Hedgerows should be left untrimmed for up to ten years in order to help the bat population, a new study has found.
The research, by the University of Bristol and the Bat Conservation Society, found that three of Britain’s rarest bat species – the Greater Horseshoe, Lesser Horseshoe and Plecotus – were found more abundantly in untrimmed hedges, as were their insect prey.
Currently, the law states that hedgerows should be trimmed only one year in three, unless permission is sought from the local council.
In the study, scientists monitored 64 hedges in various states of trim, and surveyed the wildlife they found in and around them over the summer of 2016.
They found that insect and bat species richness significantly increased with time since last trimming.
Taller hedgerows had more space for bat and insect life, and leaving them untrimmed creates a complex branch structure, perfect for wildlife to hide in.
Researcher Jérémy Froidevaux said: “While the less severe trimming regime prescribed by previous and current AESs in England encourages farmers to trim hedgerows only one year in three, our study largely supports the longer term benefits of non‐trimming on bats and their insect prey.
“Keeping some hedgerows untrimmed for up to 10 years would enhance bat species richness and insect family diversity. Overall, this study shines a light on the success of targeted agri-environment schemes for promoting some of the most threatened bat species in Western Europe”.