Effects of the disease

The sheer abundance of the tree means that loss of ash will have a major impact on the environment as well as on the economy. Diseased trees pose a safety hazard in high risk areas such as along highways, and road closures required for tree removal could cause disruption affecting people and businesses.

Effects on Devon’s environment

Unless ash trees lost to disease are replaced with other species quickly we can expect to experience an environment that is less resilient to climate change, and which supports less wildlife. Since ash trees are a key characteristic of many landscapes in Devon, their loss will degrade our countryside and towns, making them more featureless and less distinctive. Loss and damage of non-woodland trees will have a greater impact on landscape and biodiversity than that of woodland trees.

We can also expect to have to pay substantially more for some vital services that ash, along with other trees, provide naturally for free. This includes removing pollutants from air and water as well as reducing flood risk.

Effects on Devon’s economy

The particular characteristics of ash means that its loss will especially impact on timber production, on firewood availability, and on the production of specialist products like tool handles.  Employment and the rural economy will be affected.

Effects on landowners

Managing the effects of Ash dieback will require considerable extra work and expense for landowners and managers. Along Devon’s highways, private landowners are responsible for 99% of ash trees.

In addition there will be impacts on the function and economic value of any managed woodlands, especially of plantations with a high proportion of ash.

On the other hand, there may be an opportunity to achieve an income through the sale of ash wood, usually as fuel.  There may be a glut, reducing the price of firewood in the short term, but the overall trend is for firewood prices to increase

Effects on public bodies

As with landowners and managers, local and highways authorities will face significant increased expense, along with regulatory bodies such as the Forestry Commission and NGOs.

Ash trees in parks, schools, sports grounds and other public places, as well as those alongside roads, will need to be inspected more frequently than at present, and made safe as necessary, adding significantly to demands on public funding.

There will also be costs linked to issuing felling licences, handling cases where Tree Preservation Orders or Conservation Areas apply and responding to public concern. The cost of establishing replacement trees is also a concern.

Effects on public utilities

Electricity and telephone cables often run above and alongside hedges and other woody linear features.  Ash is also a frequent tree alongside Devon’s railways.

Ash dieback therefore poses a considerable risk to Devon’s power and communication networks: managing affected ash trees will be a major operation for the utilities and landowners concerned, adding both to costs and creating logistical challenges.

Effects on Wood businesses

Ash is a moderately valuable timber and an excellent source of firewood. The disease will render most ash trees valueless as a source of timber or other high-value products – they will be useful only for firewood unless the wood is processed before decay.

Some 97% of broadleaved woodlands in Devon (and Somerset) are in private ownerships as opposed to being managed by the Forestry Commission, so the impact will be felt very largely in the private sector.

Effects on Devon’s landscape

Ash trees along hedgerows near Dunstone, South Hams Copyright Mel Croll
Ash trees along hedgerows near Dunstone, South Hams Copyright Mel Croll

The impact of the disease on our landscapes could potentially be more severe than that of Dutch elm disease in the 1970s.  Although baseline information on the former prevalence of mature elm trees is lacking, ash is more abundant that elm ever was. over most of Devon.  While the rootstocks of most elms survive and continue to send up suckering growth, this is not true of ash: on the other hand, many otherwise healthy mature ash trees are likely to survive for many years, some perhaps indefinitely.

The impact on the hedged landscapes for which Devon is famed may be particularly strong.  The decline of mature ash trees, especially those which are isolated rather than within lines of trees, will exacerbate the loss of hedgerow trees already happening across the county, the number of mature specimens dying or being felled being greater than the number of young trees encouraged to grow as replacements.

Effects on Devon’s biodiversity

Across the UK, nearly a thousand species are known to be associated with ash trees, including birds, mammals, bryophytes, fungi, invertebrates and lichens.  Of these many are highly associated with the tree, and some are restricted to it.  Those species which are in the last category or highly associated with ash and already accorded threatened status are those at particular risk from dieback.  Of these, four fungi, four lichens, one moss, three moths and one beetle occur in Devon.  Assuming high levels of tree mortality, it is probable that one or two lichens will be at risk of extinction at a county level, while other obligate and highly associated species found in the county will experience large population declines.

The loss of ash, especially from woodland, is likely to have other, less direct, consequences for biodiversity.  The tree is especially notable for the rapid rate of decomposition of its leaves with a consequent high rate of nutrient recycling in stands where it is frequent.  A shift of woodland composition towards other tree species as a result of ash dieback is therefore predicted to result in slower nutrient cycling, greater carbon storage, changes in soil formation, and shifts in soil community with resulting changes in ecosystem function.

In practical terms, understanding which site-specific species and communities (e.g. of woodland ground flora) are likely to be adversely affected by ash loss will be important for woodland managers, so while retaining infected trees for as long as possible, they can choose appropriate replacement trees to plant or encourage.

Ash is a significant feature of many Sites of Special Scientific Interest and other places of particular nature conservation importance in Devon.  Natural England and the Forestry Commission have produced a guidance note for woodland SSSIs.

See Devon Action Plan for further detail on the likely effects of the disease.