Financial impact per nation:
- England - £1.3 billion
- Scotland - £251 million
- Wales - £133 million
Plant species breakdown:
- Japanese Knotweed - £179 million
- Rhododendron - £9 million
- Giant Hogweed - £2 million
The research focussed on five case studies – Asian long-horned beetle, carpet sea squirt, water primrose, grey squirrel and coypu – with the impact of INNS on agriculture and horticulture estimated at £1 billion across the whole of the UK.
The case study into water primrose – a group of South American aquatic weeds – found that the eradication of the plant would cost approximately £73,000 but if it becomes widespread as is the case in France and Belgium it would cost £242 million to eradicate.
Defra minister for the natural environment Richard Benyon said: "Invasive non-native species have a significant impact on the British economy and damage our own wildlife.
"And the costs of controlling these species will rise unless society takes steps to prevent them taking hold and spreading."
Scottish Government minister for environment and climate change Roseanna Cunningham commented: "This report highlights that once established, invasive non-native species and animals and can have a serious impact and that early intervention not only has a beneficial effect on the environment but also on our finances."
Welsh Assembly Government minister for environment, sustainability and housing Jane Davidson said: "This report will help us to prioritise and target where actions can have the most impact, and will assist us in prioritising our resources for action in the future."