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Plastic pollution is harming invertebrates at the bottom of the food chain, including beetles, slugs, snails and earthworms, according to a new study by the University of Sussex and the University of Exeter. More than one in ten samples had fragments of plastic in their stomach, and harmful chemicals are being passed onto larger animals who feed on them. 

Researchers analysed more than 580 samples from 51 sites across Sussex. Microplastics were found in nearly 12%, with the highest levels recorded in earthworms (30%) and slugs and snails (24%). Polyester was the most common type of plastic found in the invertebrates tested, likely from clothing threads.  

The researchers say these findings show plastic pollution is not just a marine issue, and the chemicals released as plastics break down are equally dangerous when present in soil. Previous studies have shown ingesting plastic can lead to stunted growth, reduced fertility and changes in liver, kidney, and stomach function in various species, raising alarm among conservationists.

While herbivores and organisms that feed on decaying plant matter had the highest contamination rates, carnivorous species such as ladybirds were also affected, often ingesting larger fragments of plastic. The findings raise new concerns about the long-term effects of plastic contamination and its impact on biodiversity. 

“We were surprised by just how widespread this plastic contamination is,” said lead author Emily Thrift, Ecology Doctoral Tutor at the University of Sussex. “This is the first study to find plastics consistently turning up across an entire community of land invertebrates. Similar plastic types were found in hedgehog faeces in our earlier research and they seem to be entering the diet of birds, mammals, and reptiles via their invertebrate prey.” 

Co-author Prof Tamara Galloway of the University of Exeter said: “To reduce the uptake of microplastics into the food web we first have to understand how it is getting there. Emily’s results are a crucial first step to understanding this process and its consequences for wildlife.”

Prof Fiona Mathews, Environmental Biologist at the University of Sussex added: “Microplastics are now ubiquitous at every level of the food web. Attention is currently focused on litter as the main source of contamination, but these findings suggest multiple sources ranging from clothing to paint. There is now an urgent need to understand how different plastics are damaging ecosystems and to cut the volume entering the environment.” 

This is the most comprehensive study of its kind, spanning four levels of the food chain and six invertebrate groups to assess the full extent of plastic contamination in a land-based ecosystem. 

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