A lesson from the recent pandemic - not that we should need it – is that tampering with nature’s equilibrium by introducing pathogens into places they weren’t previously can have devastating consequences. Since the dawn of primeval lifeforms, an ancient and complex battle has been waged across the planet. For every living creature has its enemies and allies, its stratagems and ruses to defend or attack.
While the cat and mouse play hunter and hunted, viruses propagate themselves by invading organisms’ cells, parasites constantly try to outwit their target host and a multitude of fungi and bacterium play either friend or foe, feeding some or devouring others. These skirmishes are the driving force for life on Earth, compelling the evolution of an unknowable number of species.
And although the links of the food-chain run up to mighty apex predators, they in turn can be felled by a microscopic sliver of viral DNA. In a healthy ecosystem, that has had millennia to reach a steady-state, the conflict leads not to victors and vanquished, but stable populations with no domineering species upsetting the status quo; that is until we came along.
In 2012 ash tree dieback disease (known as Chalara) was discovered in South-East England. Caused by a fungus Hymenoscyphus fraxineus which originated in Asia, it has very little effect on its native host the Manchurian ash. However, its introduction to Europe, through the import of saplings and timber, is devastating the European ash population.
Our native ash trees haven’t evolved with the fungus, this means they have no natural defence against it and year-on-year infections are slowly killing our ash population. In the UK we have a higher proportion of ash in our woods and hedgerows than continental Europe, and The Woodland Trust has estimated that we could lose up to 80 to 90 percent of them. This huge loss will change the landscape and threaten many species which rely upon native ash trees.
It is saddening to think that young naturalists, or those yet unborn, will experience a Britain with a relic population of ash, and probably accept it as ‘the norm’. They will not know the airy nature of the trees’ foliage that allows dappled light to dance on a woodland floor, the feel of the smooth grey bark. Even the trees’ sound as a breeze skips through the canopy will be lost.
The distinctive leaves of an ash tree hiss when they quiver in the wind, for a summer woodland has its own character made distinctive by the trees that form it. It has been said that ‘Oaks are leathery in tone, poplar fizz like the opening of a pop bottle and aspens have fooled many that rain is approaching.’ The woodwind section of nature’s orchestra may end up missing an instrument if we don’t act.
The spores of the fungus that infects ash trees is wind-blown. In the Norfolk Broads, for example, where the woods are particularly warm and humid the younger trees have terminally suffered. Although older trees, particularly the big ones in open areas, may survive longer - both due to them experiencing less exposure to spores and their size means they take much longer to die.
The hope is that some trees may hold immunity, if so, these individuals will provide the seeds for future re-planting projects. There is currently government funded research taking place, and the import of ash was banned in 2013. To call on a well-worn phrase, ‘the horse had already bolted’. To be fair, it is unknown how long the fungus has been in the UK, perhaps twenty years, as the slow progress of the disease made it difficult to identify.
We live in an expanding global economy and a shrinking natural world, and with poor bio-security, ill-thought-through species introductions and the continuing exploitation of wildlife we will see more diseases crossing continents. Due to poor wildlife welfare, viruses have infected, with devastating effect, species from totally different eco-systems. Let us try and make the new normal a valued and protected natural world, so wildlife is safe to do battle as nature intended.
Take action
Why not plant a native ash tree in your garden, local community green space or local wood? Or you could join a conservation organisation and help plant ash tree saplings. As the disease progresses, look for trees that have remained healthy, as it may be possible that they have immunity and you could think about collecting its seeds to propagate into small saplings for planting in your local area. It is always best to choose trees to plant with a local province. Our woods and ‘treescapes’ need to be diverse, in species, in structure and age but also genetically. This diversity is nature's best defence against future threats, known and unknown, of diseases, pests and climate change.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here