Invasive alien species are species that have been introduced, either deliberately or unintentionally, to areas that are typically outside of their natural range or habitat. Over the last century increasing travel and trade have allowed many species to overcome the geographical barriers that previously restricted them. A number of these are highly invasive, establishing themselves in new terrestrial and aquatic environments.
These web pages provide an introduction to the most invasive of the alien species that are currently found in Northern Ireland. Some of those that may become established in the near future are also included.
After habitat destruction invasive alien species are the biggest threat to native biodiversity.
Invasive alien species can have a significant impact on ecosystems, native species, economic interests, e.g. agriculture and fisheries, and even public, plant and animal health. Negative impacts include: competing with native species for food and shelter, feeding on native species, and interbreeding with native species thus reducing their genetic purity. Some alien species carry disease which can infect and kill native species.
Northern Ireland has been subject to the impacts of many invasive alien species. Within a relatively short time-scale we have already witnessed the establishment of species which are currently having a detrimental effect upon our local biodiversity. There is therefore a rising and ongoing need to address the impact of invasive alien species.
Some species have already become established throughout Northern Ireland (for example, New Zealand flatworm), but there are also species which are likely to do so within the coming years (for example, Harlequin ladybird).
The need to address the issue of invasive alien species is recognised in the Convention on Biological Diversity, to which both the UK and Irish Governments are signatories. In Recommendations to Government for a Biodiversity Strategy 2002, the Northern Ireland Biodiversity Group (NIBG) identified "an urgent requirement to review the status of introduced species, ideally at an all-Ireland level". The Irish Government also identified a similar need in its National Biodiversity Plan for Ireland 2002.
In response to the NIBG recommendation, Environment and Heritage Service (EHS) Northern Ireland and National Parks and Wildlife Service (NPWS) in the Republic of Ireland commissioned a report on Invasive Species. A series of recommendations have been made, which include control and management of established invasive species and responding to new invasions. Implementation of these recommendations is due to begin in 2006.
The Wildlife (Northern Ireland) Order 1985 makes it an offence to deliberately introduce invasive alien species.
There is a role for individuals, special interest groups and landowners through for example, recording of invasive alien species or practical control. The individual species pages suggest action that can be taken and organisations to contact.
Text written by Biodiversity Unit, Northern Ireland Environment Agency.