The impact of Invasive Alien Species (IAS) can be manifold, ranging from loss of crops, damaged buildings, and additional production costs to the loss of livelihoods and ecosystem services. A number of estimates of the economic impact of IAS on various countries exist, but the detail in many of these estimates is lacking and the impact on different sectors of the economy is largely unknown.
This study estimated the annual cost of IAS to the British economy and provided assessments of the economic cost of IAS to twelve sectors. Case studies were also used to demonstrate the costs of control at different stages of invasion. The economic benefits of IAS were excluded, and the majority of costs are ‘direct use’ costs, not other non-use or non-market costs.
Costs were based on a detailed questionnaire followed up by detailed one-to-one interviews with individual experts and representatives of key organisations and combined with a thorough review of the scientific and grey literature and the internet which provided over 500 relevant references. The data were used to estimate the costs, partially based on calculations for individual species, which was anonymously reviewed by selected experts from each of the sectors.
The total annual cost of IAS to the GB economy was estimated at £1.7 billion. A meta-analysis of previous studies of the economic impact of IAS on the economy of various countries revealed that, on average, direct costs constitute only 1.75% of estimates of IAS costs. Therefore the estimated £69 million worth of costs caused by freshwater invasive species to the GB economy annually could be as high as £3.9 billion, though no work has been carried out to confirm or challenge this estimation.
Challenges included lack of IAS specific data, reluctance of people to share data and a lack of awareness of what species are invasive. This lack of data meant that extrapolations and assumptions had to be made, based on the ecology and biology of the species. Lack of time meant modelling methods could not be used.
More work is needed, with the purpose of the study guiding the methods used. Accurate modelling takes time and should be used when more precise data is needed. Estimates may be quicker and appropriate for a more general audience. If indirect and non-use costs are to be included a considerable amount of field research will be needed as these data do not exist. However, assessments of economic costs are one starting point in changing people’s attitudes to IAS and the damage they cause.