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Vertebrate scavenger assemblages and their functioning differ between artificial and natural wetlands: Implications for ecosystem management

Abstract:

Natural wetlands perform essential ecological functions, but their area has dramatically decreased. Partly to counteract this loss, artificial wetlands have been created. While studies comparing animal communities between artificial and natural wetlands abound, research on their comparative ecological functions is scarce. In particular, vertebrate scavengers in aquatic ecosystems have been little studied despite their critical role in nutrient cycling. This study compared vertebrate scavenger assemblages and their consumption patterns in natural and artificial wetlands in Doñana, Spain, to evaluate the effects of wetland management (natural vs. artificial hydrology) across different seasons. We placed 120 carcasses (carp and chicken) in natural and artificial wetlands. We recorded 22 vertebrate scavenger species efficiently consuming 100 % of carrion in an average of less than two days, highlighting their role in nutrient recycling. Carrion of aquatic-origin was consumed faster and by a greater variety of species than that of terrestrial-origin, facilitating the transport of essential nutrients from water to land. Artificial wetlands exhibited higher efficiency in carrion removal (twice as fast as natural wetlands). However, they hosted less diverse assemblages, dominated by opportunistic and non-native species. This suggests that artificial wetlands are not replacing natural wetlands in terms of biodiversity, despite sustaining water levels and functions. Importantly, ‘kidnapping’ water for irrigation reduces the ability of natural wetlands to maintain ecological functions provided by scavengers. Urgent regulation of water abstraction from aquifers, especially for crop irrigation, is necessary to maintain minimum groundwater levels, preserving the functionality and ecological processes of this critical wetland complex.