Restoration through management: recovery of the endemic Scalesia forest in Galapagos
Island forests are becoming increasingly fragmented and colonized by invasive species, and the unique Scalesia forest in the Galapagos Islands is no exception. This forest has been reduced to fragments due to land use changes in the past, which are now increasingly invaded by introduced plants.
A 10-year vegetation monitoring program was conducted on Santa Cruz Island in the invaded area and in a control area, where invaders were being removed continuously. The impacts of invasive plant species were annually assessed, as well as the effects of the removal of these on cover, composition and diversity of the resident plant community.
Heinke Jäger and Miriam San José
Charles Darwin Research Station, Charles Darwin Foundation, Santa Cruz, Galapagos, Ecuador
Key findings include:
The three invasive plant species (Rubus niveus, Cestrum auriculatum, and Tradescantia fluminensis) had a significant negative impact on Scalesia pedunculata, the formerly dominant species of this forest. The additive effects of multiple invaders exacerbated the decline of this species, contributing to habitat degradation.
In removal plots, species composition shifted towards a greater presence of endemic plant species, including S. pedunculata.
Natural recruitment of S. pedunculata occurred only in removal plots, highlighting the necessity of management interventions for its regeneration.
All plots experienced an average decrease of 71% of adult S. pedunculata trees, with a significantly larger decrease in the invaded plots, demonstrating the unsustainable trajectory of these habitats under invasion.
If current trends continue and invasive species are not controlled on a larger scale, S. pedunculata faces local extinction on Santa Cruz Island within the next two decades.
Conservation Implications:
Large-scale and sustained removal of invasive plants is critical to prevent further loss of S. pedunculata and to promote the recovery of endemic-dominated plant communities.
Continued long-term monitoring will be essential to evaluate the success of removal efforts and adapt strategies as needed.
Efforts should integrate invasive species control with habitat restoration to bolster the resilience of the unique Scalesia forest ecosystem.
Photo above: Tree Scalesia (Scalesia pedunculata) by Haplochromis, CC BY-SA 3.0 (Created 1 August 2008, Uploaded 13 August 2008)
INVASIONS BULLETIN
Management Stories
This case exemplifies the broader challenge of balancing biodiversity conservation with invasive species management. By combining long-term monitoring with targeted management, this study could serve as a model for addressing plant invasions on islands, where endemic species are especially vulnerable to ecological disruptions (Jäger et al. 2024, Front. For. Glob. Change).