Wetland creation and restoration for biodiversity : outcomes of conservation initiatives to benefit birds, amphibians and occasionally fish

Wetlands are one of the world’s most important ecosystems, but they are largely destroyed, modified, polluted and degraded. This has resulted in declines in wetland biodiversity, including that of birds, amphibians and fish. To mitigate those declines, many wetlands have been created and restored worldwide. Still, we lack large-scale wetland evaluations of the effects of wetland creation and restoration on biodiversity. In this thesis, I compared local and landscape effects to infer community responses to wetland creation. I then analysed species associations to find synergies and differences across taxonomic groups. Finally, using before-after surveys, I quantified the realised effect of wetland restoration on wetland bird communities. In general, created wetlands attracted most species of the regional freshwater community: 80% of bird and amphibian species and 50% of fish. Local habitat characteristics did relate differently to the bird, amphibian and fish community. Wetland birds were positively related to wetland size and proportion of flooded areas but negatively with the proportion of forest in the surrounding habitat. Water vegetation cover was positively associated with amphibian occurrence but negatively with bird abundance. Fish occurred more often in betterconnected wetlands, while amphibians at isolated wetlands. Bird reproductive success and fish species richness was lower in wetlands surrounded by forested landscapes. It seems that several small wetlands are better for wetland bird reproductive success and similar for adult bird abundance and richness than a single large wetland. Although estimates are uncertain, the results suggest that bird-fish and amphibian-fish negative associations indicating conservation conflicts and bird-amphibian positive associations indicating a potential for bird-amphibian conservation synergies when creating wetlands. Finally, before-after surveys revealed that wetland restoration notably increased local populations of several bird species (gulls, terns, grebes, diving ducks, swans, dabbling ducks, geese, smaller waders). Nonetheless, the species-specific effects between wetlands were highly heterogeneous, and some restorations caused population declines (shrub passerines). The results of this thesis thus add important knowledge regarding how wetland creation and restoration can be improved to achieve cost-effective conservation actions to support bird, amphibian and perhaps even fish communities