On the island of Aride (Seychelles), the reintroduction of just 10 Aldabra giant tortoises (Aldabrachelys gigantea) restored in six months ecological processes lost more than 180 years ago.
According to a study published in Restoration Ecology, the tortoises acted as true ecosystem engineers, reestablishing key functions such as:
- Seed dispersal of native species.
- Control of invasive plants.
- Nutrient recycling in the soil.
Immediate Results
In just two months, the tortoises dispersed more than 11,000 seeds, 89.5% of which were native species, and consumed 54 exotic plant species, limiting their spread.
These results exceed expectations and demonstrate that the reintroduction of a small number of individuals can have a massive ecological impact.
International Research
The project was led by the Doñana Biological Station (EBD), the National Museum of Natural Sciences (MNCN), the Royal Botanical Garden (RJB) of the CSIC, and the University of Exeter. Researchers combined field observations, fecal analysis, and DNA studies to accurately identify the species consumed by each specimen.
Diversity of Behaviors
One of the most relevant findings is that the results do not depend solely on the number of individuals, but on their behavioral patterns:
- Three tortoises dispersed more than 80% of the native seeds.
- Others excelled in controlling exotic plants or in nutrient recycling.
- Specimens like T08 showed outstanding performance in all three functions, while others, like T11, had low performance.
This functional diversity within the same species is crucial for the ecosystem’s resilience.
Implications for Conservation
The study suggests that restoration programs should include not only genetic diversity criteria but also behavioral and functional diversity. On small islands, critical functions may depend on a small number of individuals with distinct habits.
Furthermore, it is proposed to replicate this type of study in other places, such as the Galapagos archipelago (Ecuador), where giant tortoises fulfill similar ecological roles even though they are not evolutionarily related to those in Seychelles.
The experience in Aride demonstrates that the reintroduction of giant tortoises is an effective and economical strategy for restoring ecosystems. In just six months, ten individuals managed to recover ecological processes lost for nearly two centuries, confirming that nature can be reborn when its protagonists are returned.
