‘Sitting Ducks’ in a Megacity: What Do Waterbirds Tell Us about the Effectiveness of Lake Restoration?

Mihir Ravindra Kulkarni  | 5 June 2024 

Rapid urbanization is globally transforming natural landscapes, one of the consequences of which is the rapid degradation of habitats and associated biodiversity loss. Habitat degradation and biodiversity loss are linked to loss of ecosystem functioning and the consequent reduction of vital ecosystem services. These challenges are more pronounced for freshwater habitats, particularly in developing tropical economies. Restoring degraded habitats is thus an important area for research, action, and policy. In India, several urban lake restoration projects are undertaken, yet few studies attempt to evaluate their effectiveness through an ecological perspective. I examined the impacts of lake restoration projects on waterbird assemblages in Bengaluru, a megacity in peninsular India. Using long-term citizen-science data on waterbird occurrences in 66 lakes (49 restored, 17 unrestored) across the city, I estimated the α and β-diversity of waterbird assemblages. I used taxonomic, functional, and phylogenetic metrics to understand the community assembly in these habitats and to assess the impact of restoration measures. α-diversity in restored and unrestored lakes did not differ significantly. β-diversity patterns were shaped by species replacements in restored lakes, and nestedness in unrestored lakes. Pairwise comparisons in assemblages from restored and unrestored lakes revealed the strong contribution of nestedness. These indicate the role of species interactions and environmental filtering in shaping the communities, which is also supported by the functional overdispersion (co-occurrence of functionally different species) and phylogenetic clustering (co-occurrence of phylogenetically related species). These indicate a partial recovery of the waterbird biodiversity in the restored lakes. However, the dominance of species interactions, rather than environmental variation in shaping communities in restored lakes potentially reflects the response to restoration practices which overlook/reduce natural habitat heterogeneity. I use these preliminary observations to a) discuss lake-restoration practices in India, b) highlight the need for detailed studies, and c) underscore the importance of ecology-based restoration.