Tree-risk insight offered at Kew

System based on Tree Risk Assessment Qualification.

AGM: Consulting Arborist Society held meeting at Kew, home to many historically and botanically important trees - image: HW
AGM: Consulting Arborist Society held meeting at Kew, home to many historically and botanically important trees - image: HW

The Consulting Arborist Society (CAS) AGM held at Royal Botanic Gardens, Kew on 24 June gave consultants insights into how Kew manages the risk arising from its collection of 14,000 trees, many important historically, botanically or both.

"You can't just fell trees because they're looking a bit ropey," said arboricultural manager Kevin Martin. He explained how following the death of a Kew visitor from a falling branch in 2012, a more systematic form of tree risk management has been implemented in the gardens based on the Tree Risk Assessment Qualification (TRAQ) approach developed in the USA by the International Society of Arboriculture.

Martin became a qualified TRAQ user in 2014. Then three months ago, he and his team of four switched to a purpose-built app for Android tablet and desktop PC that incorporates the TRAQ format. "It's been a long, expensive process to develop the app from scratch and now there is talk of selling it," he said.

This indicates tree issues via "pins" on zoomable maps of the garden, with four-part colour coding indicating priority level. This then forms the basis of work scheduling and in turn enables subsequent auditing and performance monitoring. "That helps with funding and resourcing," Martin explained. "If I get behind, I can say to the trustees 'this is work that needs doing'."

He added: "At the court case, information came from everywhere. This keeps the whole history of the tree all together and has allowed us to build a defensible case around a form of risk-assessing trees, showing when and how each inspection was carried out. The court doesn't care what system you use as long as you have a process to pick up and deal with defects. It also probably saves me one day a week (in record-keeping)."

Giving examples of specific solutions employed in the gardens to maintain or revive struggling trees, he pointed out that some were suffering from questionable decisions in recent decades, rather than merely the ravages of time.

He said of a famous prostrate "suffering" Japanese pagoda tree (Styphnolobium japonicum syn. Sophora japonica) in the gardens: "We took out four tonnes of gravel over a weed barrier. Underneath the soil was completely compacted and barren. We have put in a lot of organic material from the yard topped off with a woody mulch for insulation. Now it's quite green again."

On the various forms of bracing that are employed for the gardens' trees, Martin said: "They have gone out of fashion and we have started taking them out, though you can't where the tree has adapted to them."

Air-spading and incorporating biochar have also helped individual trees suffering from soil compaction, he added, while a policy of staged "natural retrenchment" is enabling retention of older, stag-headed specimens. But he admitted: "These measures wouldn't necessarily be cost-effective for a local authority."

He also pointed out: "Sometimes it's easier to manage the target rather than the defect - such as leaving a swathe of long grass around the tree." He also admitted that the gardens' benches, which are not fixed down, are "a nightmare", saying: "If it's a tree I worry about, someone will drag a bench to it. But they've paid to come in and it's another thing to manage."

A "back-of-a-fag-packet calculation" showed that a Kew visitor would have a one-in-150-million chance of being struck by a branch, said Martin. He concluded: "Sometimes we have to take a step back and be less risk-averse, otherwise we wouldn't have any interesting or heritage trees."

CAS is the sole licensed deliverer of TRAQ training in the UK and executive director Mark Chester is working towards becoming a certified trainer. He told the meeting: "I wanted to road-test all the courses CAS offers to ensure they are fit for purpose. TRAQ is by arborists, for arborists, and it's a work in progress rather than a finished product."

He explained: "Arborists have the threat of litigation hanging over them. But only one of the 12 court cases in the last 10 years has found for the claimant. 'If in doubt, take it out' is neither sustainable nor justifiable. I've seen lots of local authority trees felled that didn't need to be. The risk from trees is quite low and the HSE (Health & Safety Executive) recognises this. But you need a tool to justify keeping them."

At the AGM, Surrey-based consultant Tom Thompson was elected CAS chairman. Previous chairman Bob Widd became treasurer, with Chester remaining executive director. Membership has risen from fewer than 50 seven years ago to around 170 now, said Chester.

Fund4Trees: Seeking new forms of support from figures in industry

Independent arboricultural consultant Russell Ball told the Consulting Arborist Society meeting that his Fund4Trees initiative is looking for new forms of support from industry figures.

So far the fund's sponsored cycle rides, school visits and tree plantings have already reached 3,000 schoolchildren and raised around £26,000 for arboriculture-related research. "But we can do more," said Ball.

"We still want to do the rides but we want the industry to step up, either by donating proceeds from one job a year, or one hour a month, by direct debit. That way we don't have funding spikes over the year and the cyclists don't have to keep going back to the same sponsors."

Last year the fund supported tree fungi research at the University of Cardiff, urban tree and climate change research at Myerscough College and the publication of a best-practice guide by Trees & Design Action Group Midlands.

Ball said: "We are a charity with four trustees, none of whom claim anything - it all goes to the work."

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