Storm Arwen came hurtling down from the north at the end of November, causing a tsunami of trees to crash to the ground across Scotland, northern England and parts of Wales. Winds of 100mph flattened conifer plantations like dominoes; large country houses lost 250-year-old oaks; and gardeners grieved for uprooted magnolias and rhododendrons. Three people died and more than 9,000 were left without power for more than a week in bitterly cold weather. Phones were down, roads were blocked and people had trees coming through their roofs. “You weren’t going anywhere,” remembers Heather Swift, the Woodland Trust’s Cumbria site manager, who has been assessing the tree damage in the area. Storm Arwen has brought about dramatic changes in the landscape, but such upheaval also presents an opportunity to increase forest diversity, expand the provision of wildlife-rich dead wood and create more variation within plantations, say experts. “We think they’re disasters, and momentarily they are, but in the grand scheme of things, this is natural,” says Swift. Many compare the damage to the “great storm” of 1987 that ravaged the south-east of England and London when 115mph winds uprooted 15 million trees, except Arwen seems to have attracted less attention, perhaps as it affected less populated parts of the country. “It was similar in terms of scale of damage, the disruption it caused and size of trees that went down,” says Swift. “There have been some mighty fine trees that have gone down, and there was nothing wrong with them. Huge, beautiful oaks just laid flat on their sides.” Estimates suggest that 8 million trees have been affected in Scotland and 4 million in England, although it will take weeks to work out the full extent of the damage. Currently there are no estimates available for Wales. The National Trust is the largest single custodian of ancient and veteran trees in Europe, and for some properties in the north of England, this was the worst storm in 40 years, with an estimated £3m in damage across sites nationally. Staff were left devastated after losing trees and gardens they’d spent whole careers looking after. “To lose so many in such a short period, I think that’s what is so heartbreaking … Trees are just as important to many of our properties as historic buildings and collections,” says John Deakin, head of trees and woodlands at the National Trust. More than 50 trees were uprooted at Bodnant Garden in Conwy, including the tallest redwood in Wales, which stood at 51 metres and was expected to reach double that height. The Wallington estate in Northumberland saw half its veteran trees blown over. Storm Arwen had a disproportionately large impact on trees because it came from the north, rather than the south-west, which is the prevailing wind direction. Trees are adapted to withstand winds piling in off the Atlantic by anchoring their roots in a specific way and putting on wood in particular places. Woodlands also naturally have smaller trees on the south-west so they are more aerodynamic in strong winds, but this means they are ill-prepared when the wind switches direction and they are battered square on. After the 1987 storm (which did come from the south-west) there was a rush to clear away all the fallen trees, but conservationists say the mess left behind transformed our understanding of woodland ecology, highlighting the benefit of diverse, scruffy, open habitats within woodlands. The response to Storm Arwen will be different from the 1987 storm, and as many fallen trees will be left as possible, say conservationists. “It’s now part of our cultural and historical landscape – clearing it all up kind of obliterates the memory of it,” says Swift. She plans to reroute footpaths around some fallen trees, rather than removing them. The National Trust will leave fallen trees if they are not negatively affecting tenants or posing a risk to visitors, seeing the stricken lumber as another chapter in the story of their properties. This could have significant biodiversity benefits. In wild, natural woodland a quarter of wood is dead, but in most managed woodlands this is less than 10% as people clear it away. The aftermath of Storm Arwen is an opportunity to leave dead and decaying wood in situ, creating rich and underserved wildlife habitats as a result. “We really have a history of overgardening, perhaps seeing some of these natural habitats as untidy … We’ll leave as much [dead wood] as we possibly can,” says Deakin. Storm damage creates opportunities to build more structure and diversity into woodlands in a way that might not have happened before, he says. High winds are likely to hit the UK more frequently and with more strength as the climate crisis goes on because warm air holds more moisture which fuels storms, and so these rare events will become more common. Conservationists and foresters are working out how they can reduce the damage when the next storm hits. The National Trust is looking to move towards more natural tree management. Ancient oaks, for example, lower their branches as they age to make themselves more stable. Sometimes people might overplay the need to take limbs off trees from a health and safety perspective, but the risk of being hit by a fallen branch is incredibly low, says Deakin. “Overzealous intervention is not going to do a tree any good at all. It’ll make it more susceptible to many different factors of which storm damage is one.” Many trees that were knocked down were single-species, single-age conifer plantations, which are more vulnerable to storms than native, mixed woodland. “Over the next 50, 100 years, the forests we’re producing now will be much more diverse … They’ll be better adapted for Storm Arwen-type events and more generally climate change,” says Doug Howieson, Scottish Forestry’s head of operational delivery, who has been working with trees since the 1987 storm. The benefits of work being done since Storm Arwen will be seen in decades to come. “The trees that we plant today, we will not see mature, but people in the future will appreciate our work,” says Howieson. In the meantime, forestry and conservation organisations are urging the public to stay away from damaged trees as they can be dangerous.