Ash dieback could devastate Britain’s landscape
Name an iconic tree species for Britain … Did you answer oak or Scots pine? My guess is that it was one or the other. There is another species however that holds a unique place in British landscapes, not just in lowland forests, but in our uplands, in wet woodlands, among hedgerows and fields, in streets, parks and gardens – the ash Fraxinus excelsior. It may not demand our attention in the same way as some other tree species but it is extremely valuable and important in so many ways.
Take a look at the distribution map (right) for ash – every blue dot represents a 10×10km square in Britain where ash is present. Very few places in Britain are without ash trees. It is a vital component in the ecosystems of many mixed woodlands, being an ideal companion to oak and other hardwoods. It regenerates readily being adapted perfectly to the British climate. Its wood remains one of the best materials for sporting goods, makes beautiful furniture, while its properties for firewood are unrivaled.
Imagine therefore a scenario where ash may disappear from our landscapes. Horrifying – yes; a reality – quite possibly.
Readers may have picked up the worrying news that during an official inspection carried out in February 2012, symptoms of ash dieback were observed on Fraxinus excelsior in a nursery located in southern England. Suspect symptoms were identified in a batch of 600 plants which had been imported from the Netherlands in November 2011. The presence of Chalara fraxinea (EPPO Alert List) was confirmed on the basis of the morphological characteristics of the pathogenic fungus. Eradication measures were put immediately into place and the infected lot of F. excelsior was destroyed. Further investigations on the site revealed suspect symptoms in other Fraxinus species which had also been introduced into the nursery in November 2011. Investigations have been carried out to trace-back all Fraxinus consignments originating from the same Dutch supplier which had been imported into the United Kingdom, as well as to trace-forward all plants from the infected lot which have already been sold by the British nursery.
In Denmark, around 90% of all ash trees have been affected by Chalara fraxinea, and it is rampant across northern and central Europe. Young ash trees are particularly vulnerable and can die within one year, while older trees although capable initially of surviving the dieback, are likely to die after two or three consecutive years of infection.
According to the official line (see links below) the fungal disease has not yet been found in the natural or wider environment in Great Britain, that is, outside nurseries and recent plantings. My guess is though that it is already loose and rampant in our landscape. History tells us that we usually become aware of serious pests and pathogens late in the day. Pests and diseases can appear and then take time to impact too. For instance, Dutch elm disease was first detected in Britain in 1927, and was probably present before then, yet it was not until the 1960s that millions of elm trees were affected by the disease and mature elm trees wiped from our landscape.
Chalara fraxinea is being treated as a quarantine disease under national emergency measures, and it is important that suspected cases of the disease are reported. See the links below to aid in identification.