A wide range of ways to boost the resilience of Britain's woodlands were proposed at the Royal Forestry Society's and Woodland Trust's joint conference earlier this month.
Given the high level of uncertainty around the threats to trees posed by future climate change and novel pest and disease spread, "any single resilience approach carries a high risk of being the wrong fit", Scottish Natural Heritage land-use policy and advice manager Duncan Stone warned. "The more environmental change you assume, the more you have to change what you do," he said.
"Already in the last 30 years, the rate of forest pathogen invasions in Europe has escalated exponentially. Future pathogens will be able to migrate at a faster rate than tree species, while their ability to adapt to new climatic conditions will be greater than that of their long-lived hosts." A further wild card will be hybridisations between novel and existing pests and diseases, he added. "Phytophthora alni is a new species created this way."
According to Woodland Trust senior adviser Mike Townsend: "Right now we are failing to capture the value of trees, woods and forests, including the wider economic and social benefits." In addition to climate change and pests and diseases, further challenges to woodland are posed by deer and by development pressures leading to loss and fragmentation, he said. "The rate of change is significant and seems to be accelerating. There is no one solution (that can be applied) in isolation."
He added: "Boreal forests have low species diversity but are still resilient as they have broad variation in them. Genetic diversity within native UK species is generally high - they have the capacity for adaptation - and forests subject to high turnover tend to be more adaptive as disturbance creates opportunities for natural selection to take place." But levels of management, hence opportunities for regeneration, are low in the UK "while deer numbers are rising", he warned.
Potential risks of broadening range
Forest Research has drawn attention to the potential risks of broadening the range of timber trees grown in the UK, said Townsend, because not only can pests and diseases of imported species spread to native species, they may also become more virulent on their original host in a new growing environment, while native pests and diseases may also prove destructive to imported species.
He added: "There is increasing evidence of the role of trees in agriculture, in soil and water management and in livestock protection, but this isn't seen through in policy and practice."
Deer are also among the factors for a continuing decline in woodland species diversity, despite increasing woodland coverage, with more than one-in-ten of woodland flowering plants now on the national Red List, according to Wildlife Trusts England director Stephen Trotter. "The woodland specialists are the ones in trouble. Invertebrates in particular seem very responsive to climate change," he said, adding that "loss of connectivity" due to development, lack of woodland management and ageing tree stock are also contributing to the decline of some species.
"How do you bring new economic life into woodlands and realise their full value? If you can solve that issue we will have less of a problem," he said. Given that the social benefits from woodland are greatest near urban areas, he added: "We need good green belts. Most are boring. Let's plant them with trees and invest in these services."
Professor Dieter Helm, author of Natural Capital - Valuing the Planet, said a rigorous approach to valuing natural capital would boost the case for such changes in green belt use as well as fixing a value for urban tree stocks. "It's not a wishy-washy concept like 'sustainability'," he insisted. "A value on an asset represents the resources we should expend on maintaining it. Green belts are precisely where the economic benefits of public access are greatest. It's a massive opportunity to enhance the economic efficiency of the country now and in the future."
Forestry sector needs to up its game
Giving an industry perspective on economic resilience, Pryor & Rickett Silviculture managing director Graham Taylor said the forestry sector needs to "up its game", adding: "We have a high-tax, high-value economy so we shouldn't even try to grow low-quality conifers." While oak "always does well", he said: "Landowners find hardwoods too complex and bureaucratic." On financing, he urged: "Don't be grant-led as it skews your priorities. There's billions of pounds of private investment available."
Taylor said environmental organisations "take the view that timber production doesn't matter - we are here to deliver other environmental benefits", but that for the UK to import billions of pounds worth of hardwood timber "is ecologically unsustainable in global terms".
Successive ice ages have left the British Isles lacking in "trees of cold, wet, oceanic conditions", Forest Enterprise England head of planning and environment Jonathan Spencer said - a fate that western North America escaped. Proposing a "North West American Cool Temperate Forest Model" for upland timber production, he said: "Climate change and forest resilience are forcing a major rethink of what is native, what is natural and what might be wise."
Philippe Morgan, president of Pro Silva, which promotes continuous cover forestry internationally, said the continuous cover approach, in which trees are harvested selectively and regeneration partly occurs naturally, "simultaneously maximises the ecological and economic benefits of woodland". He added: "Natural selection will drive the forests of the future."
Woodland Trust chief executive Beccy Speight, chairing, said: "In other sectors companies do everything they can to stay relevant as their survival depends on it. Is all this an opportunity for us as well as a threat? A holistic approach, taking in economic, social and environmental factors, gives you a triple bottom line."