A fungus called Hymenoscyphus fraxineus, also known as Chalara ash dieback, is wreaking havoc among ash trees in the Netherlands and foresters fear that in the worst case scenario 98% of all ash trees could die, the Volkskrant reports.
The Chalara fungus, which is thought to have come into the country from Asia via Poland and the Baltic states around 2007, causes leaf loss, crown dieback and bark lesions. Once a tree is infected it will die, either from the fungus or because it has become more vulnerable to other pests, such as honey fungus.
It took until 2010 for the fungus to affect large wooded areas in the north of the country but it wasn’t until 2016 that a major epidemic broke out, the Volkskrant writes. Germany, Britain, Belgium and France are also faced with ash dieback.
There are around ten million ash trees in the Netherlands and 80 percent of the ash tree population under the management of Staatsbosbeheer Nederland is thought to be affected by the fungus to a greater or lesser degree.
Large numbers of sick trees have already been cut down in the main problem areas of Flevoland, Groningen and Zuid-Holland. Next week trees in Gelderland and around Amsterdam will be cut down, the paper writes.
Staatsbosbeheer is expecting to spend €10 to €20 million on cutting down affected trees and planting new ones. The organisation is responsible for a third of all ash trees in Dutch forests which means costs can go up to €60 million, and that is not counting the loss of revenue from the wood, which is used for tools and children’s play installations.
European estimates put the survival rate of the tree between 2 to 30 percent. ‘It will become rare,’ Wageningen University tree expert Jelle Hiemstra told the paper. Paul Copini of the Dutch Centre for Genetic Resources thinks the trees have a 2 percent chance of survival while Staatsbosbeheer rates its chances at 10 percent.
By trying to protect the stronger trees from the fungus foresters are trying to create a better – and perhaps fungus resistant – tree so that in a decade or two new trees can be planted, as happened with the elm tree which, after the epidemic of the seventies, is only now making a comeback.
Giving up on the ash tree is not an option. ‘There are dozens of organisms that depend on this tree. Certain types of mosses and insects are already struggling,’ Copini told the paper.
According to Hiemstra there is another reason why the tree should be saved. ‘It’s an indigenous tree which belongs in the Dutch landscape. We have become very attached to it,’ the Volkskrant quotes him as saying.