PROJECT: Española Survey and Monitoring: The Response of Giant Tortoises,
Tree Cacti, and Waved Albatross to manipulation of woody
vegetation on Española Island, Galapagos
PARTNERS: Research Foundation of SUNY, Galapagos National Park Service
STATUS: Funded in 2011 and currently being implemented
Española Island in the Galapagos Archipelago is home to three globally endangered, interacting species: the Waved Albatross (the world’s only tropical albatross), a morphologically and genetically distinct lineage of Giant Tortoise, and a large-seeded, arboreal Prickly Pear Cactus.
The Galapagos Conservancy-supported Española survey in May–June 2010 focused on the interactions among these species. Results of that survey show that the native woody vegetation has reached extremely dense levels not seen in the last 1000 years. This incursion by woody plants on the island is likely the legacy of 73 years (1905 to 1978) of excessive goat densities, which may have fundamentally altered competitive relationships between woody and herbaceous plants in large part through changes in soil conditions that now favor woody plants.
Key findings of the 2010 survey include:
- Woody plant cover is extensive on Española to a degree anomalous in the island’s vegetation history
- Woody plant cover is expanding and likely doing so to the long-term detriment of tortoises, cactus, and inland nesting albatross
- About half of all tortoises ever repatriated are alive but are not substantially “engineering” the island’s vegetation in the sense of hindering incursion of woody vegetation or affecting cactus populations
- Cactus remains an important, yet scarce, resource for tortoises and is not competing well with woody plants
- Española supports an inland nesting population of Waved Albatross that likely represents a substantial component of the species’ global population and that should become the focus of intensive monitoring and a better assessment of its size and distribution
This research clearly indicates that there is an ecological imbalance on Española. However, how to proceed with conservation management is less clear. Key staff in the GNPS have concurred that in the near-term, small-scale manipulations of woody cover could greatly clarify two important, remaining “unknowns”; 1) the likely response of Española’s flagship species to removal of woody plants; and 2) costs and logistics associated with a large-scale manipulation of the woody cover on Española (a possible future course of action).
This project will carry out ecological monitoring as part of a joint management action/scientific experiment associated with creation of small-scale disturbances of woody vegetation on Española planned by the GNPS in late 2012. Other components of the work will clarify the history of the vegetation and albatross occupancy on the southern side of the island as well as complete a definitive assessment of inland nesting populations of waved albatross. This joint science/management effort will generate critical information to provide the GNPS with the necessary foundation for final decision-making about how best to proceed with island-wide conservation management. The project also involves substantial training opportunities for GNPS rangers (e.g., unmanned aerial vehicle or UAV operation) as well as technology transfer for other applications in the Park.
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