Invasive non-native species cost the Northern Ireland economy an estimated £46 million (€53 million) annually, according to recent figures.

A nest of Asian hornets was discovered and removed in Dundonald, County Down, last October. The Northern Ireland Environment Agency led the response, assisted by the UK Animal and Plant Health Agency and a specialist from the National Biodiversity Data Centre operating under the Shared Island Biosecurity and Invasive Species Initiative.

The UK-wide cost of invasive species totals around £2 billion (€2.3bn) per year. Globally, they are among the top five drivers of biodiversity loss, alongside habitat destruction, pollution, climate change and direct exploitation.

Grey squirrels, descended from 12 individuals introduced in County Longford in 1911, are now common across Northern Ireland, including in urban centres such as Belfast. They compete with native red squirrels and carry squirrelpox virus, which is lethal to reds.

The British-Irish Council is supporting cross-border work through Invasive Species Week, running from June 22 to 28. Events across Ireland and the UK include non-native species identification training and park sweeps.

Recovery of the pine marten, a native predator, is helping control grey squirrel numbers. A sighting in Dundrum, County Down, highlighted the species' return. Pine martens more easily catch heavier, ground-foraging grey squirrels, and their comeback has coincided with red squirrel recovery in some areas.