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The term 'non-native species' is the equivalent of 'alien species' as used by the Convention on Biological Diversity. It refers to a species, subspecies or lower taxon, introduced (i.e. by human action) outside its natural past or present distribution; includes any part, e.g. seeds, vegetative growth of such species that might survive and subsequently reproduce.

There are many non-native species in UK, but only a small proportion are invasive. An invasive non-native species is any non-native animal or plant that has the ability to spread causing damage to the environment, the economy, our health and the way we live. For the purposes of this guidance sheet, these species will be known as invasive species.

The problems caused by invasive species affect us all, costing in the region of £1.7 billion every single year in the UK. Their impact is now so significant that they are considered to be one of the greatest threats to biodiversity worldwide, even more than pollution or climate change.

It’s not just our wildlife that suffers, invasive species can also have an impact on the way we live. Some species have a direct impact on our health (Giant Hogweed) while others have less apparent, but just as serious effects such as flooding.

A number of riverside and aquatic invasive plants are widely considered to increase the risk of flooding. They do this by clogging water courses with plant material or sometimes in the case of Himalayan Balsam and Japanese knotweed by causing riverbank erosion which can lead to sediment getting into the watercourse. Sediment run-off also has negative implications on fisheries and the overall ecology of rivers.

Once a species has been introduced the problems persist and escalate as the species spreads further, causing us to feel more of the impacts and incur more cost every year. In urban environments, invasive species can be aesthetically detrimental and make places to live less appealing. Ponds clogged with invasive water plants can reduce their appeal and some species, such as Japanese knotweed, can encourage deterioration in the built environment, encouraging vermin and providing opportunities for littering.


Under the Wildlife and Countryside Act 1981, Schedule 9, Section 14 (as amended) it is an offence to deliberately cause (Invasive Species listed under Part II of Schedule 9 Wildlife and Countryside Act (WAC) 1981) to grow in the wild.

Invasive Species listed under Part II of Schedule 9 WAC Act 1981 are also subject to Section 34 of Environmental Protection Act (1990) and are classed as ‘Controlled Waste’. Consequently they should be disposed of at a licensed landfill site under the EPA (Duty of Care) Regulations (1991).

Invasive plant material is considered a ‘controlled waste’ and must be disposed of in accordance with, an environmental permit issued under, the Environmental Permitting (England and Wales) Regulations 2007, unless one of the exemptions set out in Schedule 3 of these regulations applies, although exemptions also require registration with the Environment Agency. Managing invasive non-native plants in or near fresh water.

NB. Removal and disposal of invasive species can only be undertaken by a licensed carrier. There are currently no disposal sites in Bridgend County Borough.


The maximum penalty for non-compliance with Section 14 of the WCA 1981 for each offence in the Magistrates’ Court is a £5000 fine and/or six months imprisonment and an unlimited fine (subject to the discretion of the court) and/or two years imprisonment in the Crown Court. If these species are not disposed of in the correct manner, a civil offence would occur and can be prosecuted by Natural Resources Wales. Infringement of the Environmental Protection Act can result in an unlimited fine.

Encountering invasive plant species

Guidance Note 1: Where invasive plants occur on development sites, an invasive species management plan which includes full details of a scheme for its eradication and/or control is to be submitted and approved by the council prior to the commencement of work on site and the approved scheme shall be implemented prior to commencement of work on site.

The above scheduled plant species require specific control and removal methods, due to their ability to affect both wildlife and human health.

These species, if they are found to occur on or adjacent to your site during the ecology survey, should be highlighted on a constraints plan. Measures should be put into place to arrange their removal and disposal in consultation with an appropriately qualified ecologist and contractor and subject to compliance with the above legislation.

Many development sites experience invasive species colonisation. The most frequently encountered invasive plants in Bridgend County Borough developments in urban areas are Japanese Knotweed and Himalayan balsam. It is essential that invasive plant species if present on or adjacent to the site are identified before works begin.

The invasive species management plan be put in place for all scales of development. This plan will help developers identify the areas where the plants occur on and adjacent to the site and the level of contamination.

Invasive species management plans should include a Method Statement ensuring that everyone working on the site is aware of and adheres to good site hygiene. This can be done by marking out contaminated areas, ensure that vehicles with caterpillar tracks do not work within contaminated areas where possible, treat contaminated soils carefully ensure that machinery or equipment that could be contaminated is cleaned.

