Habitat availability decline for waterbirds in a sensitive wetland: Climate change impact on the Ebro Delta

• SDM predicts up to 70 % habitat loss for waterbirds in Ebro Delta by 2100 due to sea-level rise. • Temperature, precipitation, and terrain elevation are key factors in waterbird habitat suitability. • Sea-level rise dramatically reduces viable habitats, highlighting urgent conservation needs. • Conservation efforts must focus on managing alternative habitats like flooded crops and salt pans. The highly biodiverse, productive and vulnerable areas, such as coastal wetlands, are increasingly threatened by human-induced disturbances, resulting in habitat loss. This habitat loss is a critical driver of biodiversity decline and significantly impacts species distribution and behavior, increasing the risk of extinctions. To address these concerns, we developed a Species Distribution Model (SDM) using a decade-long dataset of waterbird functional group occurrences in the Ebro Delta, with a particular focus on the Ardeidae family, which represents the most prominent species in the wetland. This model aims to predict potential habitat loss under various climate change scenarios, specifically those outlined in the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCP) 4.5 and 8.5, across three distinct time periods. Our SDM revealed that habitat suitability for waterbirds was notably influenced by temperature variations, increased cumulative precipitation, and lower terrain elevation. Predictions indicate an increase in available habitat for these waterbird species over the study periods considering the specified climate scenarios. However, the incorporation of sea-level rise and flooded areas into the models unveiled a dramatic decline in available areas for waterbirds in the long-term, reaching up to 50 % (RCP 4.5) and 70 % (RCP 8.5) reduction. Our study highlights the urgent need for conservation efforts to mitigate the substantial reduction in available habitat for waterbirds. This need is especially crucial due to the Ebro Delta's importance as a vital coastal wetland for many thousands of waterbirds throughout their entire life cycle. Immediate and targeted conservation actions are imperative to safeguard the essential habitats for these species.