Invasive non-native species (INNS) are plants and animals introduced (either accidentally or deliberately) into a natural environment where they are not usually found with serious adverse consequences for the environment. INNS can give rise to physical damage to buildings and land, thus impacting on the value, marketability and insurability of the property in question. The cost of dealing with perhaps the most notorious INNS, Japanese knotweed, has risen to over £165 million per annum, with the government estimating that the cost of eradicating it entirely from the UK would be £2.6 billion. The presence of an INNS on a development site can lead to significant delays in development as the INNS in question is eradicated and treated. Furthermore INNS can impact on biodiversity as they can compete with native species and result in liability (both civil and criminal) for owners, occupiers and anyone handling the INNS if they fail to do so in accordance with the law. Ultimately the problems arising from the presence of an INNS can deter buyers, tenants and funders from proceeding with a transaction.
The most well known INNS in the UK is Japanese knotweed. This was introduced as an ornamental plant in the 19th century but is now the most invasive plant in the UK. It grows incredibly rapidly (up to 10cm in the spring and summer months) and has a vigorous root system which can penetrate foundations and walls causing extensive damage. Furthermore if even a small piece of root or stem is left in the ground it can quickly re-infest a site. In addition to Japanese knotweed there are number of other species that are subject to the same requirements for management and due diligence including giant hogweed and Himalayan balsam (both of which predominantly grow along watercourses), rhododendron and New Zealand pygmy weed and floating pennywort (which grow in freshwater).
The EU strategy
Published in 2011, the EU Biodiversity Strategy required the European Commission to develop legislation that specifically dealt with INNS. This resulted in the EU Invasive Alien Species Regulation 2014  which comes into force on 1 January 2015 (the Regulation). The Regulation aims to address the problem of INNS across the EU and requires that member states eradicate and manage certain specified INNS (which are referred to invasive alien species in the EU). The Regulation defines an invasive alien species as an alien species whose introduction or spread has been found to threaten or adversely impact on biodiversity and related ecosystem services (Article 3) and confirms that member states must draw up, and keep updated, a list of invasive alien species together with appropriate measures for their control and management (Articles 4-5) and prohibits the intentional introduction, keeping, sale or release of such species in the EU (Article 7). Member states are also required to take action to control unintentional introduction (Article 13), undertake early eradication and management of invasive alien species (Article 19) and introduce penalties for breach of the Regulation (Article 30).
Domestic strategy for control of INNS
Currently, the main legislation dealing with the control of INNS in Great Britain is the Wildlife and Countryside Act 1981 (WCA 1981). The WCA 1981 contains a list of certain plant and animal INNS that have established themselves in the wild but which the law seeks to prevent spreading further. Under the WCA 1981 a person would be guilty of an offence if they plant or otherwise cause to grow in the wild any plant that is included in Part II of Schedule 9 (similar offences can be committed in relation to the release or escape of a listed wild animal) . A person guilty of an offence is liable on summary conviction in the magistrates court for up to six months’ imprisonment, a fine not exceeding the statutory maximum (currently £5000) or both, or on conviction on indictment to two years’ imprisonment, a fine or both. It is a defence to prove that all reasonable steps were taken and all due diligence was exercised, provided that a defendant gives seven days’ notice to a prosecutor that he intends to rely on that defence .
It should also be noted that when plant INNS are disposed of as part of a removal process they may be classified as controlled waste and therefore subject to the requirements of the Environmental Protection Act 1990 (EPA 1990). Under the EPA 1990 depositing controlled waste in or on any land without a permit or in a manner likely to cause pollution is an offence as is breaching a duty of care by failing to take all reasonable steps to ensure that the waste is not disposed of in an unlawful way or in a manner that causes pollution or harm . Furthermore local authorities have powers under section 215 of the Town and Country Planning Act 1990 to serve notice on an occupier of land requiring it to remedy the condition of land where, in their opinion, the amenity of that area is adversely affected. Such powers could be exercised in relation to infestation by an INNS, especially where it is at risk of spreading into adjoining land.
Notwithstanding the existing laws which aim to deal with INNS, there has been a move towards amending wildlife law in England and Wales in recent years. In 2008, the INNS Framework Strategy for Great Britain was developed to tackle the issues posed by both plant and animal INNS and in 2011 the Law Commission commenced a review of the law on protection, management, use and welfare of wildlife and to make recommendations for its modernisation. As yet the Law Commission’s final report has not been published. At the request of DEFRA however the Law Commission has produced a separate report relating to the control of INNS entitled ‘Wildlife Law: Control of Invasive Non-Native Species’ which makes it clear that INNS pose a significant threat to both biodiversity and the economy and that the law as it stands does not contain sufficient powers to control and eradicate INNS in England and Wales. The report went on to suggest that a control procedure similar to that in Scotland should be introduced to permit the making of Species Control Orders (SCOs) to control INNS.
