Contribution of private gardens to habitat availability, connectivity and conservation of the common pipistrelle in Paris

Urban sprawl is one of the greatest global changes with major negative impacts on biodiversity. Recent policies have acknowledged the value of urban green areas in counterbalancing such impacts. However, these policies are largely focused on public green areas, ignoring the role and potential of private green areas for urban ecological value. This paper aims at evaluating the importance of private gardens for habitat availability and connectivity in Paris, France, using the common pipistrelle (Pipistrellus pipistrellus) as model species. We hypothesize that public green areas contribute more to habitat availability than private gardens because of their large area, and that private gardens contribute more to connectivity than public green areas because of their scattered locations in the city. Using data on common pipistrelle activity and information on vegetation and building height, we quantify the respective contribution of public green areas and private gardens in the bat habitat availability and connectivity. Our results show that despite the low proportion of private green areas in Paris (36% of the total green areas), they still contributed up to 47.9% of bat habitat availability and decrease the resistance of the city matrix by 57%. The distribution in the city matrix and vegetation composition of those areas appeared especially beneficial for bat habitat availability and connectivity. The study demonstrates the importance of private gardens in the ecological value of cities in complementing public green areas. Our results confirm the need to develop more inclusive urban conservation strategies that include both public and private stakeholders.