Arborists, gardeners, officials, landowners and the public are considerably better informed about the value of ancient trees than a decade ago, and much of the credit for this must go to the Ancient Tree Forum (ATF), which celebrated its 10th anniversary in October.
According to forum chairman Neville Fay: "We have moved on a phenomenal way in that time. The value and benefits they bring from a biodiversity point of view is now accepted - they are seen as worthy of retention for that reason."
Established by the then English Nature & Countryside Agency, the ATF brings together a diverse group of professionals and enthusiasts ranging from ecologists to landowners. "Trees of great size are not prolific in northern Europe - the UK has around 80 per cent of them," says Fay. "And I think we have advanced the sophistication of conservation management further here than elsewhere."
The consultancy Treeworks Environmental Practice, which Fay heads, has surveyed between 10,000 and 20,000 veteran trees, both in major sites like Hatfield Forest and Dinefwr Park, and also "dotted around", he says. "My own estimate is that there are around nine million veteran trees, out of a total UK tree population of 900 million."
The defining feature of an ancient tree is that it has survived beyond full maturity and shows clear signs of ageing. "For a true veteran, you are looking for four or more features - deadwood, hollowing, or even 'phoenix tree' qualities of regeneration," says Fay.
An indication of the rising profile of ancient trees in the wider horticultural world came last month when a touring seminar organised by the Heritage & Botanic Garden Bursary Scheme (HBGBS) attracted three times as many historic gardeners as arborists, says HBGBS organiser Fiona Dennis. "Gardeners may only have responsibility for one ancient tree, but there's still plenty they can do - for example looking after the soil," she says.
A key issue for both gardeners and arborists is whether or not to keep deadwood in trees, says Fay, who co- presented the seminars. "Ornamental gardens typically have very little deadwood, and in historical landscapes it may be regarded as unsightly.
"There is even a British Standard - BS3998 - that covers cleaning up trees. But deadwood is fundamental to nutrient recycling and to their value as habitat." Such habitat is one of the rarest around - a fact acknowledged in the current UK Biodiversity Action Plan, he adds.
Previously, site surveys would have classed such signs of ageing in a tree as "delapidations", he says. "Now they are seen as assets, with implied responsibility for their management."
The Health & Safety Executive has consulted with the arboriculture industry to produce guidance for its own regulators acknowledging this.
The public profile of ancient trees is also on the rise. "It's a charismatic subject and engages people," says Fay. "Some have given up their lives to it."
"Witness trees" such as the Anne Frank tree in Amsterdam, which was recently spared felling after a public outcry, show how important individual trees can be to people, he says. "Once trees have a name, communities recognise them, and that interest helps preserve them."
In terms of threats to their future though, ancient trees are not out of the woods yet. Fay lists nitrification, agricultural and development pressures and climate change among the threats to their survival.
Conscious of this, the Tree Council launched its Green Monuments campaign five years ago to try to secure for historic trees the same protection as for historic buildings. "They have no inherent protection, unless they're in a Site of Special Scientific Interest," says Fay. "That gives you a very significant duty to retain trees, often with minimal intervention - though that can be prioritised for the tree's sake where there's a risk of mechanical failure."
Such failure may be a particular danger on old pollards, he says. "Cutting may have been out of cycle for decades or even centuries."
The legal mainstay of tree protection, the Tree Preservation Order (TPO), is of limited use for ancient trees, he says. "They can still fall foul of the 'dead, dying or dangerous' disqualification."
A step has already been taken towards greater protection of historic trees in Scotland. The new planning bill, currently before the Scottish Parliament, revises the provisions for TPOs, allowing trees to be preserved on the basis of their historic and cultural, as well as amenity value.
According to arboricultural consultant and author Donald Rodger: "It's a sea-change and has come about thanks to pressure from groups like the ATF. But it's not the be all and end all - they are still at risk from neglect, development and ill-informed management. They may still get butchered and don't have the same vigour as a young tree to recover."
Fortunately, the guidance available to practitioners has also improved in recent years with a manual produced by ATF co-funder Natural England, The Veteran Tree Management Handbook, widely in use.
According to Natural England forestry and woodlands officer Keith Kirby: "The profile of ancient trees has increased over the past 10 years. And thinking has evolved on how you manage trees, in terms of pruning, reducing weight, preventing splitting and also managing the landscape around them - for example by 'haloing' or clearing competing young growth from round them."
Grazing, he points out, can reduce competition from other vegetation, but can also lead to compaction as herds seek shelter under ancient trees.
Other threats Kirby points out include overshading, pollution, climate change and with it the potential for exotic pests. "Phytophthora or oak processionary moth could be a real problem if they got established in our oak population," he says.
He adds that a common-sense approach is needed on the issue of risk. "Individual people are not a problem, though it's not advisable to picnic under one of these trees on a windy day."
The National Trust is thought to be the country's largest single owner of ancient trees, and has recently appointed a dedicated ancient tree officer. Head of forestry and ATF board member Ray Hawes says: "The forum has opened the eyes of the ordinary tree manager to their value, which they pass onto their owners."
This has in turn affected training and practice in the arboriculture sector, he says. "Things like risk assessment are not an exact science, but there's a lot more knowledge now. In the past you would just have chopped bits off to make them safer. Now it's looked at more holistically - does adaptive growth outweigh the process of decay?"
High-tech equipment such as thermal- imaging cameras is helping practitioners make better-informed decisions, he adds - decisions have to be traded off against the demands of public access.
"Sometimes you have to reduce the occupancy rate around trees, by making it slightly more difficult to get there," he says. "You might change a path to go around rather than through the middle of them. And sometimes you have to do a little work to reduce the risk to an acceptable level, as well as for the good of the tree."
HUNTING FOR HERITAGE
Run by the Woodland Trust, the Ancient Tree Hunt is currently halfway through its five-year programme to record as many of Britain's ancient trees as possible. A website cataloguing these has been live for a year.
Already more than 30,000 trees have been logged, says programme manager Nikki Williams, who adds: "We're on target for 100,000 by 2011."
As well as simply recording the trees, the programme aims to support owners with their management and maintenance, and help prevent their loss. "If tree officers know that a given tree is on the website, they will look on it more favourably," says Williams. "It will also help monitor the effects of climate change."
According to the ATF's Neville Fay: "It has brought in new trees that lie in fields, parks and gardens that we never knew about. They turn out to be all over the place - from churchyards to cliff faces."
Results can be viewed at www.ancient-tree-hunt.org.uk