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Invasive non-native species within the UK

giant hogweed invasive non-native species

Invasive non-native species cost the British economy an estimated £1.7 billion annually. This is said to be a conservative figure and does not include indirect costs which could be substantially higher (Williams et al, 2010).  In the first of this series, Elizabeth Kimber (Ecologist), provides an overview…

An invasive non-native species is any non-native plant or animal that has the ability to spread, causing damage to the environment, the economy, our health and the way we live. Over the last 500 years nearly all invasive species have been introduced to new areas by humans.

Invasive non-native species are a problem within all countries worldwide because they can:

  • Replace a diverse system with a single species or impoverished eco-system;
  • Directly threaten native flora and fauna;
  • Alter the chemistry of the soil; and,
  • Alter geomorphological processes.
goose invasive non-native species

Canada geese (Branta canadensis) are considered to be an invasive non-native species

There are two methods used to control non-native invasive species – natural or chemical control.

Natural Control
Natural control comprises releasing another species to control the original invasive species; in some instances, this can cause further problems with the control species becoming invasive further down the line. The species used for natural control have to be investigated thoroughly by the Centre for Agriculture and Biosciences International (CABI) to check the control species will not have any adverse impacts on the area in which it will be released.

The advantages of natural control are that they are not genetically modified, they are safe as there will be stringent trials, the agent is species specific and natural control is usually more sustainable, economical and spreads naturally.

Chemical Control
Chemical control involves using a pesticide or herbicide to control the species, however this is usually more detrimental to the environment due to run off of the pesticide into local water systems etc.

fallopia-japonica japanese knotweed invasive non-native species

Japanese knotweed (Fallopia japonica)

The Law
The UK is bound by international agreements, law and policy such as:

  • Convention on Biological Diversity (Rio, 1992);
  • United Nations Convention on the Law of the Sea (1982);
  • Convention on the Conservation of Migratory Species of Wild Animals (Bonn, 1979);
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern, 1979);
  • EC Habitats and Species Directive (1992);
  • EC Water Framework Directive (2000) – The UK Technical Advisory Group (UKTAG) consider that non-native species are one of the significant pressures which could result in a waterbody failing to meet environmental objectives (such as failing to achieve good ecological status);
  • Sanitary and Phytosanitary Agreement of the World Trade Organisation (1995); and,
  • Schedule 9 of Wildlife and Countryside Act (1981).

All of these aim to protect biodiversity, endangered species and habitats.  They also include provisions, requiring measures to be implemented, preventing the introduction of, or control of, non-native species, especially those that threaten native or protected species.

In 2003 Defra commissioned a review of non-native species policy within the UK (excluding Ireland) and made eight key recommendations:

  • Form a lead, co-ordinating body;
  • Develop risk assessment procedures;
  • Develop codes of conduct for relevant sectors;
  • Develop an education and awareness strategy;
  • Revise and update existing legislation;
  • Establish a monitoring and surveillance programme;
  • Establish policies for the management and control of invasive species already present or newly arrived; and,
  • Engage stakeholders in developing policies and actions.
muntjac deer invasive non-native species

Muntjac deer (Muntiacus reevesi)

The Non-Native Species Programme Board has been formed to provide co-ordination at British level, consisting of representatives from relevant government bodies. A methodology has been developed to assess the risks posed by species that are already present and species that may arrive, in addition to routes of entry.  A consultation was held in 2007 concerning the draft Invasive Non-Native Species Strategy for GB, with the final strategy launched in 2008 and updated in 2015.

The strategy is based on the Convention on Biological Diversity’s three stage approach of prevention, detection/surveillance and control/eradication.

  • Prevention: this is the primary objective to avoid long-term costs. Consultations by Defra and the Scottish Government propose using a power introduced by the NERC Act and Nature Conservation (Scotland) Act to ban the sale of some of the most damaging invasive species; however, this could have economic consequences for retailers. Plantlife amongst others has suggested that the horticulture trade could aid prevention by correctly labelling stock and warning customers of the risks of releasing non-native species into the wild.
  • Detection/surveillance: The Non-Native Species Programme Board is reviewing options for a centralised information point on the internet for recording their presence in Britain. This portal would provide the country with an alert system and allow prioritisation of those species on which to complete risk assessments or develop actions. An app called Plant Tracker is available on phones which has been developed by the Environment Agency, Scottish Natural Heritage, Natural Resources Wales and the Scottish Environment Protection Agency to help combat the spread of the UK’s most problematic invasive, non-native plant species.
  • Control/eradication: most control/eradication programmes are localised and involve removing specific plants or animals from a particular waterbody or region. Large-scale control of plants or insects using co-evolved natural enemies is being examined. Eradicating invasive species before they become well-established saves time and money in the long-term.

Invasive plant species can be split into two categories, terrestrial and aquatic. Invasive aquatic species are often of greater concern than terrestrial ones as there is little surveillance in marine systems and limited control measures available for use in both freshwater and marine systems.

The main plant species of concern include Japanese Knotweed (Fallopia japonica), Himalayan balsam (Impatiens glandulifera), Cotoneaster sp. (Cotoneaster sp.), giant hogweed (Heracleum mantegazzianum) and a variety of waterweed species which are invasive.

Over the next few weeks I will be writing quick ID guides and treatment options for invasive species.

About the Author: Elizabeth Kimber works for an ecological consultancy based in Dorset (Lindsay Carrington Ecological Services Ltd).  As part of the role she manages the ecological works for a multi-phase development. She conducts protected species surveys and holds a class 1 bat licence, smooth snake and sand lizard licence. She can be contacted via email: liz (at)