nvasive non-native species (INNS) such as Japanese knotweed and an ash-tree killing fungus are now costing the UK economy around £4 billion a year – up from £1.7 billion a year in 2010, research suggests.
Scientists said rising costs are partly due to inflation and new species establishing in the country.
The impact of alien species can range from loss of crops and damaged buildings to the loss of livelihoods and ecosystems.
The study, funded by Defra, showed the fungus Hymenoscyphus fraxineus, which kills ash trees, was the most economically damaging species over the past decade, costing around £883.5 million, followed by Japanese knotweed at £246.5 million.
Annual estimated costs in 2021 were £3 billion for England, £499 million for Scotland, £343 million for Wales and £150 million for Northern Ireland, according to the research carried out by international scientific organisation Cabi.
Other damaging species included rabbits – costing the UK economy around £170 million, rats and mice (£84 million), cockroaches (£69 million) and deer (£62 million).
It is vital that we work together with researchers, scientists and others, who are working to tackle INNS, to prevent their entry into and establishment in Great Britain and, when they do become established, to mitigate their negative impacts
The cost to forestry has increased eightfold since the previous report in 2010 and is now estimated at £123 million, while agriculture was found to be the most affected industry costing the UK economy around £1.1 billion.
The impact on construction, development and infrastructure was £270 million while tourism and recreation was £136 million, the scientists said.
Japanese knotweed, for example, has been known to cause structural damage to properties – which can be expensive to rectify – and decrease their values substantially.
Invasive rabbits can destroy agricultural areas by overgrazing, while their burrowing also impacts the quality of pastures.
Meanwhile H. fraxineus, which originated in Asia and is thought to have been brought to the UK on imported ash trees, incurs huge clean-up costs near roads, railways, buildings and other publicly accessible land.
Dr Richard Shaw, co-author of the research published in the journal Biological Invasions and Cabi senior regional director, of Europe and the Americas, said: “This assessment again shows the important costs of INNS to the UK economy.
“Few effects of INNS specific management efforts can be seen in these results.
“However, they highlight the need to continue prevention and early detection, followed by eradication of the highest-risk species prior to establishment.”
There are currently around 2,000 invasive alien species in the UK, with up to 12 new species establishing themselves every year.
It includes established species such as killer shrimp, giant hogweed, mink, and parakeets, as well as those that have arrived recently but have a high impact such as the sea squirt Didemnum vexillum and H. fraxineus.
Dr Rene Eschen, lead author and Cabi senior scientist covering ecosystems management, said: “Repeat assessments like this one are important to maintain a focus on the impact of INNS, changes in impacts as a result of new or spreading species, as well as the identification of potential impacts of management or policies.”
He said that while the overall cost of invasive non-native species to the economy has increased, there have also been decreases in some species, such as rabbits, possibly due to effective management.
The efforts of the UK’s Environment Agency also appear to have resulted in eradicating some existing infestations of water primrose, Dr Eschen added.
In February, the Government published its GB Invasive Non-native Species Strategy to provide a framework to minimise the risk of invasive species.
Defra head of GB Non-Native Secretariat, Niall Moore, said: “Invasive non-native species pose a serious threat to our natural environment and this Government is taking action through the recently launched GB Invasive Non-Native Species strategy, to protect our native animals and plants from INNS.”
He added: “It is vital that we work together with researchers, scientists and others, who are working to tackle INNS, to prevent their entry into and establishment in Great Britain and, when they do become established, to mitigate their negative impacts.”
