Drivers of European bat population change: a review reveals evidence gaps

Abstract

1. Bat populations are thought to have suffered significant declines in the past century throughout Europe. Fortunately, there are some signs of recovery; for instance, of the 11 species monitored in the UK, population trends of five are increasing. The drivers of past losses and recent trends are unclear; identifying them will enable targeted conservation strategies to support further recovery. 2. We review the evidence linking proposed drivers to impacts on bat populations in Europe, using the results of a previous cross-taxa semi-quantitative assessment as a framework. Broadly, the drivers reviewed relate to land-use practices, climate change, pollution, development and infrastructure, and human disturbance. We highlight where evidence gaps or conflicts present barriers to successful conservation and review emerging opportunities to address these gaps. 3. We find that the relative importance or impacts of the potential drivers of bat population change are not well understood or quantified, with conflicting evidence in many cases. To close key gaps in the evidence for responses of bat populations to environmental change, future studies should focus on the impacts of climate change, urbanisation, offshore wind turbines, and water pollution, as well as on mitigation measures and the synergistic effects of putative drivers. 4. To increase available evidence of drivers of bat population change, we propose utilising advances in monitoring tools and statistical methods, together with robust quantitative assessment of conservation interventions to mitigate threats and enable the effective conservation of these protected species.

Structurally rich dry grasslands – Potential stepping stones for bats in open farmland

“…Consequences of agricultural intensification, such as habitat and connectivity losses, are among the major drivers of bat population declines (Browning et al, 2021). While mainly associated with forests and partly urban areas for roosting, bats utilize a variety of habitat types during their nightly foraging trips of several kilometers (Dietz and Kiefer, 2016).…”

Don’t forget subterranean ecosystems in climate change agendas

“…Of these, many provide important ecological services including seed dispersal and pollination of both timber and food crops, as well as the consumption of agricultural pests 14 . Rising temperatures may cause current summer roost caves to become too warm impeding maternity activities, as well as arouse bats from hibernation during times of low prey availability 15 . These changes could facilitate further population declines, which would spur a reduction in bat ecological services.…”

Foraging Time and Temperature Affected Birth Timing of Rhinolophus ferrumequinum and Predicted Year-To-Year Changes for 25 Years in a Population in West Wales, U.K.

“…The date that bats leave hibernation sites and return to the roost is crucial since hibernation and the reproductive cycle are linked (Racey, 1973;Racey and Swift, 1981;Racey and Entwistle, 2003). Climate may be the most important driver of bat population change (Browning et al, 2021) and the detrimental effect a rise in temperatures on European bat species, in colder regions, is predicted to cause some extinctions by the end of the century (Rebelo et al, 2010). Pipistrellus kuhlii has shifted its range northwards and it is likely that it will lose the southern portion of Europe (Sachanowicz et al, 2006;Smeraldo et al, 2021).…”