Are Treatment Wetlands suitable surrogate habitats for birds? A study on avian diversity in Northern Italy

Wetlands provide critical ecological and conservation benefits but are increasingly threatened by urbanization and agricultural expansion. Treatment Wetlands (TWs) offer an innovative conservation tool, combining wastewater treatment with potential habitat restoration, yet their effectiveness as surrogate habitats for birds remains underexplored.

This study assessed the ecological value of TWs by comparing bird diversity between two habitat types: Free Water Surface wetlands (the most wetland-like among TWs) and semi-natural wetlands (dry landscapes were used as controls). Bird diversity was evaluated using Hill numbers, repeating the analyses on the entire bird assemblage and then only on waterbirds, identifying relationships between diversity and environmental variables.

Overall, bird diversity did not differ significantly between TWs and semi-natural wetlands and was even higher in TWs under certain circumstances. Moreover, analyses restricted to waterbirds confirmed that diversity was comparable between TWs and semi-natural wetlands, particularly in terms of species richness. Key environmental variables characterizing TWs positively associated with waterbirds diversity included the extent of free water, reedbed coverage, and surrounding urbanization.

Therefore, TWs can function as effective surrogate habitats for birds, providing ecological value comparable to semi-natural wetlands and supporting a similar diversity. By mimicking and restoring critical wetland habitats, TWs offer a dual benefit of wastewater treatment and diversity conservation. These findings underline the potential of TWs to play a pivotal role in sustainable landscape management. Further research should explore their performance relative to larger or fully natural wetlands to optimize their integration into conservation strategies.

In each folder, you can find the various dataframes related to a sampling season. These include both those containing bird abundance data and environmental data. Additionally, the R script is also provided.