Sombrero island has been so degraded by human activity that it no longer looks like a hat to approaching sailors. Once a small mound covered in forest, and with its own species of giant tortoise, the 94-acre outpost has been transformed into a barren moonscape by guano mining, invasive mice and hurricanes.
The island, part of Anguilla that marks the entrance from the Atlantic Ocean to the Caribbean sea, was even considered at one point as a launchpad for commercial satellites by Texan billionaire Andrew Beal in the late 90s. Now, surges from Atlantic hurricanes – turbocharged by climate change – grow so high that they inundate its 40ft limestone cliffs, washing away seabird eggs and lizards.
Still, life clings on, and Sombrero Island’s fortunes may be about to change after decades of ecological decline.
In July 2021, the last invasive mice were killed as part of efforts to restore wildlife on the island, which largely congregates around an abandoned lighthouse. A year later, the rodents have not reappeared, and the wildlife, which includes species found nowhere else on Earth, is making a comeback.
“The Sombrero ground lizard has already increased a lot. There were fewer than 100 in 2018, and the last count had 884 individuals,” says Jenny Daltry, Caribbean director with Re:wild and Fauna & Flora International, who was part of the mouse eradication project at the internationally important bird breeding site.
“I’m quite optimistic we’ll see a lot of improvement.”
Despite its humble size, Sombrero is part of a trend in one of conservation’s biggest success stories. According to a new study published this week, removing goats, rats, mice, dogs and other invasive species from islands has had an 88% success rate since 1872, resulting in spectacular transformations in degraded atolls and archipelagos.
The size, complexity and ambition of invasive species removal is also growing, according to the study, spurred by island states like New Zealand that is aiming to clear all invasive mammals by the middle of the century.
“Sombrero’s recovery is probably going to be slow because it’s limestone, it’s arid and has very little soil left,” says Daltry, who also helped with the restoration of Redonda island, farther south on the Leeward Islands arc, and dozens of other islands.
“It will take time for the vegetation and soil to rebuild so that it can support trees and bushes. In 10 years’ time, there’s a chance it will have full green cover, but it will take longer to get back to the kinds of forest the giant tortoises would have recognized.”
The success of invasive species clearance projects on islands has prompted conservationists to scale up their ambitions. This promises disproportionate benefits for Earth’s biodiversity, with islands like Madagascar, the Galápagos and Borneo home to huge numbers of endemic species. Daltry has her eye on Jamaica’s Goat Islands, and larger areas on populated islands.
Anguilla has plans to fence off a five hectare (12 acre) area and clear invasive species on the mainland in Fountain Cave national park. The country successfully cleared Dog Island and its satellites in 2012, boosting numbers of sooty terns from 113,000 to more than 300,000 nesting pairs, and benefiting lizards and endangered green and hawksbill turtles, both threatened with extinction.
“[Clearing Fountain Cave national park] means we would be able to reintroduce native and potentially endangered wildlife back into that area, so it works as a conservation sanctuary,” says Farah Mukhida, executive director of Anguilla National Trust, who was part of the team that helped clear Sombrero Island.
“Most of the work has focused on offshore cays, and not many people are able to go there. By doing this on the mainland, we’re creating a nice conservation area for biodiversity, and we are also able to show residents what is possible when you remove invasive species,” she says.