Stephen Moss. Wednesday 23 March 2016.
Reports that the ash tree is “set for extinction in Europe” have sent a shiver down the spine of everyone who loves and values Britain’s trees. For older readers like me, the stories are an unwelcome reminder of 40 years ago, when another familiar tree – the English elm – was devastated by Dutch Elm Disease.
The new research, published in the Journal of Ecology, paints a grim picture for the future of the ash in Britain and Europe. The trees are suffering a twin-pronged attack: from ash dieback, a fungal disease also known as Chalara, and the invasive emerald ash borer beetle. It has yet to reach the UK, but is moving westwards across Europe at a frightening rate.
The disappearance of ash trees would not just affect our landscape, especially in lowland Britain, but also the 1,000-plus species that depend on the ash, including more than 200 different invertebrates. But is this yet another story that might not be quite as clear-cut as the headlines suggest? Some, including naturalist and radio presenter Brett Westwood, are cautious: “I’m not certain that this will mean total wipeout of the ash in Britain, because it has strong genetic diversity which allows more chance to evolve resistance. There’s evidence that younger trees in nurseries, many of them grown in continental Europe, are more vulnerable and that fewer of the mature British ashes are displaying symptoms. Nevertheless we should be very alarmed that there is a serious risk of losing such an important and conspicuous species from our landscape.”
The doyen of tree experts, George Peterken, agrees. “There is genetic diversity in ash, and I would expect them to evolve their way round the fungus,” he says. “Even so, I endorse [ecologist] Oliver Rackham’s warning that globalisation is the main threat to British trees – from imported diseases and introduced mammals.”
The more urgent question is what humans can do to slow the progress of ash dieback. First, we need to spot any infected trees: by looking for a distinctive blackish-brown tinge towards the ends of the leaves, or lesions on dead or dying shoots. If you do find what might be signs of the disease, you should report them immediately to the Forestry Commission.
If these threats are to be beaten in the longer term, we need to stop imports of ash saplings from Europe, and identify any resistant trees that might provide a reservoir of seeds for future planting. We could also plant alternative native tree species that can fill the niche left by the loss of the ash. We won’t know whether any of these measures have worked for many decades – by which time there will no doubt be many other threats to Britain’s beleaguered trees.
Stephen Moss’s Wild Kingdom: Bringing Back Britain’s Wildlife, is published on 7 April (Square Peg, £16.99)