Functional Diversity Responses to Temperature Vary Spatially and With Protection Status in Wintering Waterbird Assemblages.

Wetlands support disproportionately high biodiversity, including waterbirds, which underpin key ecological functions and regulatory services. This has led to efforts to protect these crucial sites, but whether these protections can maintain waterbird assemblages in the face of new threats such as climate change is poorly understood. Here, we calculated functional redundancy and three metrics of functional diversity from over 45,000 waterbird censuses, spanning four decades of rising winter temperatures for 2792 protected and unprotected sites in Europe. We modelled the effect of average winter temperature and the trend over time for each of these metrics. Our results suggest functional diversity generally increased in warmer winters and over time, but redundancy declined, and the effect of temperature varied spatially and between levels of protection. This suggests abundance and distribution shifts due to climate change are altering functional diversity and resilience of waterbird assemblages both inside and outside protected areas across Europe.