Plastic Pollution Found in Insects at the Base of Land Food Chains

Plastic pollution is now contaminating land-based insects at the foundation of food webs, raising new concerns about long-term impacts on wildlife, according to a study by the Universities of Sussex and Exeter.

Researchers found plastic fragments in the stomachs of beetles, slugs, snails, and earthworms—species that are crucial to ecosystems. These pollutants are being passed up the food chain to birds, mammals, and reptiles.

The study, the most extensive of its kind, examined over 580 invertebrates from 51 sites across Sussex. Microplastics were present in nearly 12% of samples, with earthworms showing the highest contamination rate (30%), followed by slugs and snails (24%).

Polyester, often shed from clothing, was the most common type of plastic detected.

Professor Fiona Mathews from the University of Sussex said microplastics are now “ubiquitous at every level of the food web.” A food web refers to the network of interconnected food chains within an ecosystem.

Lead researcher Emily Thrift described the findings as “surprising and deeply concerning.”

“This is the first study to find plastics consistently turning up across an entire community of land invertebrates,” she said.

“Similar plastic types have previously been found in hedgehog faeces and appear to be entering the diet of birds, mammals and reptiles via their invertebrate prey.”

The team warned that plastic pollution should no longer be viewed solely as a marine issue.

Decomposers and herbivores like worms and slugs were the most contaminated, but carnivorous insects such as ladybirds also showed traces of plastic—likely consumed through their prey.

The chemicals released by degrading plastics in soil can harm biodiversity. Previous studies link plastic ingestion to stunted growth, organ damage, and reduced fertility in animals.

Co-author of the study Prof Tamara Galloway, from 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 Mathews said the focus has often been on plastics in “visible litter” but added the findings “suggest multiple hidden sources – from clothing fibres to paint particles”.

“There is now an urgent need to understand how different types of plastics are affecting ecosystems, and to take steps to reduce their release into the environment,” she said,

Covering six invertebrate groups and four levels of the food chain, the research underscores the need for stronger environmental monitoring and urgent action to reduce plastic pollution across terrestrial ecosystems.

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