Rat-free islands could rebuild seabirds and reefs
Eradicating invasive rats and restoring native vegetation on Chagos islands could multiply seabirds ~18-fold and raise reef-fish biomass via seabird-derived nitrogen.
Source
Island restoration to rebuild seabird populations and amplify coral reef functioning
Study at a glance
- Design
- Computational / modelling — Habitat/abundance models predicting Chagos seabird recovery and reef-fish biomass under rat eradication
- N
- N=25 · Modeled eradication on 25 rat-infested islands (scenario study, not a field trial N)
- Population
- Lesser noddies, sooty terns, and red-footed boobies on Chagos Archipelago islands
- Outcome
- Predicted seabird abundance, nitrogen deposition, and reef-fish biomass under restoration
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Authors modeled breeding abundances of lesser noddies, sooty terns, and red-footed boobies across Chagos islands as a function of rats, island area, and native habitat, then predicted prey demand and seabird nitrogen reaching coral reefs under eradication and vegetation-restoration scenarios.
What they found
Rat presence suppressed breeding abundances. Eradication on 25 infested islands could raise those three species ~18-fold. Full eradication plus 75% native cover could lift reef-fish biomass ~52% (~50,000 extra tons), with nitrogen deposition rising from 78 toward 170 tons/year.
The limits
What it doesn't show
Predictions have wide uncertainty and assume prey and habitat can support restored densities; Diego Garcia and unmodeled islands, plus other invasive species, are not a full restoration trial.
Key terms
- Invasive black rats
- Rattus rattus introduced to Chagos islands, suppressing ground- and burrow-nesting seabirds.
- Cross-ecosystem subsidy
- Nutrients (especially nitrogen and phosphorus) moved by seabirds from pelagic prey onto islands and adjacent reefs.
- Chagos Archipelago
- Indian Ocean atoll group in a large marine protected area, with ~55 islands.
- Native vegetation restoration
- Replacing coconut-palm monocultures with native forest, savannah, or wetland cover that seabirds use for nesting.
- Hurdle model
- Two-part statistical model for zero-inflated seabird counts: probability of any breeders, then abundance if present.
Flashcards
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Quiz yourself
Primary invasive terrestrial threat in this study:
Common questions
What invasive mammal is the main terrestrial threat here?
Black rats (Rattus rattus).
How much could the three focal seabirds increase after rat eradication?
About 18-fold on the modeled infested islands.
What reef outcome is predicted with rats gone and 75% native cover?
About a 52% increase in shallow-reef fish biomass.
How much seabird nitrogen is deposited now?
About 78 tons per year on Chagos atoll islands.
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