International Association
for Open Knowledge
on Invasive Alien Species
Horizon scan of invasive alien species for the island of Ireland

More harmful, environmentally damaging freshwater, marine and terrestrial invasive alien species are expected to arrive on the island of Ireland through human activity within the next decade. In recent months we have witnessed the global spread of the COVID 19 virus. Animals and plants from other countries can also be spread by humans in many different ways, both intentionally and accidentally. When invaders arrive and successfully establish in Ireland, many native species can suffer impacts and be displaced. Our native biodiversity is under pressure from invasive species that are already here, for example Japanese knotweed and zebra mussel, but studies indicate that with the increase in global transport and trade, many more are expected to arrive on our shores in the coming decade.

A Horizon Scanning workshop attended by 23 international experts has identified the top 40 invasive species most likely to arrive, establish and spread in Ireland in the next ten years. The event, hosted by IT Sligo, was part of an EPA funded research project on the ‘Prevention, Control and Eradication of Invasive Alien Species (2015-NC-MS-4)’ led by Professors Frances Lucy (IT Sligo), Joe Caffrey (INVAS Biosecurity Ltd) and Jaimie Dick (Queens University Belfast) with two PhD students Eithne Davis and Neil Coughlan. The Horizon scan has just been released as a peer reviewed publication and is also available in report form.

The top species in the horizon scan were selected on the basis of probability of arrival, establishment and biological impacts. The list of 40 included 18 freshwater invaders, 15 terrestrial and seven marine species. The North American signal crayfish (Pacifastacus leniusculus) was listed as the number one species considered most likely to invade Ireland and cause significant ecological impact. This particular species is the most widespread alien crayfish in Europe, is omnivorous, highly prolific, can live to 20 years and is adaptable to a wide range of environments. It also is a carrier of the crayfish plague, already a problem in Irish rivers and lake systems, and lethal for the Irish population of the protected white-clawed crayfish.

‘Management of invasive species is challenging, requiring adequate and sustainable financial and human resources. Prevention of introduction is by far the most practical approach. This Irish Horizon Scan has Identified the most likely invaders and their pathways of entry, enabling prevention management to be targeted in the most efficient and effective manner’, advised Prof Frances Lucy.

According to Prof Jaimie Dick, ‘This evidence-based list provides important information to the relevant statutory agencies in both jurisdictions in Ireland to prioritise the prevention of the most likely invaders and aid in compliance with legislation.’

Prof Joe Caffrey commented that ‘Targeted biosecurity in both jurisdictions is urgently required in order to manage the pathways of arrival, and is vital to maintaining native biodiversity on the island of Ireland.’


The paper is available as an open access publication in Management of Biological Invasions, a journal of the International Association for Open Knowledge on Invasive Alien Species (INVASIVESNET), and can be found here:  

For more information about INVASIVESNET, please visit our website - - or contact Prof Frances Lucy at


This project is funded under the EPA Research Programme 2014-2020. The EPA Research Programme is a Government of Ireland initiative funded by the Department of Communications, Climate Action and Environment. It is administered by the Environmental Protection Agency, which has the statutory function of co-ordinating and promoting environmental research.


Although every effort has been made to ensure the accuracy of the material contained in this Press Release, complete accuracy cannot be guaranteed. Neither the Environmental Protection Agency nor the authors accept any responsibility whatsoever for loss or damage occasioned or claimed to have been occasioned, in part or in full, as a consequence of any person acting or refraining from acting, as a result of a matter contained in this Press Release.


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