An invasive species management plan will help developers deal with the implications of invasive species and will identify good working practices to provide an efficient cost effective solution. A management plan will also set out the procedures for taking potentially contaminated soil off site under the provisions of Section 34 of the Environmental Protection Act 1990 and EPA Regs 1991. Section 34 of Environmental Protection Act (1990) and the EPA (Duty of Care) Regulations (1991).

Home owners to large scale developers can produce invasive species management plans by understanding the implications of finding invasive plants on site.

Implications of invasive plants on or adjacent to the development site

The independent report Economic cost of Invasive nonnative species on Great Britain (2010) xcix estimated the total annual costs of Invasive Non Native Species to Wales as £125,118,000.

There are no definitive industry wide figures for how much the plant costs, but even on relatively small sites the cost of control can run into hundreds of thousands of pounds and the annual cost across the UK is likely to be many tens of millions. The cost to eradicate Japanese Knotweed in Britain using conventional methods has been estimated at £1.56 billion.


There are several options for the control and eradication of invasive plant species. Advice regarding the use of appropriate options is dependent on several factors including:

  • The development timescale;
  • The presence of nearby water bodies/land drainage;
  • Landscaping requirements;
  • Other protected species issues.

Prior to treatment

The first stage would be to identify all of the locations of the invasive species on and adjacent to the site and effectively safeguard their locations. If possible the locations could be plotted by GPS but it is also recommended to fence off the location(s).


Vigilance can be encouraged by the provision and display of identification information where contractors working on site have ease of access. The Environment Agency species secretariat provided a suite of identification sheets

The treatment of the commoner invasive species on development sites such as Japanese knotweed, Himalayan Balsam can be straight forward, but will involve repeat treatments to ensure eradication. However, in the instance of giant hogweed, this species has additional health and safety implications that must be taken into consideration.

Given that the above invasive species are more likely to be encountered on development sites within the Bridgend county borough area, the following sets out management approaches generally aimed at these species.

Herbicide Treatment

NB. Developers should seek advice of a suitably qualified pesticide operator or BASIS registered pesticides advisor before starting a herbicide treatment programme.

Treatment of Japanese knotweedinfestations can usually require a 3 year treatment programme with spraying being undertaken at the end of the growing season normally August/September) to effectively eradicate the plants. Annual monitoring visits should be conducted during April/May for 3 years following the initial 3 years of spraying. Should any regrowth be identified the annual spraying regime should be implemented.

Treatment of Himalayan balsam should be undertaken before the plant set seeds and when the plant has put on sufficient growth to ingest the herbicide sufficiently. This normally occurs around May and early June, depending upon the growing season. Himalayan balsam has a viable seed bank for about of approximately 2 years. Therefore, a spraying programme of 3 years should be considered. Annual monitoring visits should be conducted during April/May for 3 years following the initial 3 years of spraying. Should any regrowth be identified the annual spraying regime should be implemented.

However, strimming and in the instance of smaller infestations hand pulling, before the balsam flowers, is the most effective means of managing Himalayan balsam.

Treatment of giant hogweed is likely to be required for at least 5 years with monitoring continuing for a further 5 years. A detailed schedule of works for the annual treatment and monitoring programme is required. Annual monitoring visits should be conducted during April/May for 5 years following the initial 5 years of spraying. Should any regrowth be identified the annual spraying regime should be implemented.

It will be a requirement of the invasive species management plan to include precautionary measures to avoid drift spraying that may affect a site’s native flora/fauna.

Annual monitoring followed by spraying upon identification of new growth should continue until no regrowth is identified. An ecologist should inspect the re-growth during the following growing season and instruct Landscape Contractors to carry out the recommended follow-up work.

An appropriate herbicide should be selected in consultation with Natural Resources Wales, and the applicant’s appointed ecologist if wildlife constraints exist on

Should the stands of invasive species be positioned close to watercourses or water bodies then only those herbicides authorised by the Natural Resources Wales for use on knotweed on/near water shall be used, the competent contractor should know what is appropriate. 


Excavation is an option for immediate removal of invasive species subject to Section 34 of Environmental Protection Act (1990) and the EPA (Duty of Care) Regulations (1991). This method is recommended suitable for those stands that are to be directly affected by the sites remediation works.

It is recommended that invasive species that are to be affected by remediation works are sprayed, using an appropriate herbicide, followed by the removal of the weakened plants by excavation. Stockpiling or burial of the contaminated material is recommended following excavation.

