Japanese knotweed and other invasive species cost UK £4bn a year, research suggests

Ash dieback most expensive, while cost of tackling alien species has more than doubled since 2010, says study

From Japanese knotweed to a fungus that kills ash trees, tackling invasive non-native species now costs the UK economy about 4bn, up from 1.7bn in 2010, research suggests.

There are about 2,000 invasive non-native species (Inns) in the UK, and about 12 new ones establish themselves each year, adding, along with inflation, to the rise in costs.