In 1940, a creature invaded an island in the United States and ate everything. The two species most feared by humans today coexist alone

History is full of island stories that show us that, although nature is fascinating, two and two do not always equal four, and many species are so incompatible that they cause others to disappear. For example, the history of Japan is a perfect example, although humans were the real culprits there. On other occasions, as we are going to tell, “stowaways” enter the island without being noticed.

A devastated ecosystem. In the forests of the island of Guam, one of the fourteen unincorporated territories of the United States, a paradox exists: there are 40 times more spiders than in the forested areas of nearby Pacific islands, but their presence is not due to the habitat of the enclave’s core. . No, the spread of many species of spiders is due to the arrival of an unexpected creature in the 1940s.

Indeed, as we shall see, the island is caught in a cycle of ecological change, its landscape becoming a most disturbing spectacle, where native wildlife has been almost completely displaced by predatory invaders: the brown tree snake and that Giant spider population. Intruders have significantly altered Guam’s appearance, creating an unusual environment and irreversibly altering its biodiversity.

An accident. Haldre Rogers, an associate professor in the Department of Fish and Wildlife Conservation at Virginia Tech who has been studying the enclave’s ecology for 22 years, told the BBC, a scene he experienced on the island at a meeting five years ago. A pig was being roasted outside the premises when suddenly a surprise guest arrived. The pig has a brown appearance all around, shiny and scaly, with straight eyes and a wide mouth. The creature was tearing pieces of pig meat and swallowing them whole into its body.

That surprise “visitor” was a brown tree snake, an invader believed to have inadvertently arrived in Guam in the 1940s, possibly after burrowing into a cargo ship. Since then, the snakes have caused an unprecedented process of destruction among the island’s fauna. In just a few decades, these predators have exterminated almost all native bird species, which had no defense mechanisms against the arrival of these insatiable reptiles.

Without their presence, Guam’s forests have lost not only their song, but also an important ecological function: seed dispersal, which used to ensure the regeneration of its leafy trees.

Spider’s web. Furthermore, the absence of birds has given rise to another unique phenomenon: an explosion of spiders that has transformed the forest into a landscape full of webs stretching in all directions. Yes, it seems that the spiders have taken advantage of the lack of predators, and have proliferated to such an extent that they have covered the vegetation with wide and dense webs that hang like a veil over the forest.

In every clearing and in every corner of the island, spiders, especially spiders of the Argyrodes species, They have woven complex communal structures that are a clear expression of the ecosystem disruption quietly unfolding in Guam.

Forest structure in danger. There is no doubt that the extinction of the birds has changed the dynamics of the island’s forests. As we said, without birds spreading their seeds, many trees are unable to reproduce, and natural regeneration has begun to stop to such an extent that a real threat to the ecosystem is created.

The ground covered with dry leaves and fruits, which fall uneaten, represents the lack of new shoots that will occupy the space left by the fallen trees. In this eerie silence of the forest, the ecological structure changes in reflection of the impact that this unusual invasion of snakes is capable of producing.

No solution. Despite tireless efforts by researchers to control snake populations, measures ranging from the use of poisonous baits to the development of “snake-proof” climbing methods, have had limited success: such snakes number more than two million.

The brown tree snake has proven to be a formidable opponent: its adaptability and resistance to eradication methods have thwarted even the best-funded projects to date. There are some exceptions, there are some controlled areas, such as Andersen Air Base that have managed to limit their presence, but the majority of the island remains in the zone of this invasive species which one day came as an escape and killed almost all species. Destroyed.

uncertain future. With a forest that is losing its diversity and an imbalanced food web, the future of Guam is headed toward an irreversible change that is the subject of study and debate. The island that was once a vibrant and balanced ecosystem has become a natural laboratory where interactions between species have disintegrated, and new dynamics, controlled by invaders, have emerged in their place.

Ultimately, the fate of Guam raises many serious questions about the fragility of island ecosystems and the lasting impact of invasive species on these unique environments. To his dismay, Guam has become a grim testament to the power of invasive forces to redefine the boundaries of nature, leaving behind an unrecognizable ecosystem, defined by silence and a dense tangle of spider webs. .

Image | Animalia, Jonathan Miske

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