The excavated plant material, must be carried out using appropriate methods to minimise the risk of further infestations occurring within the site.

In the instance of Japanese knotweed, this plant’s prime means of colonisation is through the spread of its underground stem system, known as rhiziomes. These rhizomes can extend to a depth of 3m and 7m laterally from the above ground stems. The entire root system must be removed to ensure no re-growth occurs.

Both Himalayan balsam and giant hogweed spread by spread by seed. Therefore, soil should be removed laterally and to a depth agreed with the developer’s ecologist and Natural Resources Wales.

Following excavation, the area must be regularly monitored in order to identify any regrowth. Should regrowth be identified a spraying regime should then be implemented.

Vehicles used to excavate the contaminated material need to be washed in order to prevent spreading these plant species. Any water used for cleaning these vehicles should be collected. If the water is contaminated with seeds or plant material, it will not be possible to discharge it into a watercourse. Contaminated water should be passed through a settlement tank to remove any soil before passing it through a very fine mesh sieve to remove seeds or plant material.

Material sieved from water used for vehicle washing may be deposited in a controlled area of the site and monitored for regrowth.

Two options following excavation are available; the material can be removed off-site to a licenced site and subject to the Section 34 of Environmental Protection Act (1990) and the EPA (Duty of Care) Regulations (1991) or retained within the site in a prepared receptor area to be stockpiled or buried.

If the invasive plant material is to be retained on site, there are two options for its disposal.

Stockpiling or bund method

If the site has areas invasive plant material can be left for at least three years then stockpiling is an option. Following excavation, the material would be transported to and stockpiled on the prepared area to enable the herbicide treatment to continue.

Bunds can be raised or an excavation made to contain the stockpile. In either case the enclosed area needs to be large enough to hold the volume of excavated contaminated soil and be lined with a root barrier membrane to protect the surrounding soil from unintentional cross-contamination.

Within any bunded or excavated stockpile it is the aim to concentrate the plant material in a thin upper surface of soil of no greater than 1m in depth. This will enable the plant to grow readily from in order to receive the continuing herbicide treatment later.

It is also recommended that the bund or stockpiled material should receive some disturbance through being turned over after 1 or 2 herbicide treatments. The disturbance will stimulate re-growth. The re-growth can then be chemically treated with the appropriate herbicide.

NB. This method of treatment is not usually suitable for giant hogweed and Himalayan balsam, due to the large number of seeds that may be dispersed by the wind. However if treatment occurs before regrowth is allowed to set seed, this method may be suitable.

Cell formation or burial method

NB: Burial on-site may require a licence under the Landfill Regulations 2002. The developer is advised to enquire whether they are required to obtain a licence before works commence.

If agreement with the environmental regulator can be met, invasive plant material can be excavated and buried on site within a lined cell or in a deeper excavation on site.

The first method involves creating a cell, lined with a root-barrier material, set below ground level. The contaminated material is then deposited within the cell which then needs to be adequately sealed with the root-barrier liner and covered with at least 2m depth of spoil and/or soil.

A burial method can also be carried out without using a root-barrier membrane. However, in this case the site must be able to provide an area where burial can take place below a depth of at least 5m from the finished surface. It is recommended that the material containing Japanese knotweed, Himalayan balsam and giant hogweed are chemically treated prior to the burial with a non-persistent herbicide.

It is important to notify the local Natural Resources team prior to the burial. An inspection of the material to be buried and the burial location may be required.

It is also necessary to accurately map and record the location of the burial site so that details can be kept with title deeds to inform subsequent owners of its position. This will help to prevent the accidental damage and subsequent reinfestation of the site through any future works.

Inspections of the area containing the buried material must be conducted yearly for at least 3 years to ensure no new growth has occurred through inadvertent contamination of the surface material.

Landscaping Schemes

Landscape schemes must ensure that species listed in Schedule 9 are not included within the design.

For further advice on preferred species in relation to landscaping schemes, see the emerging BCB Landscape and Local Character Design Guidelines.

Brownfield sites and Invasive Species

The development of land in particular brownfield sites can often have problems associated with previous activities. The land is often contaminated, and requires decontamination before development can proceed. Integrating new development into the existing urban development has control issues. For example, Policy ENV7 Natural Resource Protection and Public Health Development; only permit proposals where it can be demonstrated that they would not cause a new, or exacerbate an existing, unacceptable risk of harm to health, biodiversity and/or local amenity.

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