Researchers in Spain have discovered that gulls visiting from Britain are transporting significant amounts of plastic waste from landfill sites to key wetland areas.
The threats posed by plastic pollution to marine environments have long been understood but this study sheds new light on the potential problems faced by freshwater sites. A paper recently published by the Doñana Biological Station of the Spanish Science Council (CSIC), and in collaboration with the British Trust for Ornithology (BTO), shows how birds feeding on landfill sites ingest significant amounts of plastic and other debris then later deposit these indigestible fragments while roosting at natural wetlands.
Gulls, like birds of prey and owls, regurgitate pellets often containing fish bones, feathers and other non-edible items. However, those birds feeding on open landfills often ingest plastic, glass and textiles along with human food waste. While we know that eating these pollutants can cause serious direct harm to birds' health, the newly published research shows that the problems could have far greater ecological impact than previously expected.
Wintering Lesser Black-backed Gulls are introducing plastics to protected wetlands after feeding at nearby landfill sites (Carl Bovis).
The study focused on Lesser Black-backed Gull, a common wintering bird in Andalucía in south-west Spain. The birds, which had been fitted with GPS tags at breeding sites in the UK including colonies in Cumbria and Pembrokeshire, were monitored as they fed at the landfills and moved to roost and bathe at the internationally important Laguna de Fuente de Piedra nature reserve in Málaga. Pellets disgorged by the gulls were collected at the lake and 86% of these were found to contain plastics. Researchers revealed that around 400 kg of plastic is deposited by gulls into the lake, which is famous for its colony of Greater Flamingos, each winter.
Once in the lake, these plastics have nowhere to go and will eventually break down into microplastics, causing possible long-term threats to other wildlife and the wider environment.
Senior author on the study, Professor Andy Green, said: "When we throw plastics away, some of them are likely to end up on being carried by birds into wetlands. It's another reason we need to reduce the amount of plastic waste we generate."
Throughout Europe, gulls feed widely on landfills and other waste sites, before heading to roost at wetlands, lakes and other freshwater locations.
Dr Chris Thaxter, Senior Research Ecologist with the BTO said: "This study suggests that the translocation of harmful plastics could be more widespread and problematic than we'd assumed. Gulls are highly mobile and act as highly efficient biovectors, transporting these pollutants considerable distances, posing yet more threats to important wetland habitats across the globe."
Reference
Martín-Vélez, V, Cano-Povedano, J, and 11 others. 2024. Leakage of plastics and other debris from landfills to a highly protected lake by wintering gulls. Waste Management 177: 13-23. DOI: https://doi.org/10.1016/j.wasman.2024.01.034
