Invasive species, like the grey squirrel, European rabbit and Japanese knotweed, have cost the UK economy over £5 billion over the past 40-50 years, according to researchers. The impact on agricultural production and damage to property were among the biggest contributors to the staggering figure. Invasive species are defined as those introduced and spreading outside of their native range as a result of human activities.

The report led by Queen’s University Belfast explains that invasive species are a growing threat to environments worldwide and one of the main causes of biodiversity loss.

While the issue's environmental impacts have been well studied, few reports examine its economic impact. This Queen's study published today (Thursday, July 29) in the journal NeoBiota is the largest and most up-to-date combination of economic costs of biological invasions in the UK. Researchers hope the new study will raise awareness of the huge economic burden that invasive species have on the UK economy and will promote greater management spending to prevent their damage.

'Costs are severely underestimated'

The study was first-authored by Dr. Ross Cuthbert, research associate from the School of Biological Sciences at Queen’s University and postdoctoral research fellow from GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany. It involved an international team of researchers that have built the first global database of invasion costs named InvaCost, led by a team at Paris-Saclay University.
Image source QUB
Red swamp crayfish. Photo: Clothilde Pérot-Guillaume
Dr. Cuthbert said: “We have found the majority of costs were caused by direct damages, such as reductions in agricultural productivity and infrastructure repair costs, whereas very little was spent on the actual management of invasive species, and especially the prevention of future invasions. “Worryingly, we also found that invasion costs are increasing rapidly over time and are likely to continue rising in future as more invasive species arrive in the UK.
These costs are also severely underestimated, as very few of the known invasive species in the UK have reported economic costs (less than 10%), indicating a lack of research effort and reporting of their detrimental impacts.”

Where do the costs come from?

To conduct their study, the researchers examined how costs in the UK were distributed across different invasive species, environments and cost types, and how they have changed through time.

They found that in the last 40-50 years, invasive species have cost the UK economy over £5 billion, with most of the cost due to invasive animals and plants, such as the European rabbit, Japanese knotweed and waterweeds, and predominantly through agricultural or property impacts.

For example, invasive rabbits cause severe damage to agricultural areas by overgrazing, which affects both the growth and yield of key crops, especially considering grasslands and cereals. Their burrowing can also impact the quality of pastures. Japanese knotweed causes structural damage to property that is expensive to remediate and reduces house values substantially. Invasive waterweeds can clog waterways, blocking access by watercraft, worsening flood risk and impeding recreational activities such as angling. Dr. Cuthbert added: “Investing in better biosecurity to prevent invasive species from arriving in the first place could reduce future economic impacts and be much cheaper than future damages or long-term control.” The research was funded by the French National Research Agency, the Alexander von Humboldt Foundation, AXA Research Fund, and the BNP-Paribas Foundation Climate Initiative.
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