Birds influence vegetation coverage and structure on sandy biogeomorphic islands in the Dutch Wadden Sea

Valérie C. Reijers*, Floris van Rees, Tjisse van der Heide, Albert P. Oost, Gerben Ruessink, Kees Koffijberg, Kees C.J. Camphuysen, Emma Penning, Nadia Hijner, Laura L. Govers

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Small uninhabited islands form important roosting and breeding habitats for many coastal birds. Previous studies have demonstrated that guano can promote ecosystem productivity and functionality on island ecosystems. Here, we assess the role of external nutrient input by coastal birds on the vegetation structure and coverage on sandy biogeomorphic islands, where island-forming processes depend on vegetation-sedimentation feedbacks. As a first step, we investigated whether breeding birds affect vegetation productivity on sandy back-barrier islands in the Wadden Sea. Using a combination of bird observations and plant stable isotope (δ15N) analyses, we demonstrate that (i) breeding birds transport large quantities of nutrients via their faecal outputs to these islands annually and that (ii) this external nitrogen source influences vegetation development on these sandy, nutrient-limited, islands. Based on these results we discuss how this avian nutrient pump could impact island development and habitat suitability for coastal birds and discuss future directions for research. In general, we conclude that avian subsidies have the potential to affect both the ecological and biogeomorphic functioning of coastal soft-sediment systems. However, the strength and scale of especially these biogeomorphic interactions are not fully understood. For the conservation of both threatened coastal birds and sandy back-barrier islands and the design of appropriate management strategies, we argue that three-way interactions between birds, vegetation and sandy island morphodynamics need to be further elucidated.

Original languageEnglish
Article number175254
Pages (from-to)1-13
Number of pages13
JournalScience of the Total Environment
Volume950
DOIs
Publication statusPublished - 10 Nov 2024

Bibliographical note

Publisher Copyright:
© 2024 The Authors

Funding

We like to thank Wim Jan Boon, the crew of the Harder and the Ambulant for transporting us to the islands. We thank Natuurmonu-menten and Staatsbosbeheer for granting us access to these protected nature reserves and facilitating bird surveys. We thank Selin Ersoy for her help collecting data in the field and Germa Verheggen, Roy Peters, Paul van de Ven and Evaline van Weerlee for their help with lab ana-lyses. We thank Sovon for sharing data on bird nests and Date Lutterop and Giny Kasemir (Natuurmonumenten) specifically for data and poop sample collection. V.C.R. and L.L.G. were funded by OBN project 'habitat-overstijgende interacties'. L.L.G. and E.P. were funded by a grant from Waddenfonds and Rijkswaterstaat, for the project 'dynamic Griend'. F.v.R. was funded by UU-NIOZ project 'Avian nutrient pump'. T.v.d.H. was funded by NWO/TTW-Vidi grant 16588, L.L.G. by NWO-VENI grant 016.Veni.181.087 and V.C.R. by NWO-VENI grant VI. Veni.212.059.

FundersFunder number
Ambulant - OBN project 'habitat-overstijgende interacties'
Waddenfonds and Rijkswaterstaat - NWO/TTW-Vidi grant16588
NWO-VENI grant016, Veni.181.087
NWO-Veni

    Keywords

    • Biogeomorphic feedbacks
    • Coastal birds
    • Ecosystem connectivity
    • Guanofication
    • Island morphodynamics
    • Stable isotopes

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