Giant tortoises reintroduced to Galapagos' Española Island are engineering the ecosystem by reducing trees, aiding cactus regeneration, and creating nesting grounds for the waved albatross.
A new study published in Conservation Letters by Tapia Aguilera & Gibbs provides evidence that reintroducing giant tortoises to Española Island in the Galapagos archipelago is transforming the island's plant communities.
They've since been a conservation success story, with over two thousand tortoises reared and released on the island, but what effect are they having on their habitat?
The study's findings suggest that trophic rewilding programs involving megaherbivores like tortoises could help restore critical ecosystem functions on islands where native species have been severely reduced.
"Tortoises consumed virtually every cladode that fell to the substrate. This would effectively eliminate vegetative reproduction in cactus Similarly, tortoises consumed almost all cactus fruits deposited, which would greatly expand the scope for seed dispersal away from the parent plant, where bird predation on seeds is most intense. We expect that seed dispersal by tortoises provides a critical vector for sexual reproduction in cacti, resulting in more cactus recruits in the larger landscape, whereas intense consumption of cactus parts by tortoises renders asexual reproduction by cactus inviable."
Tapia Aguilera & Gibbs conclude that, for Española Island, rewilding with Giant Tortoises has been a success, but caution against assuming that the circumstances here apply everywhere.