 

Article Publication Date

9-Dec-2025

 

Learn the surprising culprit limiting the abundance of Earth’s largest land animals

Northern Arizona University

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Humans live in a world abundant in salt, but this everyday seasoning is a luxury for wild herbivores, and it’s far from clear how these animals get enough.   

A new study published today in Nature Ecology and Evolution and authored by Northern Arizona University researchers and collaborators found the density and distribution of Earth’s largest land animals, including elephants, giraffes and rhinos, appear to be limited by this kitchen essential. There are only a few areas in the world where these large animals can get enough sodium from the local flora to survive. 

“In Africa, sodium availability varies over a thousandfold in plants,” said Andrew Abraham, lead author of the study, a research associate at City University of New York and NAU alumnus. “This means that in many areas, wild herbivores simply cannot get enough salt in their diet.”  

This is true to some extent for all herbivores—most plants don’t need salt and often contain trace amounts of it—but it’s especially pronounced for megaherbivores. Previous research had suggested that sodium deficiency increases with body size. Using a totally separate methodology, this study reached the same conclusion. 

Mapping the missing megaherbivores 

The authors combined their high-resolution maps of plant sodium with databases of animal dung and density measurements. Dung can tell scientists a lot about animals, including whether they’re getting enough salt. They connected areas with salt limitation to lower numbers of larger herbivores.  

It’s not just about ability to survive, though. Salt limitation explains several interesting behaviors exhibited by wild animals.  

“In Kenya, elephants enter caves to consume the sodium-rich rocks and in the Congo rainforest, they dig for salt in riverbeds,” Abraham said. “Gorillas are known to fight for the saltiest foods, while rhinos, wildebeest and zebra often gather at salt pans from the Kalahari Desert to the Maasai Mara.”  

This study also offers a new explanation for the “missing” megaherbivores.  

“West Africa is a very productive region, but there aren’t many megaherbivores there,” said Chris Doughty, a professor of ecoinformatics at NAU. “We think that a lack of sodium, likely combined with other factors such as overhunting and soil infertility, plays an important role in limiting their numbers.”  

This research raises a number of conservation concerns. Many protected areas are located in low-sodium environments, and humans have created artificial sodium hotspots through various activities like borehole pumping and road salting.  

“If animals can’t get enough sodium in their natural habitats, they may come into conflict with people on their quest to satisfy their salt hunger,” Abraham said.   

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Journal

Nature Ecology & Evolution

DOI

10.1038/s41559-025-02917-y 

Article Title

Sodium constraints on megaherbivore communities in Africa

Article Publication Date

9-Dec-2025

Elephants, giraffes and rhinos go where the salt is

University of Zurich

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Herbivores require a steady intake of sodium to keep their metabolism running smoothly. This is why farm animals have long been given salt or mineral licks. Animals in the wild, however, need to get their salt from sources in their habitats. In some areas, plants and other natural sources of salt provide sufficient sodium, while in others sodium levels are scarce. These differences can influence where certain species settle or how far they will migrate to find natural salt licks.

A new study conducted in collaboration with the University of Zurich now shows that in many places the largest herbivores in the wild – elephants, giraffes and rhinos – have limited access to sodium. The researchers combined high-resolution maps of plant sodium with data on the animals’ population density and with results of fecal analyses. Since sodium deficiency is directly detectable in the feces, they were able to draw conclusions about the species’ actual sodium intake.

The larger the body, the greater the risk

“Plant sodium availability varies by a factor of 1,000 across sub-Saharan Africa,” says Marcus Clauss, co-director at the University Animal Hospital at UZH and co-author of the study. “In some areas, wild herbivores are simply unable to get enough salt through their food.”

However, not all herbivores are equally affected. The researchers found that sodium scarcity is particularly common among larger-bodied species, or megaherbivores. Their study confirms previous findings that the risk of sodium scarcity increases with body size.

Sodium shortage affects habitat selection

The study also explains certain wildlife behaviors. “In Kenya, for example, elephants enter caves to reach sodium-rich rock, while in the Congo they dig for salt in riverbeds. And this behavior isn’t limited to elephants. Gorillas fight over particularly salty foods, and rhinos, wildebeest and zebras often congregate at salt pans in the Kalahari Desert,” says first author Andrew Abraham of Northern Arizona University.

The study also provides a new explanation for the scarcity of megaherbivores in West Africa, a region rich in vegetation and species but where megaherbivore numbers are low. The researchers suspect that sodium deficiency plays a central role in the low numbers observed, likely in combination with other factors such as overhunting or poor soil fertility.

Potential conflicts

The researchers also point to key issues for nature conservation. “In areas populated by humans, artificial sodium hotspots are created by boreholes or – in northern parts of the world – by road salting. However, since many protected areas are located in regions that are low in sodium, animals that travel long distances in search of salt could come into conflict with humans more frequently in the future,” explains Clauss.

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Journal

Nature Ecology & Evolution

DOI

10.1038/s41559-025-02917-y 

Method of Research

Meta-analysis

Subject of Research

Animals

Article Title

Sodium constraints on megaherbivore communities in Africa, Nature Ecology & Evolution

Article Publication Date

9-Dec-2025