Snakes, pirates and goat eradication: on the issue of invasives

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There are no snakes in the Galapagos. That was until one was found dead in the middle of the road on Santa Cruz island in February of this year. The snake, most likely brought to the island by ship, made its way 600 miles off the mainland, past security and quarantine and into the ecosystem. In the Galapagos, if you are anything other than endemic (exceptions made for international students studying abroad), you are an invasive and therefore a threat to the ecosystem.

The Galapagos are famous for having the most comprehensive policies and practices in the world to counter invasive species. Shipped goods go into quarantine. All luggage to the islands is scanned for invasives, sealed shut with industrial strength zip ties and sprayed with disinfectant. And yet, invasives continue to be an ongoing problem for the Galapagos. If these strict policies aren’t enough, perhaps it is time to reevaluate current practice and rethink strategies against invasives and even what it means to be an invasive.

The reality is that the Galapagos do not exist in a vacuum and haven’t for 400 years. In the 1600s the islands were used by pirates as a midway point in the Pacific. During this time pirates on trade routes introduced species such as pigs and goats to the islands. Even the H.M.S. Beagle was responsible for introducing livestock to the Galapagos.

Over the past 400 years the goat population has gone rampant, growing to about 80,000. The only mammals in the Galapagos are a few species of small rodents, fur seals and sea lions. Because there are no other competing large land mammals, the goats were able to multiply throughout many of the islands. The goats also leave “goat trails,” barren areas left after feeding, that cause erosion and affect many endemic species like the famed giant tortoises. The giant tortoises live in shaded areas, but when goats eat through the shade the tortoise habitat is destroyed.

Many attempts were made to keep the goat population at bay, but none worked until Project Isabella, otherwise known as Project Judas Goat. Conservationists in the Galapagos borrowed this innovative strategy after it successfully eradicated invasive goats in New Zealand. The strategy is fairly simple: train sterilized goats to find herds, then follow them using a GPS receiver to make the kill. Ten years and $6.1 million later, conservationists announced in 2006 that the goats on the islands of Pinta, Santiago and the northern portion of Isabella had been eradicated.

This tactic may be novel, but it does not end at eradication. Fighting invasives not only requires complete eradication, but the dedication of ongoing time and resources to make sure that not a single goat makes its way back to the islands. This goes for anything from goats to invasive raspberries that have been spread throughout the islands by the beak of the finch.

With globalization, the reality is that most places do not have the economic or political incentive that the Galapagos do to invest in this never ending battle against invasive species. The rational answer may be policy that aims to keep invasive populations to controlled amounts as opposed to plans for complete eradication.

Furthermore, thinking about the Galapagos’ famous past in relation to its present and future, the goal of eradicating invasive species in a way stands in conflict with evolution. According to Darwin’s theory of natural selection, invasive species are evolutionary successes for their ability to thrive in a multitude of ecosystems. Even the endemic species in the Galapagos successfully migrated and adapted to the islands.

At a certain level the history of the Galapagos isn’t a history of isolated evolution, it is a history of invasives. Perhaps embracing this history is the first step in rethinking conservation missions against invasives in the future.