Abstract
While freshwater habitats cover less than 1% of the Earth’s surface, they host about a quarter of the vertebrate species, including about half of all the fish species. This global diversity of freshwater fishes is, however, increasingly and disproportionally threatened by multiple human pressures. Our understanding of the cumulative impacts of these pressures is limited due to the multitude of impact pathways and interactions as well as data restrictions. Filling this knowledge gap is both urgent and challenging, not the least because interactions among pressures may lead to so-called ‘ecological surprises’. Drawing on a novel combination of species traits and species distribution modelling, this project aims to quantify and unravel the cumulative impacts of four major human pressures (climate change, land use, chemical pollution and habitat fragmentation) on global freshwater fish diversity. How species respond to and interact with their environment, ultimately giving rise to their distribution, is governed by their traits. Therefore, we will first retrieve key traits that underlie species distributions (physiological tolerance, dispersal capacity, habitat area requirements) from known species properties. We will then use this trait information to enrich correlative species distribution models that estimate the probability of occurrence of each fish species in relation to relevant water quantify and quality variables affected by the pressures. Finally, we aggregate the species-level models into a global model of freshwater fish diversity. We will use the newly developed freshwater fish diversity model to quantify the relative and combined impacts of the different pressures by evaluating changes in fish species distributions in response to each pressure separately and to their combinations. This factorial approach generates novel insights in potential synergistic and antagonistic interactions among pressures and also helps to identify effective options for conserving or restoring freshwater fish diversity.
Netherlands