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Contingency plan for invasive non-native freshwater plants

Last edited: 30 October 2023
Author: GB NNSS

PDF version


England, January 2020

1. Scope

This plan is designed to be used by government officials and sets out how government and agencies would respond to an incursion of any invasive non-native freshwater plant in England.  Similar plans are in place in Wales and Scotland.

This plan is generic, with species-specific information provided in separate annexes.  Annex 1 lists species on the horizon for which a response is expected as well as species for which there is a legal obligation to attempt a rapid response.

2. Legal position

Relevant legislation is set out on the ‘gov.uk’ website as well as the NNSS website (www.nonnativespecies.org).  Additional reference to species-specific legislation is included in the annexes of this document.  Defra are responsible for providing additional legal guidance and interpretation as necessary.

3. Policy, process and governance

Defra has overall policy responsibility for this contingency plan and officials will consult Ministers as necessary.  The Environment Agency has overall responsibility for its delivery.  A Response Group, led by the Environment Agency, will be responsible for overseeing the response, reporting to senior officials and Ministers, and escalation if necessary.  The Environment Agency will be responsible for implementation on the ground. Defra press office will be responsible for external communications, supported by the Response Group.  The following flow diagram illustrates the link between these organisations.  Annex 2 provides detail on the roles and responsibilities of each organisation and group.  Annex 3 provides a flow diagram summarising the roles and responsibilities during different stages of a response.

Flow diagram showing the links between organisations described in the text above. Ministers and senior officials are at the top of the diagram and instruct Defra. Defra instruct a response group including EA, Natural England, Defra, and NNSS. The response group instructs communications (Defra press office and response group) and the operations group (EA and agent/Natural England as required).

Stakeholder consultation and the role of volunteers

Stakeholder support will be important to a successful response in many cases.  Their role could include, but is not limited to: detection, assessment, access and communication.  Plans to engage stakeholders should be detailed in species-specific annexes of this plan.

4. Anticipation & Assessment

Risk analysis

The GB Programme Board for non-native species, chaired by Defra, is responsible for coordinating non-native species policy in GB (but note the Board is not responsible for non-native species related to plant or animal health).  The Board has established a GB risk analysis mechanism which provides evidence of the risk posed by non-native species as well as the feasibility of management.  The process is managed by the Non-native Species Secretariat, with a dedicated panel of risk analysis experts (known as the Non-native Risk Analysis Panel) responsible for ensuring risk assessments are fit-for-purpose.  The Board has also established the Non-native Species Information Portal which has responsibility for horizon scanning, which is undertaken at regular intervals.

Ideally risk assessments (rapid or detailed) and risk management appraisals should be completed before species invade.  However, where this is not the case it should not prevent a response.  Instead a rapid assessment should be completed as soon as possible following invasion.

Where available a summary of the risk assessment and risk management appraisal should be provided in the species-specific annex.

Specific contingency plans

This generic plan, supported by species-specific information provided in its annexes, should be sufficient for most freshwater plant responses.  However, where there is need, separate species-specific contingency plans should be developed.

5. Preparation

Staff resources

The EA, or an agent working on its behalf, will provide the initial emergency response capability.

If necessary the EA will seek authority to require the release of further staff from Defra and Defra Agencies to work on emergency duties.

Defra has arrangements in place which identify suitable volunteers who could provide assistance to an emergency for core Defra policy roles. The Emergency Response Group has volunteers from across the Department who would support Defra emergency teams in the event of a serious and sustained outbreak.

If necessary, Defra will also trigger the use of the cross Government Memorandum of Understanding on Mutual Aid and the Redeployment of Human Resources. This relates to the loan of staff from other government departments.


Response and Operational staff should be familiar with this plan and trained in its delivery.  Where necessary, short exercises should be undertaken annually to test preparedness for an outbreak event.

Operational staff should be familiar with relevant management techniques and obtain relevant training where necessary. 


The EA will be responsible for ensuring suitable equipment is available to deliver responses to the species identified in Annex 1.  This could include maintaining a stock of equipment, or ensuring there is a ready supply of stock to be brought in as necessary.

The EA will be responsible for sourcing additional equipment as necessary for an invasion of any species not listed in Annex 1.

