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Data from: Contrasting conclusions in the study of wetland bird abundances show the importance of multi-level insights into protection and restoration actions

Lehikoinen, Petteri1; Xu, Yanjie21; Mikkola-Roos, Markku2; Lehikoinen, Aleksi1; Jaatinen, Kim2

Published Sep 01, 2026 on Dryad. https://doi.org/10.5061/dryad.bcc2fqzvq

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Abstract

Wetland biodiversity has declined around the world due to habitat loss and degradation. To alter this trend several management actions still are taken including protection and restoration. The management responses may vary across analytical scales including species, functional groups and total waterbird abundance, but it is rarely investigated how similar conclusions these approaches yield. 2. We evaluated how wetland protection and small-scale restoration actions influenced breeding waterbird abundances and species richness by using a 34-year dataset (1986–2019) from 994 naturally eutrophic wetlands across Finland. Protected wetlands supported higher waterbird abundances and species richness than unprotected sites, indicating successful conservation prioritisation. Contrary to expectations, population trends at protected sites were generally more negative than at unprotected wetlands; a finding potentially related to the higher initial waterbird numbers at protected sites allowing a decline not possible at unprotected sites that harbour less waterbirds. Inference depended strongly on the response metric: species-specific models suggested stable or increasing trends, whereas total abundance models revealed overall declines. Within protected wetlands restored sites exhibited higher abundances and species richness than unrestored sites. However, wetlands restored with multiple restoration actions showed more negative total abundance trends than those restored with one action. Responses varied markedly among guilds and species, with increases in some groups (e.g. large herbivores) and persistent declines in several diving species. Species richness trends did not differ among protection or restoration categories. Wetlands selected for protection and restoration harbour high biodiversity value but may still experience declining water bird populations, likely reflecting broad-scale environmental pressures not mitigated by the small-scale protection and restoration. Contrasting results between species-specific and total abundance models highlight the importance of using multiple response metrics when evaluating management effectiveness. Conservation assessments should thus integrate species-, functional-group- and community-level indicators and address drivers operating beyond site boundaries, including catchment-level processes. These findings provide evidence-based guidance for large-scale wetland restoration and management initiatives, including national programmes and the EU Nature Restoration Regulation.