Bats declined as Britain felled trees for colonial shipbuilding - Bat Conservation Trust

Bat numbers declined as Britain’s trees were felled for shipbuilding in the early colonial period, new research shows.

The study, by the University of Exeter and the Bat Conservation Trust (BCT), found Britain’s Western barbastelle bat populations have dropped by 99% over several hundred years.

Animals’ DNA can be analysed to discover a “signature” of the past, including periods when populations declined, leading to more inbreeding and less genetic diversity.

Scientists used this method to discover the historic decline of Western barbastelles in Britain – and also analysed modern landscapes to see what helps and harms bats.

They found more genetic diversity among bats in areas rich in broadleaf woodland and diverse habitats.

Artificial light reduced connectivity between populations, probably because bats avoid areas with bright lighting, while rivers and woodlands increased connectivity.

“These bats usually roost in mature oak and beech trees, and move around every few nights – so they benefit from areas with substantial woodland cover,” said Dr Orly Razgour, from the University of Exeter. “Our findings reveal that both the northern and southern British barbastelle populations have declined over several centuries, beginning about 500 years ago. This coincides with a period of widespread tree-felling to supply wood for colonial shipbuilding. It is likely that the decline we found was triggered by this loss of woodland – which has continued since that period.”

Barbastelles give birth in early summer, with mothers raising a single pup each year.

The species’ habit of moving frequently makes population surveys difficult, so the study provides a valuable update on their status (they are classified as “near threatened” globally, and “vulnerable” in the UK).