I was nine when I first saw a squirrel in the flesh. Several, in fact – a troop of red squirrels watched on as we had a picnic under the trees in Greenwich Park during the blisteringly hot summer of 1995.
Now, I might see a dozen in one day at the park or greenway, and, increasingly, on the street. But these are not the timid red squirrels of my youth, which generally eschewed human contact. They are grey squirrels that sit imperiously on fence posts, raid bird feeders, and launch themselves across the road with a sort of casual recklessness that still makes me nervous no matter how often I see it happen.
According to genetic analysis published in 2016, very nearly every grey squirrel now living in Ireland is descended from a population of twelve introduced in the summer of 1911. These squirrels arrived as a wedding gift at Castle Forbes in Co Longford, drawn from the celebrated collections at Woburn Abbey, which was at that time a hub of fashionable Victorian and Edwardian experiments in acclimatising exotic species to European soil.
From Longford the population spread outwards at roughly three kilometres a year, colonising first the eastern midlands, then the rest of Leinster and on to Ulster. Within a century they were firmly entrenched in Belfast. The native red squirrel is smaller and lighter and unable to compete for the same broadleaf forage. Worse, the greys carry a squirrelpox virus to which they are themselves immune but which kills reds within weeks.
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By all accounts, the Forbes squirrels arrived to polite applause. A more recent arrival has generated official alarm. The Asian hornet has been expanding across continental Europe since it stowed away in a consignment of Chinese pottery delivered to Bordeaux in 2004. Sightings in Co Cork last year prompted a rapid response and the destruction of two nests. Only last month the Government announced a new Invasive Species Bureau, jointly run by the National Parks and Wildlife Service and the National Biodiversity Data Centre in Waterford, and published a roadmap based on what it learned from the Cork experience.
[ Bureau to tackle invasive species set up in WaterfordOpens in new window ]
Last October, a nest was found in Dundonald, a stone’s throw from where I grew up. It too was removed, in an operation led by the Northern Ireland Environment Agency, supported by the UK’s Animal and Plant Health Agency, and featuring on the ground advice from an official from the National Biodiversity Data Centre through the Shared Island Biosecurity and Invasive Species Initiative. All-island co-operation is essential to biosecurity, not least because invasive plants and animals are indifferent to which side of a line that runs between Belcoo and Blacklion they are on.
The British-Irish Council is also supporting this cross-Border collaboration with Invasive Species Week, which falls from June 22nd-28th. There are events across Ireland and the UK such as non-native species identification training, national park sweeps, and a series of webinars. Invasive non-native species drain about £2 billion (€2.3bn) a year from the UK economy and around £46 million (€53m) from Northern Ireland alone. Globally, they sit among the top five drivers of biodiversity loss, alongside habitat destruction, pollution, climate change and direct exploitation.
In Ireland they include Rhododendron ponticum, the Victorian ornamental plant strangling the oak woods of Killarney; zebra mussels, which have colonised inland waterways; the American mink, escaped from fur farms; and the infamous Japanese knotweed. Sika deer, brought in as park ornaments in the Victorian period, are now hybridising with the native red deer to the point where genetic purity is difficult to identify. Bank voles, which arrived in the 1920s in the soil clinging to Siemens earth-moving machinery imported through Foynes for the construction of the Ardnacrusha dam, are now established across most of Munster.
The good news is nature often fights back with surprising power. The European pine marten, a slim, tree-climbing native predator that was itself almost extirpated in the 20th century, has been recovering across the Irish midlands and in woodland areas further afield. I happened to spot one in Dundrum, Co Down, last year; they are astonishingly quick and agile. Pine martens will, given the chance, eat a red squirrel. But they find greys easier prey for exactly the same reasons that greys have out-competed reds; they are heavier, slower, less cautious, and more often found foraging on the ground. Wherever pine martens have re-established themselves in numbers, reds have begun to return.
This is a delicate piece of ecological balancing, and it’s one entirely outside the influence of any Government roadmap, although that probably shouldn’t stop us trying.
Stuart Mathieson is research manager with InterTradeIreland
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