Conservationists in Ibiza are warning the island’s native bright blue and green lizards are coming ever closer to extinction due to the mounting threats of invasive snakes and tourists’ litter.

The Ibiza wall lizard is endemic to Ibiza and neighbouring Formentera and is vital to the ecosystem of the islands, experts say, for pollinating plants and controlling pests.

Since the 2000s, the small, colourful reptiles, which are harmless to humans, have become endangered due to the proliferation of invasive snakes that first arrived in imported trees.

Conservation foundation IbizaPreservation says snakes are now present on up to 90% of the island, while the lizard population has decreased massively, believed to have disappeared from about 70%.

But there is also another issue affecting the species – litter left mainly by tourists at beauty spots.

Dean Gallagher, a snake catcher on the island, says he is constantly finding the bodies of dead lizards stuck inside discarded bottles and cans at Es Savinar, a southerly viewpoint where people often gather for sunset.

“I’m finding these lizards trapped in cans and bottles,” he tells Sky News. “Once they get inside their feet get wet from the drink inside, the beer or the Red Bull, and they can’t get out. Sun comes up, heats up the bottle, the can, and just fries a lizard inside. It’s absolutely devastating.”

Tourism accounts for about 84% of Ibiza’s economy and is vital for the island, with tourist spending reaching 4.3bn euros in 2024, according to the Balearic Institute of Statistics (IBESTAT) – an increase of 62% since 2016. The number of tourists reached a record high of more than 3.7m for Ibiza and neighbouring Formentera in 2023 – an increase of almost 25% since 2016.

The land Dean looks after at Es Savinar is private, he says, but people ignore signs and fences which were replaced at the beginning of the summer.

“We do rubbish collections probably once or twice a week,” he says. “We clear the whole area of bottles and cans then the next time, we go back and there’s even more.

“Bottles can cause bush fires. The forests are really dry at the moment, just one spark can set this place alight. And [litter] is also killing our lizards. They’re marvellous, beautiful creatures, they’re not aggressive and they keep the bugs away. The ecological value is really important.”

Dean lives near Santa Eulalia, where he says numbers are scarce. “Lots of parts of the north of the island now, they’ve completely diminished and it’s very sad,” he adds.

“And the very southwest corner of the island where this viewpoint is, this is the last place where they are in stable numbers. But the excessive rubbish, tourism, snakes, are gonna wipe them out completely.”

Visual surveys of areas of Ses Salines Natural Park by environmental association GEN-GOB have found the population there has decreased by between 70% and 90% since 2023.

GEN-GOB, Friends Of The Earth Ibiza and IbizaPreservation are among several organisations that have been working to save the species in recent years.

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Is Ibiza at breaking point?

Jordi Serapio, coordinator of Protegim Ses Sargantanes, IbizaPreservation’s lizard protection project, says abandoned bottles and cans are “deadly traps” for the animals.

And snake numbers continue to grow and expand toward territories where lizards still remain, he adds. The most common snake on the island – and the biggest danger to lizards – is the horseshoe whip snake, but other types have been spotted.

“It has followed a northeast to southwest expansion,” he says. “The highest snake densities are observed in what they have called the ‘invasion front’ – this is known precisely thanks to trapping.

“In contrast, in areas where lizards have already become extinct, there appears to be a much lower density of snakes.”

So the more food available for the snakes, the higher the numbers.

“This is something common in most biological invasions, which end up regulating themselves naturally,” Jordi says. “The unknown in this case is whether some lizard populations will manage to survive and adapt. Although everything seems to indicate that they won’t.”

He also highlights another problem – predation by both feral and domestic cats – which he says is a growing threat.

“In the current context of the species’ extinction, any additional pressure worsens the situation.”