Influence of urbanization on vertebrate populations: an ecophysiological approach – URBASTRESS

It is expected that 70% of the world population will be urban by 2050. Therefore, guaranteeing the quality of life of urban populations is a crucial challenge for the upcoming decades. Since their settlement, cities have drastically changed and they are one of the environments where global changes are the fastest and most pronounced. Indeed, urban environments are perceived as an ecological desert, and this lack of wildlife is of particular concern for humans because contact with “nature” is crucial for the health and well-being of humans. Despite these constraints, some animals are able to inhabit in cities and studying these sentinel species can help us to better understand the impacts of urbanization on wild vertebrates, and thus, help us to improve the quality of life of human populations.

In this context, URBASTRESS proposes to focus on a human-commensal species, the house sparrow, to investigate the costs and benefits of urbanization. This species is especially relevant because it will allow us to evaluate the impact of ongoing and emerging urban constraints on one of the only wild vertebrate that is supposed to be well adapted to an urban lifestyle. Moreover, this project is timely because several European populations of sparrows have been declining in the past decades. To reach our aim, we will use an original approach that integrates methods and concepts of demography, physiology, ecology, and environmental health. To investigate the proximate causes of urban population trends of the house sparrow, this innovative project will span several scales of investigation from modifications of physiological performances at an individual level up to demographic processes. We will specifically study allostasis-related physiological mechanisms to assess the constraints of living in an urban environment, but also to test whether the physiology of this wild vertebrate species is flexible enough to allow them to adjust to these constraints. This project will specifically focus on the physiological mechanisms (stress response, immune and metabolic responses) that are likely to constrain and/or determine the ability of individuals to adjust to 3 environmental variables of interest (noise, pathogens, food shortage). Such approach is necessary to better assess (1) the relative impact of urban-related environmental factors on performances (costs and benefits); (2) the ability of individuals to adjust their phenotype to maximize the benefits of living in an urban environment while limiting its costs; (3) the potential of urbanization to mediate an ecological trap for urban dwellers.

To reach these objectives, we will first establish a large scale demographic survey to evaluate the environmental characteristics of the urban environment and to test their impact on the demography of sparrows. Second, we will evaluate the physiological constraints of the urban habitat and we will examine how urban individuals may physiologically cope with urban challenges (stress, pathogens, energetic constraints). Finally, we will assess the impact of these environmental and physiological constraints on individual fitness. For all these steps, we will use an experimental approach to test our working hypotheses. The success of this project will be guaranteed not only by the expertise of this young and productive team, but also by promising preliminary results.

This project will be of interest to a wide public because it targets a key societal question – the biological sustainability of an urban lifestyle – with complementary, relevant perspectives (ecology, physiology, demography) and actors (scientists, students, local government, volunteers, managers, citizens). To conclude, URBASTRESS will improve our knowledge of the urban constraints and will enable us to understand the way our closest urban vertebrate neighbors may cope with them. Therefore, URBASTRESS will allow us to advise policy-makers on how to improve the management of urban biodiversity.