The lighthouse keeper's cat and invasive species

Fall of 1895. A small and unknown Pacific island will be the scene of one of the greatest ecological collapses described by science... the lighthouse keeper's cat and the sudden extinction of a species. But how did it happen?

Imagine a middle-aged man, David Lyall, assigned by the British Navy to the Stephens Island lighthouse, a rocky rock located between the two halves of New Zealand with heavy naval traffic. Good old Lyall, a grim man with few words, decided to take with him his pet, the little one Tibbles, a friendly cat that would help him to cope with the long nights in the lighthouse.

One fine morning, outside the lighthouse, Mr. Lyall found a dead bird, beautifully looking and totally unknown to him. Lyall, who was a lover of ornithology, decided to dissect the bird and send it to the Wellington Museum of Natural Sciences, where the renowned naturalist Lionel Walter Rothschild confirmed the discovery of the new species, which he named Lyall's Chochín (Xenicus lyalli) in honor of its discoverer, the lighthouse keeper of our history.

What happened is that the anecdote was going to turn into a tragedy. Day by day, more specimens of this bird appeared scattered around the lighthouse, on the door and on the steps of the staircase, until finally Mr. Lyall surprised his cat with one of these specimens in his mouth, still alive, and realized that it was the little kitten that caused the hunt.

The Stephens wren, a flightless nocturnal bird, devoid of defenses against predators that did not exist in its natural environment, became extinct in just 4 months, during the first winter that Mr. Lyall served as lighthouse keeper on the island.

The lighthouse keeper's cat had made the world's only, undoubtedly small, population of this bird disappear, a specimen of which science cannot know much about its biology, given the speed at which it became extinct.

This example, widely known in the world of ecology, became a paradigm of the impact that invasive species have on the native fauna or flora of a place and the serious imbalances they inflict on ecosystems. It is what is known in the natural sciences as the Frankenstein effect, in reference to the protagonist of Mary Shelley's famous novel, a term that refers to the 'well-intentioned' introduction or release of a living being, but whose unsuspected and unpredictable consequences can end in tragedy, just as in the story of the unforgettable monster.

Tibbles, the lighthouse keeper's cat, is just one more example of so many other cases of introduced and exotic species that today are serious problems for the conservation of biodiversity: catfish in the Ebro Delta, American mink in deciduous forests, American crab in rivers in Spain, zebra mussels in wetlands, Phytophthora in the oak forests, the Asiatic algae in the waters of the strait or the Egyptian weevil beetle, they make up an army of fungi, insects, birds, fish or mammals that have displaced native species, in cases, to the point of pushing them to extinction. In this regard, Spain is at the forefront of Europe in regulatory development to face the challenge of invasive species, approving an extensive catalog of species in 2011. These regulations include nearly 200 invasive species, some as harmful as the Asian wasp, water hyacinth, raccoon or Florida galapagos, which is causing our biodiversity to be among the most affected by this problem.

There will be those who think that life is like that. Human beings, in our incessant historical evolution, have been traveling from one place to another for millennia, carrying with us animals and plants that accompanied us to new destinations for economic or recreational purposes and that, used well intentionally for our interest, caused severe impacts on native ecosystems, a real problem that led to International Union for Conservation of Nature (IUCN) to declare invasive species as one of the serious threats to the conservation of biodiversity on a global scale.

How can we mitigate it? Well, without a doubt, with a mix of shared responsibility between citizens and administrations. On the one hand, avoiding the deliberate release of invasive species into the environment or the illegal possession of alcoholic species. On the other hand, public authorities must quickly assess and detect the presence of these species in natural ecosystems and act with control and/or elimination plans. A shared commitment that we must assume to avoid the extinction of new species, to preserve habitats, ecosystems and natural environments that today suffer the threats of a changing world where the vast majority of impacts come from the human species.