Evaluation and review

A review should be carried out after all outbreaks, and as necessary following exercises, to identify lessons learned and improve future responses.  Reviews will be led by the EA and centrally stored by the NNSS.

6. Detection

There is no dedicated surveillance for invasive non-native freshwater plants in Britain.  However, freshwater non-native species may be recorded during other surveys by government bodies (e.g. EA, EA, CEH, etc.).

The Botanical Society for the British Isles (and other non-governmental organisations) monitors plant distributions in Britain and is likely to detect and record freshwater non-native plants.

Reports are also made by the general public.  This is encouraged through the provision of identification information and an alert system (alertnonnative@ceh.ac.uk). 

7. Response

A response is triggered when:

  • A species listed in Annex 1 of this document is reported in the wild in England.
  • Any other freshwater plant is reported in the wild and identified as a significant threat by Defra, in consultation with its advisors.

In most cases it should be feasible and cost effective to eradicate a new population of an invasive non-native freshwater plant. 

Populations discovered in private ponds or commercial facilities may require a different response.  This will be at the Response Group’s discretion (see below).

Official action on suspicion       

Reports of individual freshwater plants may not necessarily require a response.  The Environment Agency will determine when a sighting should be considered of concern, in consultation with Defra and NNSS.  A report is likely to be a concern if there is evidence to suggest a self-sustaining population has formed (i.e. present over multiple years, indications of spread).

In the case of species listed at Annex 1, a response is required should any self-sustaining population be detected or suspected.  For species not listed at Annex 1 the Environment Agency will determine whether a response is required, in consultation with Defra and NNSS.

Difficulties in resolving the identity of a specimen will be resolved by the Environment Agency, with support of other organisations and experts (e.g. Botanical Society for British Isles, Natural History Museum, etc. as required).

Official action on confirmation

The Environment Agency will confirm that a population of concern has been detected that may require a response.  On confirmation, the EA will establish the Response Group (responsibilities of all groups are set out in Annex 2) which will provide recommendations for action.  To help inform their decision the Response Group may undertake (or commission) a risk management appraisal.  The Environment Agency, or an agent working on its behalf (termed here the Operations Group for consistency), will carry out the eradication.  Senior officials and Ministers will be kept informed as necessary.

In delivering the eradication, the Operations Group will:

  • Undertake monitoring / surveillance as necessary.
  • Liaise with landowners and interested parties as necessary to obtain access and other permissions, if necessary utilising species control orders.
  • Determine and implement the eradication strategy.
  • Investigate the source of the outbreak and pursue any appropriate legal action.

Escalation and standing down

If for any reason eradication is more difficult than expected or not considered feasible, the Response Group will advise senior officials / Ministers of the need for escalation of eradication efforts or to stand down and move to long term management.

In the case that eradication effort is stood down, management responsibility would usually revert to those that are affected by the invasive non-native species (e.g. local landowners, local authorities, farmers, householders as well as government bodies where interests are threatened such as on sites designated for conservation interest, etc.).  The Response Group would usually be responsible for providing management advice to affected parties.

8. Resources and costs of response

Eradication of newly detected invasive non-native plants is expected to cost in the low £10ks.  However, this may rise if the population is very large, multiple or difficult to access or in sensitive habitat.

9. Risks to a successful response

Herbicides are often required to eradicate freshwater plants.  Increasing regulation is reducing the number of herbicides available for use, which may pose a risk to effective management in some cases.

Lack of cooperation from landowners is a potential risk.  Liaison will be carried out by The Environment Agency in the first instance to reduce this risk, with support from the Response Group where necessary.  Where negotiation is unsuccessful Species Control Agreements / Orders will be used to enforce access.  It is not envisaged that there will be difficulties accessing publicly owned land; however relevant bodies, such as the Forestry Commission, should be consulted at an early stage.

10. External communications

Press lines

Defra press office will be responsible for external communications, with support from the Response Group.  Reactive lines should be prepared for each species on suspicion, confirmation, during a response, following a response and in the case of a need to escalate or stand down.  Proactive messaging should be considered where possible and appropriate.  External communications should take into account local and national stakeholders and should be developed and shared with them where appropriate.

Communication with external stakeholders

The Response Group is responsible for communicating with national stakeholders as appropriate.  A list of potential stakeholders with an interest in freshwater plant responses is provided in Annex 4.

