Invasive Species

What are Invasive Alien Species and why are they a problem?

Grey squirrel
Kkev Chapman, flickr, cc-by-2-0


Invasive Alien Species are plants and animals that have been introduced to a new area outside of their normal range, where in the absence of natural controls such as predators or disease, they spread rapidly and cause ecological, health and or economic impacts in their new environment.

Most introduced species do not cause harm in their new environment, however a small number do become naturalised and a few of these become invasive and a serious pest. Invasive species are considered to be the second greatest threat to biodiversity worldwide after habitat loss.

Invasive species cause a range of environmental problems such as:

  • Out-competing native species for resources such as space or food.
  • Introducing new diseases and parasites affecting native wild or domestic species.
  • Diluting of native gene pool by interbreeding with native species
  • Predation of native species or grazing of native plants/habitats.
  • Erosion, alteration of waterways, flooding and visual landscape impacts.

The economic impacts of invasive species can be very high from both direct impacts such as loss of earnings due to invasive species or from the cost of managing or eradicating invasive plants or animals. A 2013 study estimated the cost the annual cost of invasive species to the Irish economy at €202,894,406 while the cost to the economy in the UK was estimated at €2.3 billion (Kelly et al, 2013).


The key legislation dealing with problem Invasive Species in Ireland is the European Communities (Birds and Natural Habitats) Regulations, 2011 (S.I. No. 477 of 2011).

Under Section 49 of the regulations, it is an offence to: plant, disperse, allow or cause to disperse, spread or cause to grow any plants or animals not ordinarily resident in the state as well as those listed in Part 1 of the Third Schedule.

Section 50 of the Regulations makes it an offence to: import, buy, sell, breed, reproduce or propagate, advertise, offer or expose for sale, publish a price list, transport or distribute; any animal or plant species or vector material listed in the Third Schedule. Regulation 50 is not in effect until the date on which the Minister gives public notice of this.

In certain circumstances, a licence may be obtained to permit these activities.

Thirty five plant species and approximately 41 animal species are listed in the Third Schedule (Appendix). Two vector materials are listed:  1. blue mussel seed and 2. Soil or spoil taken from places infested with Japanese knotweed, Giant knotweed, or their hybrid Bohemian knotweed.

The EC Regulation on the prevention and management of the introduction and spread of invasive alien species [2013/0307 (COD)] came into force for member states in January 2015.  It has a number of measures to counter the threat of invasive species within the territory of the European Union. This includes restrictions on the introduction, keeping, breeding, trading or transportation of species on the list of invasive alien species of Union concern. Member States will be required to put monitoring and control strategies in place to deal with listed species. There are 37 species on the ‘Union list’, of which 9 are already found in Ireland including the Grey squirrel, Muntjac deer, Chinese mitten crab, Red-eared terrapin/slider, Ruddy duck, Curly waterweed, American skunk cabbage, Floating pennywort (Northern Ireland) and Parrot’s feather

This page was added on 01/11/2016.

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