Extreme Weather: Woodland Management in a Changing Climate

Nick Gibbs
Monday, 24th February 2014

The wet and stormy weather this winter has had huge effects on our woodlands. Nick Gibbs, editor of Living Woods Magazine, explains how climate change has an impact on future woodland management and how we can adapt to the greater extremes.

Storms and heavy rainfall have devastated southern England, and indeed much of Europe in the winter of 2013-14. Trees have come crashing down, reportedly killing more than 15 people across the continent this winter, and though trees generally cope well with flooding, we have to start planning for this to become a more regular weather pattern and owners have to understand their responsibilities. If there is any good news, amidst the devastation of trees crashing to earth, it is that woodland is a greater part of the solution than the problem.

The sensible thing for owners of trees in these wet times is actually to do as little as possible. The Forestry Commission recognises that woodland owners will be concerned that their trees may not survive prolonged inundation. "Much depends," an FC spokesperson has said, "on factors such as the species of tree, the duration of the flooding and the depth of the water. However there are reasons to expect that most mature and semi-mature trees, especially broadleaves, will recover from the current episode, including the fact that trees withstand flooding better in winter, when they are not active, than at other times of the year." Experts acknowledge that some replacement planting may be needed, especially of young, small trees which have been submerged for a prolonged period, and some trees' ability to withstand pests and diseases my have been impaired.

Getting stuck in the mud and damaging the ground are the most likely consequences of entering woodlands in the wet, but Director of the National Coppice Federation, Toby Allen of Say It With Wood, is also warning of the dangers of trying to clear up trees affected by storms. "Whilst it is important these trees are attended to," he says, "people must understand the dangers involved and how to deal with the problem safely and effectively." Windblown trees are some of the most dangerous to resolve, often hung up on others, and as a consequence referred to as 'widow-makers'.

We may not be able to clear up today's mess immediately, but we can now expect these wet, warm, windy conditions winter after winter, and so we have to consider what can be done for the future. "What we have to get our heads around," says the Forestry Commission's Woodland Creation Consultant John Weir, "is that this sort of winter is what we've got to expect."

Though some tree species thrive in wet conditions, it is the threat of drier summers that is determining the planting plans of foresters. Trees hibernate in winter, just like wildlife, and their roots can survive sleeping in the damp. Though some species like alder, willow and poplar thrive in wet conditions, and are often planted in the sodden corners of farmland that can't be cultivated. However, it is their ability to cope with drier summers that defines which trees we should be planting with climate change in mind, and we don't have to look that far afield says John Weir of the Forestry Commission: "The main message is to look for native species that reach across Europe, selecting seed from provenances 2-5° south of their current location, with the same relative position to the Atlantic for a similar climate."

That's not to say we shouldn't be planning for winter as well. Indeed if the weather patterns we are currently experiencing do continue then our forestry practices as well as species selection may have to change.

It's all a question of seasons. Winter in the woodlands is generally considered a time for human activity. Trees are more likely to recover from pruning and coppicing that's done when they are asleep, felled trees in winter comprise considerably less moisture to remove for timber or firewood, and with a bit of luck the ground is frozen so that machinery won't cause so much damage. Wildlife is less likely to be disturbed during critical breeding periods in winter, and woodlands containing protected species like dormice cannot be worked once hibernation ends.

Extraction of logs by horse is already returning to woodlands, and the prospect of wetter woodlands is likely to bring more work to horse loggers who pull out stems by harness. Horses can work on wetter ground than large machines, and cause far less damage. The New Forest National Park is one of many organisations to embrace horse logging, and have been running courses to acquaint owners and woodland managers to the benefits of timber extraction that way. "The advantage of working with horses to extract felled trees from woodland," says Caroline Wilkins, who attended one of the courses this winter, "is that they barely disturb the woodland floor. The difference is phenomenal and this has to be a good thing for the environment and woodland biodiversity."

The Forestry Commission revealed recently that some 70,000 woodlands in southern England were affected by the St Jude storm in October 2013. "In hard numbers," said Richard Greenhous of the Forestry Commission, "this could account for 10 million trees 'lost' from the woodlands as a result of this natural event, but we must remember that more than 650 million remain. The trees around and below those that will die or are damaged will compensate for this loss and will grow into the gap left in the canopy. During that time additional light will reach into the forest encouraging ground flora and wildlife in general."

