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For wildlife lovers, one of the highlights of a Galapagos holiday is the opportunity to encounter the iconic Galapagos Giant Tortoise. This massive terrestrial reptile is one of the most high-profile species of the archipelago and plays a vital role in its extremely biodiverse ecosystem. Recently, however, scientists researching the harmful spread of invasive plant species around the islands have discovered a disturbing possibility; the tortoises may potentially become part of the very problem that threatens their habitat. The Giant Tortoise's Role in Seed Dispersal The Giant Tortoises of the archipelago have been dubbed the "Galapagos Gardeners", for their ability to travel long distances and navigate thick vegetation in their search for food sources. This strength and stamina makes them a keystone species of the islands, responsible for the creation of the majority of the diverse habitat zones. Their astounding consumption of plant matter and long distance migratory habits directly contribute to seed dispersal. In fact, there are some native plant species that cannot germinate until they pass through the tortoise's digestive system. Spread of Invasive Plant Species The spread of invasive plant species is a major problem in maintaining the balance of the archipelago's delicate ecosystem; unfortunately, introduced species now outnumber the native ones. In terms of seed dispersal, the issue lies in the tortoise's lack of ability (or inclination) to distinguish between native and invasive species. Many of the introduced plant species provide excellent and very tempting food sources, including the passion fruit and the guava – both of which were brought to the islands by humans. Dispersal of Guava and Passion Fruit Seeds Currently these particular species thrive in the humid highlands of the archipelago, especially on the island of Santa Cruz. While the tortoises disperse large quantities of their seeds to the lowlands, at present they rarely germinate in those locations. However, scientists' concern is that with the potential of global warming looming over the planet, the negative impact of this dispersal of invasive species could be greatly increased. Using computer models to predict the results of climate change, scientists say that longer periods of hot weather and increased rainfall could transform the lowlands into a more humid habitat. This would allow these species to thrive and increase their geographical range in dramatic proportions. Preventative Measures While the effects of the predicted seed dispersal could be highly damaging for the islands in the long term, researchers and conservationists are taking measures to prevent the possibility. Although it appears complete eradication of the guava and passion fruit is impractical at this stage, the Giant Tortoise Movement Ecology Programme is focusing on research into the tortoise's migratory habits, with a view to strategising future conservation projects to prevent or reduce the dispersal of invasive species. Contribute to Conservation on a Galapagos Holiday For those who visit this unique region on a Galapagos holiday, simply taking the opportunity to learn more about the ecology of the archipelago is a great step towards helping to aid in its conservation. Raising the profile of this unique region by educating others on the present and potential issues it faces is vital to ensure its magnificent biodiversity is preserved for the future. Author Plate Marissa Ellis-Snow is a freelance nature writer with a special interest in the unique wildlife of the Galapagos Islands. Marissa chooses the expert-led Galapagos holiday itineraries organised by Naturetrek, which have brought her unforgettable sightings of a wide range of wildlife in one of the most spectacular regions on Earth.
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