Opportunities for improving the foraging potential of urban waterways for bats

The rapid rate of urbanisation over the past century has occurred over a relatively small proportion of the earth's surface, yet it has had considerable ecological impact at a global scale. Urban waterways have historically been regarded as a disposable resource for human benefit which has had severe biological consequences. River rehabilitation schemes are attempting to address this; however restoration is frequently undertaken with minimal scientific input and fails to improve biodiversity. Many bat species are strongly associated with aquatic or adjacent riparian habitats but respond negatively to the built environment; however, we know little about the utilisation of urban waterways by bats. We therefore conducted a wide scale, multi-species study that examined how local habitat characteristics and the composition and heterogeneity of the surrounding landscape influence bat presence and activity along urban waterways. We recorded a total of 19,689 bat passes of seven species/genera from 30 urban waterways throughout the U.K. We show that the built environment can negatively affect a variety of species from the riparian zone up to 3 km from a waterway. Additionally, Myotis sp. activity was greater in waterways bounded by steep banksides and clear of invasive plant species. We also found differences in the response of two cryptic pipistrelle species to the built environment at multiple spatial scales indicating the difficulties of assessing how adaptable even morphologically similar species are to urbanisation. Beneficial urban waterway rehabilitation schemes for bats require management at multiple spatial scales. At a local scale, retaining a vegetated riparian zone, with a reduction in invasive aquatic plant species, is likely to benefit a variety of taxa. At a landscape scale, our results show that the influence of the built environment can stretch a considerable distance highlighting the necessity for conservation funding to be spent on the implementation of landscape scale environmental improvement schemes which encompass the entire urban matrix.