Rat eradication restores nutrient subsidies from seabirds across terrestrial and marine ecosystems

Type Article
Date 2021-06
Language English
Author(s) Benkwitt Cassandra E.1, Gunn Rachel L.1, Le Corre Mathieu2, Carr Peter3, 4, Graham Nicholas A.J.1
Affiliation(s) 1 : Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
2 : UMR ENTROPIE, Université de La Réunion, IRD, CNRS, IFREMER, Université de Nouvelle-Calédonie, Avenue René Cassin, 97490 Sainte Clotilde, La Réunion
3 : Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK
4 : Environment and Sustainability Institute, University of Exeter, Penryn Campus, Cornwall TR10 9EZ, UK
Source Current Biology (0960-9822) (Elsevier BV), 2021-06 , Vol. 31 , N. 12 , P. 2704-2711.e4
DOI 10.1016/j.cub.2021.03.104
WOS© Times Cited 20
Keyword(s) coral reef, cross-ecosystem nutrients, eradication, invasive species, island nutrient subsidy, rat ecosystem recovery, seabird tropics

Biological invasions pose a threat to nearly every ecosystem worldwide.1,2 Although eradication programs can successfully eliminate invasive species and enhance native biodiversity, especially on islands,3 the effects of eradication on cross-ecosystem processes are unknown. On islands where rats were never introduced, seabirds transfer nutrients from pelagic to terrestrial and nearshore marine habitats, which in turn enhance the productivity, biomass, and functioning of recipient ecosystems.4, 5, 6 Here, we test whether rat eradication restores seabird populations, their nutrient subsidies, and some of their associated benefits for ecosystem function to tropical islands and adjacent coral reefs. By comparing islands with different rat invasion histories, we found a clear hierarchy whereby seabird biomass, seabird-driven nitrogen inputs, and the incorporation of seabird-derived nutrients into terrestrial and marine food chains were highest on islands where rats were never introduced, intermediate on islands where rats were eradicated 4–16 years earlier, and lowest on islands with invasive rats still present. Seabird-derived nutrients diminished from land to sea and with increasing distance to rat-eradicated islands, but extended at least 300 m from shore. Although rat eradication enhanced seabird-derived nutrients in soil, leaves, marine algae, and herbivorous reef fish, reef fish growth was similar around rat-eradicated and rat-infested islands. Given that the loss of nutrient subsidies is of global concern,7 that removal of invasive species restores previously lost nutrient pathways over relatively short timescales is promising. However, the full return of cross-ecosystem nutrient subsidies and all of their associated demographic benefits may take multiple decades.

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