Veteranisation – Bat Conservation and Old Wood Features

24 Mar

Back in March 2020, the Bat Conservation Trust (BCT) had organised a Woodland Bat Symposium at the WWF’s Living Planet Centre in Woking, Surrey. Only days before the battiest people from across the country were due to meet and share the latest news on bats in woodland habitats, the national conference was postponed - the first Covid-19 lockdown was around the corner. I was due to attend the conference to present a talk about how the Woodland Trust has been managing woodland habitats for barbastelle bats and the scientific research that had been achieved in some of the woods around Dartmoor. But, along with many large gatherings at the time, the initial conference was postponed and, after a few changes of date, it was arranged as an online conference in November.

Natural old-growth features in broadleaved trees
Natural old-growth features in broadleaved trees

So, there we were. Over 160 people all sitting at home, sharing and absorbing two days of talks about bats and woodlands. It was packed with fascinating speakers and very well organised and chaired by BCT. Batty people, from scientists and researchers to woodland managers and conservationists, all chipped in with their latest information, research results and advice. Staring into a screen for two content-packed days can be quite intense and, towards the end of day two, it was my turn, but it was really one of the other speakers that caught my attention. Vikki Bengtsson, a woodland conservationist and researcher, spoke about how, over 20 years, she has become a leader in the field of ‘veteranisation’ or, as she describes it “using tools instead of time” to create features in trees that may initially look like damage but are intended to accelerate the ageing processes, mimicking the effects of time on ancient trees. She talked about the techniques used and how they should not usually kill the trees, but instead encourage the decay process to develop at a younger age, thus potentially shortening the development time for habitats usually only found in old trees.

Natural deadwood - roosting features for bats
Natural decay holes - roosting features for bats

Among the beneficiaries of veteranisation processes are the bats that inhabit woodlands. These old features created in younger trees would increase the potential for shelter and roosting features and, with additional areas of decaying wood, support the whole food web that bats rely on. This important relationship was demonstrated by research in some of the woods around Dartmoor (see the ‘Bats of Dartmoor’s Wooded Valleys’ online talk by Dr Andrew Carr and Tom Williams)

Ancient and veteran trees will already be developing these features but there are often too few veteran trees in our woods and Vikki said there is a big age gap between the young trees and the veterans. “This is one of the biggest challenges facing old trees – there aren’t enough of them.” In her presentation, she spoke about mimicking the action of horses’ hooves and bears claws, the kind of wear and tear inflicted by large fauna that are limited these days, processes that are distant in the memory of our woods.

Volunteers work to accelerate old growth features
Old growth feature

With more study, we are getting a better understanding of the importance of trees with veteran features. They provide niches where fungi can take hold or places for invertebrates to survive. The more obvious features may provide a hole for a bird, a cavity for a mouse or a roost for bats and, listening to Vikki being interviewed in a recent podcast, she is passionate about what she does, and that enthusiasm is infectious. When talking about ‘younger’ trees under 100 years old she says, “we can use trees you would otherwise remove.” As we have seen, the conifers grow fast and shade the surrounding trees. To avoid the loss of old trees we can “use younger trees that are shading out the older trees in a creative way”. This chimes with what is happening with the restoration work at Fingle Woods. Volunteers have already done a bit of work on some of the smaller trees but, perhaps there is a role in Dartmoor’s woods for more veteranisation of conifers, creating habitat opportunities deep in the plantations where biodiversity can be low. I asked Vikki about this and she replied, “there is little experience of veteranisation of conifers that I know of,” but suggested, “clearly veteranisation may have a place. Often it is better to do a combination of techniques. Some which actually kill the trees and others that veteranise. This is the approach we have taken in monoculture beech plantations to create more dynamic, variation and decaying wood.”

Windblown conifer 'snags' provide features for birds, insects and fungi
Windblown conifer 'snags' provide features for birds, insects and fungi
Windblown conifer 'snags' provide features for birds, insects and fungi

I frequently chat to Tom Williams about his bird survey work in the woods. He had recently been reading about the habitat requirements of two different species of treecreepers. The one that inhabits the UK is the Eurasian treecreeper that is often seen to favour conifer trees so, perhaps a few more veteranised conifers may support this bird to find food under the flaking bark. In addition, with the in-depth knowledge that has built up about woodland bats and their habitats in the Bovey Valley Woods, it would be appropriate to do some new work here. Research has linked bat roosting to the number of available roost features – another reason to enhance those suitable old-growth features. As well as providing good habitat for decay fungus, invertebrates, birds and bats, Vikki also pointed out that we are pushing the boundaries of knowledge. Referring to the appearance of wood mice in some of the created holes, she said, “there is a whole world of cavity ecology that we don’t know anything about”. In these holes and cavities, there is clearly room for further study and greater understanding.

by Matt Parkins

(Please note: Woodland management work, as described above, is not carried out at this time of year)

Listen to the Ancient Tree Forum podcast: click here

Read more about veteranisation work by volunteers Fingle Woods Blog

This edition of the Woodland Trust’s Wood Wise magazine is also interesting (see p.12)