Threats to the barbastelle bat Barastella barbastellus are poorly understood, but its low population density and slow population growth make it particularly vulnerable to factors such as: (1) Further loss and fragmentation of ancient deciduous woodland habitat;
(2) Loss, destruction and disturbance of roosts or potential roosts in buildings, trees and underground sites;
(3) reduction in numbers of insect prey due to habitat simplification acting through factors such as fertiliser use and intensive grazing.
The barbastelle bat is mainly a woodland species. It uses old buildings and trees as summer roosts and underground sites and other suitable places such as hollow trees for hibernation. Riparian woodland may form an important habitat in some areas. It feeds mainly on lepidoptera taken in flight, but may also glean insects and spiders from vegetation.
Barbastella barbastellus is widely distributed in England and Wales with centres of population in south-west and mid-west England, and Norfolk. It is believed to be rare in the UK, with only 340 records since 1802. Only one UK maternity roost and less than 30 hibernation sites are currently known. The most recent UK population estimate is approximately 5000 individuals but the overall population trend is not known. The barbastelle bat is widespread in continental Europe, but appears to be rare almost everywhere.
Barbastella barastellus is considered as "Vulnerable" by the IUCN Red List. The species is listed on "Appendix II" of the Bonn Convention (and its Agreement on the Conservation of Bats in Europe, 1994), "Appendix II" of the Bern Convention (and its appropriate Recommendations) and Annexes II and IV of the EC Habitats and Species Directive.