A year after the first case of ash dieback in mature woodland - and with the disease spreading inexorably - experts are looking at ways to future-proof forests.
Stroll around the Woodland Trust's Hucking estate (pictured in satellite views, above) near Maidstone in Kent and you could be forgiven for thinking little has changed in centuries.
Sheep graze on the swathes of grassland between the gentle chalk hills. Pockets of ancient woodland carpet the hilltops and valleys.
In reality, however, this seemingly timeless rural landscape is in constant flux and the effects of ash dieback will soon be all too apparent.
Trees on the estate show the hallmarks of the disease in the black, shrivelled leaves hanging from the branches of diminutive seedlings and the magnificent ash trees that tower above.
Ash dieback is spreading fast in this Area of Outstanding Beauty known as the Kent Downs, with trees bearing the scars of the chalara fungus.
"See that lovely big ash up there," says site manager Clive Steward, pointing out a huge tree in a patch of ancient woodland. "Underneath it - see the big wide leaves - that's sycamore. It's just waiting to take over really. Because that's what will happen."
Nature is poised to fill in the gaps if - as experts predict - millions of native ash trees die.
Britain's forests have been through much turmoil in modern times, from the harvesting of timber for the shipbuilding industry to the arrival of pathogens such as Dutch elm disease in the 1970s. But the current speed of change is alarming ecologists. They say trees are facing unprecedented threats, with a recent increase in findings of new pests and diseases.Trees, pests and how they have spread Continue reading the main story
Other major threats
• Dothistroma needle blight - a fungal disease that causes mortality and loss of timber yield in pine trees.
• Great spruce bark beetle - present throughout much of the Eurasian region, practically everywhere that spruce trees grow; discovered in UK in 1982.
• Oak pinhole borer - once rare in Britain, but populations grew in the south after the 1987 gales.
• Phytophthora alni - Lethal disease threatening alder trees - first discovered in UK in 1993.
• Phytophthora austrocedrae - Confirmed as the cause of dieback and deaths of juniper bushes in Northern England in 2011.
• Phytophthora kernoviae - confirmed only in Britain, Ireland and New Zealand, and only in a few trees. Can infect beech and oak.
• Phytophthora lateralis - usually kills most Lawson cypress trees that it infects. First recorded in the UK, in Scotland, in 2010; now present in Devon, Yorkshire, Northern Ireland and Republic of Ireland.
• Phytophthora ramorum - a fungus-like organism which attacks many trees, including larch.
• Pine tree lappet moth (Dendrolimus pini) - found breeding in Inverness-shire pine plantation forests; can be a serious defoliator of pines and other conifer trees in some parts of its native range in Europe and Russia.
Source: Forestry Commission
Many believe it is only a matter of time before threats such as the emerald ash borer beetle, which drills into the trunks of ash trees, reach our shores.
In an age of global trade and travel, rather than trying to stop these invaders, the key to safeguarding forests could be to closely manage them - and plant them to be resilient to future threats, be they a new pest, a violent storm, or climate change.
Austin Brady of woodland conservation charity the Woodland Trust says to give a wood resilience a range of native species need to be planted, so if a pathogen strikes, at least some of the trees will survive.
"For future healthy forests we need forests to have a wider range of native species growing there, so that all our eggs aren't in one basket," says Mr Brady.
"So that if a particular pest and disease or issue comes along it won't destroy the whole forest. It might take out some of the components but there'll be enough different species of trees in there for the forest to survive."
Maintaining diversity in the age of trees is also important, he says, as is maintaining connections between woods to give wildlife the space to thrive.
The Hucking estate is seen as a pioneer of the idea of resilient woodland. A few decades ago, before the estate was taken over by the Woodland Trust, much of it was arable farmland, dotted with patches of ancient woodland.
Careful management and planning has restored the natural landscape, with new trees planted to create corridors of habitat for animals and birds to roam. A mixture of native trees were used, which stand a better chance of withstanding tree diseases that are moving around the world.
Mr Brady sees the practice as trying to "mimic nature".
But some believe management in this way is artificial, and that nature will find its own level.
Naturalist and writer Richard Mabey argues catastrophes like tree diseases are natural events, from which woods will recover without intervention.How new planting will change the Hucking estate Continue reading the main story
- Before: The top image shows how the ancient woodland on the Hucking estate was fragmented when the Woodland Trust acquired it in 1997.
- After: The bottom image shows how the Hucking estate should look in the future. Seventy-eight hectares of new broadleaved native woodland has been planted to link up the isolated blocks of ancient woodland. This expands their core area to give the habitat greater protection from external environmental factors to help maintain stable conditions within the woodland.
"Woody vegetation responds, adapts, regroups," he wrote in the New Statesmen. "What emerges in its recovery stage may not be the same as before, but it will always be a vital, dynamic, arboreal community. The same process will happen with ash, perhaps more quickly than we think."
Joan Weber of Forest Research, agrees that "nature will fill in the gaps," as it did when elms disappeared, but this is more difficult when one particular species is dominant in a woodland.
Austin Brady, however, says Britain's countryside has lost the great, untamed forests still present in countries such as Poland, with a corresponding loss of diversity.
"You could make an argument for saying, let's leave forests to nature," he says. "The trouble is - we stopped leaving forests to nature in this country about 2,000 years ago. So we can't suddenly now say let's leave them to nature... we've taken away all the support systems that nature would have had in place."
Others question exactly what resilience means. Managing a wood land to guard against the effects of tree diseases will not necessarily help other wildlife in the area, says Ray Dawes of the National Trust .
"If you are going to change the tree species you are going to change the wildlife," says Mr Dawes, who believes the prescription for a healthy woodland varies. The National Trust has 400 properties with significant amounts of woodland in England, Wales and Northern Ireland, and they are all different.
"It's looking at individual woods - their origins, their values and the threats to them," he says.
Ash dieback: A spotter's guide
Back at the Hucking estate, Clive Steward spreads out an ordnance survey map over the bonnet of his dusty estate car to point out lanes in the Sussex and Kent weald that were carved by ancient farmers running pigs through the forests. Ash trees have left their mark on the map, recorded in names like Ashford and Asholt Wood.
Local conservationists are preparing to record the impact of the ash tree on the landscape from a cultural perspective, in case it is lost.
Nick Johannsen, director of the Kent Downs Area of Outstanding Natural Beauty, grew up during the era of Dutch elm disease, and remembers it well.
"It's going to be a longer, slower, more lingering loss than elm was," he says. "But already beautiful ash trees are a shadow of themselves."
Ash has long been part of our heritage, he says, used for the framework of early aircraft such as the De Havilland Mosquito, and tennis racquets at Wimbledon.
"Not only is it extraordinary in its landscape and its wildlife importance - its natural heritage - it's also part of the cultural heritage of Britain. That's what we want to celebrate - because we are losing ash trees."