ANNEX 1: Species to which this plan applies

This plan applies to invasive non-native freshwater plants that Defra has identified in advance of an invasion (Table 1).  It should also be used to respond to any new invasive non-native freshwater plant not listed, at the direction of Defra and ideally on the basis of rapid risk analysis.

Certain species are listed because the UK has a statutory obligation to eradicate under EU law.  The reason for listing each species is given in the table below.

Table 1. List of invasive non-native freshwater plants identified for rapid response in advance of an invasion

Scientific name

English name

EU Reg Species[1]

Horizon scanning[2]

UK Risk

Feasibility of eradication[3]

Alternanthera philoxeroides

Alligator weed



Not assessed

Not assessed

Eichhornia crassipes

Water hyacinth



Not considered able to establish in UK

Gymnocoronis spilanthoides

Senegal tea plant



Not assessed (low)

Not assessed

Ludwigia peploides

Floating primrose willow




Not assessed (high)

Myriophyllum heterophyllum

American watermilfoil




Very low

[1] Listed as species of Union Concern under EU IAS Regulation

[2] Identified as within the top 30 threats from invasive species not yet established in GB

[3] Based on most likely scenario of invasion

ANNEX 2: Roles and responsibilities

Defra will:

  • Provide updates to the Press Office and agree media handling plans.
  • Apply for any necessary and additional funding required for the duration of the outbreak.
  • Inform the EU Commission and other member states as necessary.

The Environment Agency will:

  • Establish and chair the Response Group.
  • Establish a framework for the overall management of the outbreak.
  • Provide resources and set limitations on resources.
  • Ensure clear lines of communication.
  • Commission advice from scientific advisors and/or core stakeholders if required to facilitate decision on strategic direction.
  • Undertake appropriate liaison with other agencies and stakeholders.
  • Develop, communicate and monitor the plan.
  • Provide technical advice as required.
  • Ensure staff have the required training and equipment.

The Response Group (led by the EA, with Defra, NNSS) will control the response and:

  • Update Defra Ministers, senior officials, and Devolved Administrations about the outbreak.
  • Develop recommendations as necessary for Ministers on control policies based on scientific advice.
  • Agree communication and stakeholder engagement plans.
  • Commission additional analytical work if there is insufficient understanding of the outbreak and/or its spread.

Operationally, the Environment Agency will implement the response and:

  • Assess the extent of the outbreak, the number of required resources and risks.
  • Liaise with stakeholders and land owners on the ground as necessary.
  • Provide overall management of field activities.
  • Provide regular updates to the Response Group.

ANNEX 3. Diagram of example stages in a response and responsibilities

ANNEX 4. Non-exhaustive list of potentially relevant national stakeholders

  • Angling Trust
  • Association of Rivers Trust
  • Botanical Society of Britain & Ireland
  • British Canoeing
  • Canal and Rivers Trust
  • Freshwater Biological Association
  • Freshwater Habitats Trust
  • National Trust
  • Ornamental Aquatic Trade Association
  • Plantlife
  • Royal Horticultural Society
  • Royal Yachting Association
  • The Wildlife Trusts
  • Water companies
  • Wildfowl and Wetlands Trust
  • Wildlife and Countryside Link

ANNEX 5. Template for species-specific information requirements

Box – issues to be resolved in advance of an invasion

  1. Policy and governance
    • State the policy aim.
    • If necessary, clarify any roles above and beyond that given in the generic plan.
  2. Legal position
    • Species-specific law that is relevant
  3. Risk assessment
    • Is a risk assessment available – summarise it.
  4. Risk management
    • Is a risk management appraisal available – summarise it.
  5. Detection
  6. Training and equipment
    1. Training requirements
    2. Equipment requirements
  7. Response
    1. Official action on suspicion [cover trigger points]
    2. Official action on confirmation [cover surveillance requirements, scenarios and eradication methods]
    3. Post eradication monitoring requirements
    4. Escalation and standing down thresholds and responses
  8. Resources and costs
  9. Specific risks to successful response (beyond those stated)
  10. External communications
    1. Press lines (on suspected sighting, confirmed sighting, during eradication, following removal, in the case of standing down).
    2. Communication with external stakeholders
  11. Role of stakeholders
  12. Supporting information

ANNEX 6. Species-specific contingency information

To be added as required.