The Infrastructure Bill 2014-2015 (the Bill), which has passed through the House of Lords and is currently residing with the House of Commons, having had its first reading in November, amends the WCA 1981 to permit SCOs to be made in England and Wales in circumstances where voluntary agreements cannot be reached to control INNS. Clause 16 of the Bill would introduce a new Schedule 9A into the WCA 1981 which sets out a staged process for the making of an SCO which would commence with environmental authorities attempting to reach a voluntary agreement (a species control agreement (SCA)) with the landowner requiring them to control the INNS. For an SCA to be entered into the environmental authority would need to be satisfied that the content of the agreement is proportionate to the objective to be achieved and where there is more than one owner, that the owner with whom the SCA is entered into, is the most appropriate one. Where an SCA cannot be made and there is a significant threat from inaction the environmental authority would have powers to not only compel action on the part of the landowner by the making of an SCO but also to enter the land in question for surveillance or to carry out works to eradicate the INNS. Obstructing an environmental authority or failing to comply with an SCO would be a criminal offence punishable by imprisonment of not exceeding 51 weeks, a fine or both.
The Bill provides that in England, the Secretary of State, Natural England, the Environment Agency (the EA) and the Forestry Commissioners would be ‘environmental authorities’ entitled to make SCOs with the Welsh Ministers and Natural Resources Wales having the same powers in Wales.
Owners’ and occupiers’ liability and considerations for property transactions
Whilst the owner or occupier of land is not required to control, remove or treat INNS, failure to take reasonable measures to control one that results in the plant spreading into the wild or being negligent about it occurring could amount to the offence of causing it to grow in the wild under the WCA 1981. Therefore an owner or occupier of infested land would be well advised to take prompt action to control plant INNS. It is also worth considering that if a plant INNS spreads onto neighbouring land an owner or occupier could be liable for common law or statutory nuisance potentially entitling the neighbouring owner to compensation for loss of enjoyment and costs of removal and a continuing injunction against reinfestation. From a landowner’s perspective it is important to ensure that the correct remediation strategy is put in place dependant upon their plans for the site and an appropriate budget set aside to implement it.
The EA has issued specific guidance on managing knotweed on development sites  which provides guidance on prevention of spread, management plans, treating and disposal on site and dealing with the long term effects of knotweed. The guidance also summaries the relevant legislation and liabilities.
In terms of property transactions it is essential that adequate due diligence is carried out before committing to purchasing or leasing a site. A landowner is not under any duty to disclose information about the physical condition of a property and this extends to the presence of an INNS. Whilst it is possible that the commercial property standard enquires (CPSEs) cover INNS (enquiry 8.1 asks for details of infections or infestations on site and enquiry 15.7 requires details of environmental problems to be disclosed) a well advised buyer/tenant should raise supplemental enquiries relating specifically to INNS if they have any concerns. It is however, highly unlikely that a seller/ landlord will give a definite answer and will usually require a potential buyer/tenant to rely on its own inspection. In this case the buyer/tenant should commission a specific survey and inspection to ascertain whether there are any INNS’ on site and what the costs of a remediation strategy would be. A standard desktop environmental survey, as it is generally based on publicly available information and does not include a site visit, is not likely to reveal whether an INNS is present on site and as such a site visit by an environmental consultant or specialist knotweed consultant is essential. If knotweed (or another INNS) is present on site then specialist contractors will be required to undertake remediation. Ideally a guarantee for the work undertaken should be obtained with the guarantee backed by insurance so that the costs of retreatment would be covered even in the event of the insolvency of the original contractor. Such a guarantee should also be assignable to subsequent owners of the property to assist in its marketability. A buyer/tenant may also wish to take an indemnity from the seller/landlord to cover costs arising from potential proceedings as a result of the spread of the INNS to neighbouring land and the costs of compliance with notice to remove or manage the INNS.
A prospective tenant may also wish to give some consideration to the drafting of the repairing obligation in their lease in order that any liability for repair of damage caused by knotweed is excluded from the repairing obligation and the responsibility shifted on to the landlord by way of a specific covenant to repair such damage. The provisions relating to statutory compliance may need amending to remove any obligation to comply with statute so far as it relates to management of INNS. Service charge provisions may be amended to remove the costs of INNS management and, as mentioned above, an indemnity could be taken from the landlord in relation to costs incurred in dealing with knotweed.
It should be borne in mind though that no contractual or lease provision will protect a buyer/ tenant from criminal liability, for example under the WCA 1981.
It is clear that by strengthening existing legislation relating to INNS the Bill could have a significant impact on landowners. It is imperative that landowners and buyers/tenants of property have a clear understanding of the legislation relating to the control of INNS. Appropriate enquires should be raised when a site is being purchased however the responses to these enquiries may be insufficient to provide a buyer/tenant with the information they require to make an assessment as to the likely impact of any INNS on site. Sites where the presence of an INNS is suspected should be visited by an appropriately qualified surveyor in order that the likely financial impact of a remediation scheme can be ascertained. Finally, transaction documentation should be amended to ensure that, so far as possible, liability for any pre-existing INNS infestation is suitably apportioned.
 Regulation 1143/2014 of the European Parliament and of the Council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species.
 Sections 14(1) and 14(2) WCA 1981.
 Sections 14(3) and 14(4) WCA 1981.
 Sections 33 and 34 EPA 1990.
 Managing knotweed on development sites: the knotweed code of practice (version 3, 2013)