The third national Tree Officers Conference has heard a range of strategies employed by local authority tree managers to maintain tree stocks cost-effectively.
"Austerity isn’t over in local government," former Bristol City Council senior arboricultural officer Russell Horsey told the conference organised by the Municipal Tree Officers Association, the London Tree Officers Association and the Institute of Chartered Foresters.
"Tree officers need to tap into the departments of health and transport."
While admitting he hadn't got far with health, he listed some successes achieved in Bristol on the back of transport infrastructure projects, such as a £12m cycle lanes programme that brought new avenues of trees, or a bus route upgrading programme that yielded a further £550,000 for new trees, or nearly 20 times his annual tree-planting budget.
But this requires political support, early involvement and adaptability, including on tree pit design, he noted. Perhaps surprisingly, planting large trees in central reservations appeared to boost both public transport and cycling use, he said. "Highways engineers get excited about bums on seats."
He suggested to a delegation of arboriculture students present: "Sit in on a few planning and engineering lectures. It will help you in your careers."
North Somerset Council "has been under severe financial pressure for 12 years", said its principal tree officer Linda Saretok. "The priority now is to keep risk to an acceptable level. The question is how to manage 300,000 trees on £150,000 a year? How many can we realistically inspect and get work done on?"
On the council’s Tree Risk Management Plan, published in September, she said: "The detail is what makes it robust and defensible." This employs Quantified Tree Risk Assessment, which divides territory into "land-use ranges" such as highways or school grounds, and "relies on a common understanding of risk".
System built from scratch
Winchester City Council tree technician Claire Jakeman explained the process by which the Hampshire authority built its own tree management system "from scratch", and intended to be "proportionate to the resources available". Her colleague, tree officer Stefan Kowalczyk, explained this meant "moving from individual trees to zones each with a priority, and negative reporting — that is, you only report the bad stuff".
By employing the National Tree Map rather than the authority’s own "out-of-date and wrong" legacy system, and the skills of a "GIS geek" on the staff, it has been able to combine datasets to yield usable data, Jakeman explained. An external company then provided data on which to base assessments of risk from trees falling, leading to parcels of land being assigned priorities, Kowalczyk added.
An extra cost likely to be borne particularly by rural authorities, and an area where tree inventory management will be crucial, is the spread and progression of ash dieback (ADB). Norfolk County Council arboricultural and woodland officer Tom Russell Grant said: "ADB is progressing but not rampantly, and we can now budget a bit more accurately, though we are still at the thin end of the wedge."
The UK’s first confirmed case of the pathogen was in Norfolk in 2012. Having consulted with Fera on a surveying strategy, the council identified areas of highest risk. The trees highlighted for inspection are photographed, marked and assigned a value for canopy loss — 0, 25, 50, 75 and 100%, with those showing 75%-plus loss marked for action.
Grant noted: "We have to survey in summer and there is the question of secondary infections." He added that lesions and collar rots were not apparent in roadside trees as they were in woodland trees.
Elm problems identified
An assessment revealed that while ash trees made up the bulk of those requiring attention, "30% were elms, as we are still suffering from the effects of Dutch elm disease". He added: "Ash was supposed to fill the gap they left, and that has been pushed back 30 years. But we want to start recovering from this one as soon as possible. There needs to be some push to allow the next generation of trees to come through. The thing not to do is to cut down existing trees. They are the gene pool for the future."
Tree Council rural programmes director John Stokes said: "We will have guidance on ADB for local authorities by the end of January."
Giving a perspective on tree management in a different legislative context, Isle of Man arboricultural officer Andrew Igoea explained that every tree on the island above 8cm DBH (diameter at breast height) has automatic protection. With finite resources, this has meant adopting a system to prioritise protection measures in practice. It was suggested that such a law would discourage residents from planting trees on the island, a UNESCO Biosphere Reserve, to which Igoea said: "You would think. But they are nature lovers."
Meanwhile, Andrew McCutcheon, Guernsey’s principal environment services officer, warned that the Asian hornet, thought to have arrived in France in a consignment of pottery, "likes making big nests in trees, of up to 13,000 individuals". Having arrived on the Channel island in 2016, "it now takes out honeybees and is a public health risk," he said. "You will be hearing a lot more of it in future."