Experts issue warning as invasive snakes torment island creatures: 'They advance as if they were on the front of a battle zone'

Invasive snakes are spreading throughout Ibiza, Formentera, and the surrounding islets, according to El País. Several species of native creatures have already gone locally extinct.

What's happening?

In 2003, snakes were found on a shipment of ornamental trees bound for Ibiza. Now, over 20 years later, they're wreaking havoc.

"They advance as if they were on the front of a battle zone," Oriol Lapiedra, a researcher studying the snakes, told El País. "You have to imagine the snakes as if they were an actual wave, devouring what they find."

Last year, over 3,000 snakes were found, increasing a thousandfold from 2023. The snakes have even managed to swim to the islets outside Ibiza, ensuring that nowhere is safe for their native prey. 

Experts informed El País that field mice, shrews, and geckos have become locally extinct as a direct result of their spread. And another animal might be next in line for the chopping block.

The Ibiza wall lizard is a crucial pollinator for its ecosystem. Because of the snakes, a majority of the island is now uninhabitable for the species. As the former head of the food chain, it hasn't adapted to having a predator.

Why do Ibiza's invasive snakes matter?

Their spread is indicative of a larger pattern worldwide. A 2023 United Nations report found that human activity has introduced over 37,000 invasive species into non-native environments, costing the global economy over $423 billion. 

Zebra mussels, for instance, have invaded the Colorado River, threatening local marine life and water supplies. And the ash borer beetle has colonized most of the United States, leaving millions of dead trees in its wake.

Specifically, these snakes' invasion of Ibiza has disrupted its delicate ecosystem. Lapiedra told El País that they pose an even greater threat to the islets, where the ecosystems are smaller. It's a conservation nightmare.

What's being done about it?

Instead of focusing on eradication — the snakes are too widespread for that option to be viable — scientists are trying to find ways for the snakes and the Ibiza wall lizards to coexist peacefully. According to El País, Spain's Ministry of Agriculture, Fisheries, and the Natural Environment and the Barcelona Zoo are launching a breeding program for the lizard species. 

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It could keep the species alive while researchers work to create safe havens for the existing lizards. If the population remains stable, Ibiza wall lizards may be able to develop defense mechanisms against the snakes, restoring some balance.

To fight this battle at home and help your local ecosystem thrive, consider rewilding your yard with native plant species. 

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