Natural fibre alternatives: A hidden threat to earthworms

New research suggests that natural substitutes for plastic may be more damaging to nature than plastics themselves. Scientists from the University of Plymouth have shown that cellulose fibres present in the soil cause higher mortality in earthworms than polyester fibres.

In experiments conducted on earthworms, the impact of minute fibres released into the environment from both plastic items and materials made from biological sources was studied. It was found that at a high concentration of polyester fibres, 30% of the earthworms died after 72 hours.

In the presence of cellulose-based fibres—lyocell and viscose—the mortality rate increased to 60% and 80%, respectively. The research also indicates that viscose more significantly impaired earthworms' reproductive abilities than polyester. Earthworms placed in soil containing lyocell fibres showed reduced growth and behavioural changes, such as increased tunnelling speed, compared to exposure to other types of fibres.

The studies highlight the complexity of the plastic pollution issue and emphasize the need for thorough testing of new materials promoted as eco-friendly alternatives. Dr. Winnie Courtene-Jones, the main author of the publication in the journal "Environmental Science & Technology," points out that in 2022, more than 320,000 tonnes of biodegradable and biologically sourced fibres were produced worldwide.

"The research shows that a significant portion of it will end up in the environment. Our study demonstrated that biologically sourced fibres have a range of negative effects on earthworms—animals crucial for ecosystem functioning," comments Courtene-Jones.

The new publication was released shortly before a meeting of world leaders in Busan, South Korea, where the final round of negotiations for a possible global treaty on plastic will take place. Professor Richard Thompson, one of the main authors of the study and head of the International Marine Litter Research Unit at the University of Plymouth, will participate in these discussions.

He points out that combating plastic pollution requires reducing the amount of plastic used and produced, in addition to recycling and reusing. Although there is a growing demand for finding alternatives to plastics, the latest research shows that they need to be thoroughly examined to understand the consequences of their proliferation.

Professor Richard Thompson expresses strong confidence that the plastic pollution crisis is solvable, emphasizing that independent scientific evidence is essential to prevent unintended consequences when exploring new solutions.

Previous studies published earlier this year showed that exposure to materials used in biodegradable tea bags could increase earthworm population mortality by up to 15% and negatively impact their reproduction.