Wetter roots are likely to make trees more unstable, and with windier weather there will be more windblown trees. This will demand more careful thinning, perhaps earlier when trees are less susceptible to being blown over from being too tall and spindly. In Kent, woodland owner Margaret Johnson, who was recently awarded a Gold Star in the Sylva Foundation's Woodland Star Rating scheme for the management of her woodlands, lost two acres of conifers which had recently been thinned but were all knocked over by the recent storms. "It's a gamble on the wind for a few years," says John Weir, "if you leave trees for 20 or so years before thinning."

The effects of recent storms are certainly not confined to southern England, let alone Britain. The Danish forest-owner association, Dansk Skovferening reported that there was probably 1.08 cubic metres of storm-damaged wood in last year's October and December storms.

Because her trees have fallen in one concentrated area, Margaret Johnson may be able to get her regular horse-logging contractor, Frankie Woodgate, to extract the trees. However, some stems will be damaged and most have fallen haphazardly, so the extraction, even by horses, will be costly and the timber may not be of great value. "Windblown and snapped trees were generally very thinly distributed across woods," says Richard Greenhous of the St Jude storm, "so harvesting this material would be uneconomic and most will be left in the woods. The dead tree left behind by the storm will contribute to deadwood stocks in the forest and this will be a bonus for biodiversity, providing additional food sources and breeding habitats for flora and fauna such as lichens, fungi and invertebrates."

Woodland owners do, however, need to consider the risks to walkers inside their woodlands, and particularly if their woods border roads. Drivers may have noticed more ivy-clad trees falling onto the tarmac this winter than normal, with the creeper enjoying warmth, damp and light in the verges, where it weighs down dead or dying, and almost certainly unmanaged trees. "The owners of trees alongside roads, footpaths and car parks, whether public or private, have a duty of care to users of those places," a Forestry Commission spokesperson told Living Woods magazine. "We have a system for inspecting such trees on the public forest land which we manage, and carry out preventative felling or pruning as required. We strongly recommend that other owners do the same. Guidance has been published by the National Tree Safety Group."

According to the Highways Agency (who are only responsible for motorways and trunk roads), it is county councils that will be feeling the brunt of roadside tree problems, dealing with ivy-clad trees close to roads. Adrian Wood, Countryside Service Tree Inspector for Derbyshire CC agrees that ivy is likely to be a growing threat to roads with warmer, wetting winters: "Obviously one of the reasons for [tree] failure will be due to decay from fungal infection. Ivy can often mask this, so we have to be thorough during Highway Inspections. Ivy is enjoying the climate so is growing quite nicely all year round, and in many cases outcompeting trees which are more often than not stressed due to other factors. This leads to a significant 'sail area'. In the winter months, when typically deciduous trees are not in leaf, the trees will have a 'full crown', and this coupled with the waterlogged ground has meant more failures."

The irony is that trees are good for retaining moisture in arid conditions, for reducing erosion from rainfall, and as a defence against deluges. As Marie-Claire Kidd writes in the March/April 2014 issue of Living Woods magazine: 'There are moves afoot to increase the size and quality of Yorkshire's wet woodlands, in a bid not only to manage a rich and rare habitat, but also to alleviate flood risk.' She spoke to Yorkshire Wildlife Trust Manager Nick Simms, who says: "Wet woodland is good at storing floodwater. This means that when water levels rise, this habitat can help prevent it reaching our towns and villages."

Yorkshire Wildlife Trust are looking to plant more species like willow, alder and birch, and John Weir at the Forestry Commission agrees. "Why have we ignored alder?" he asks. "Old black poplars have not been fashionable, and why not push conifers towards the wet and marginal soils? Sitka spruce is very windfirm unless thinned too late. And what about swamp cypress?" He has been tasked by the Forestry Commission to question and debate the species we select, and to getting foresters and woodland managers or owners discussing alternatives to the likes of beech, which is shallow rooted and vulnerable to squirrel attack, and which is unlikely to thrive in the future.

Woodland owners and organisations are having to rethink the way we stock and manage forests and woods. The Institute of Chartered Foresters has been running seminars around the country looking at alternative species to plant and the Royal Forestry Society (RFS) has recently added a Woodlands for Climate Change Award to their prestigious annual Excellence in Forestry competition. "The purpose of this award is to encourage and recognise tree plantings," says Trefor Thompson of the RFS, "both new and restocking, that create woodlands that are resilient to the predicted challenges of climate change and pests and diseases." We will all be watching the winners with growing interest.

Nick Gibbs is the editor and founder of Living Woods Magazine.

This article appears in our new Woodlands and Outdoor Living newsletter. Sign up here to receive monthly updates! 

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