Invasive Alien Species

2 April 2014

Article by Katy Orford, National Assembly for Wales Research Service


Image from Flickr by USFWS-Pacific Region. Licensed under the Creative Commons.
Image from Flickr by USFWS-Pacific Region. Licensed under the Creative Commons.

In mid-2013 the Assembly’s Environment and Sustainability Committee undertook an inquiry into the impacts of IAS in Wales. The Assembly will be debating the Committee’s report on 2 April.

What are Invasive Alien Species (IAS)?

Non-native or ‘alien’ species are those that have been moved outside their natural range by human activity, either accidently or deliberately. If an introduced species subsequently survives and reproduces, then it is considered to have become established. Alien species are classified as invasive when their presence has negative consequences in the area where they are introduced, such as causing decline in native biodiversity, economic damage or impacting human health.

The rate of IAS establishment in Great Britain has steadily increased since 1800. A Defra commissioned study reported that in 2012 there were 280 IAS in GB, including fungi, microorganisms, plants and animals. Between 2000 and 2010, an average of 1.4 additional IAS established in Great Britain each year. It is predicted that the rate of IAS establishment will continue to rise, with growth in trade and travel and climatic change.

Which IAS are of particular concern in Wales?

Examples of IAS of particular concern in Wales include:

  • Rhododendron; out-competes native flora
  • Japanese knotweed; causes structural damage to infrastructure
  • Himalayan balsam; promotes river bank erosion
  • Slipper limpet; outcompetes commercially important shellfish
  • Signal crayfish; predates native fish eggs
  • Carpet sea squirt; fouls aquaculture equipment and mussel beds.

What is the cost of IAS in Wales?

The costs associated with IAS include the adverse impacts they cause and the cost of preventing, controlling or eradicating them. A Defra commissioned report by the Centre for Agricultural Bioscience International (CABI) in 2010 estimated market costs incurred by IAS to be £125 million per year in Wales.


IAS can also cause significant non-market costs by reducing native biodiversity and disrupting ecosystem service provision. A Centre for Agriculture and

Biosciences International (CABI) review of sixteen published assessments found estimates of non-market costs of IAS to be, on average, fifty-seven times higher than estimated market costs. This suggests the total cost of IAS could be as high as approximately £7 billion per year in Wales.


What action are the UK and Welsh Governments currently taking?

The GB Non-Native Species Programme Board was established in 2005 in response to Defra’s review of IAS policy which found a lack of coordinated efforts for IAS management in GB. The Programme Board comprises representatives from Defra, the Welsh Government, the Scottish Government and their relevant agencies and is supported by the Non-Native Species Secretariat (NNSS), which coordinates government and non-government stakeholder action. The Programme Board produced its Invasive Non-Native Species Framework Strategy for GB in 2008 which is not legally binding but lays out key recommendations for IAS management.

Implementation of this strategyin Wales is the responsibility of the Wales Working Group on Invasive Non-native Species which was established in 2008 and is chaired by the Welsh Government.

What is the relevant UK legislation?

The most notable legislation containing provisions relevant to IAS are Section 14 of the Wildlife and Countryside Act 1981, which controls the release and escapes of non-native species in GB, and the Natural Environment and Rural Communities Act 2006, which requires all actions undertaken by public bodies in England and Wales to have regard for biodiversity.

Is there any European legislation in place for managing IAS?

There is currently no single piece of legislation governing IAS management across the EU. However the EU institutions are in the process of negotiating a new Regulation that aims to do just this.

On 9 September 2013, the European Commission proposed legislation COM(2013)620 centred on control of 50 IAS of greatest EU concern, focusing on preventing introduction, early warning, rapid response and managing IAS that have already become established.

The European Council and the European Parliament have reached a provisional agreement on the new legislations. The Greek Presidency of the Council agreed to the Parliament’s recommendation that the list of IAS be open-ended and not capped at 50.

The agreement will have to be formally approved by the Parliament and Council of Ministers. The Parliament’s plenary vote is due to take place on 15 April 2014 and the Council is due to take its decision after the Parliament’s vote.

Further information:

European Commission Invasive Alien Species

GB Non-Native Species Secretariat

Research Service EU Policy Update Prevention and Management of the Introduction and Spread of Invasive Alien Species


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