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
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Inspect source passages
Rat-free islands could rebuild seabirds and reefs
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Rats gone plus 75% native cover could support a 52% increase in reef fish biomass (50,000 tons more).
If rats were predicted to be eradicated and 75% native vegetation cover was restored throughout the Chagos Archipelago, the shallow coral reef area of the Archipelago could support a 52% increase in reef fish biomass, resulting in 50,000 tons more reef fish (95% HPD: 7000–310,000).
What terrestrial invasive animal suppresses Chagos seabirds?
black rats Rattus rattus and coconut palm forest were introduced in the late 18th and early 19th centuries
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.
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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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