Invasive species Contents


1.Invasive non-native species (INNS) are one of the top five threats to biodiversity worldwide.1 On average INNS cost the UK economy £1.8 billion per year, mainly affecting agriculture, forestry, horticulture, utilities, construction and transport infrastructure.2

2.In April 2019, we launched our inquiry to examine the Government’s progress since our predecessor Committee’s 2014 report: Invasive Non Native Species.3 As part of our inquiry we held a useful evidence session at St Catharine’s College, Cambridge on biosecurity and the Overseas Territories and had an insightful discussion with the Cambridge Conservation Initiative. We also visited the Walthamstow Wetlands to learn from Thames Water about its approach to tackling invasive species. We received 125 written responses and held four public evidence sessions, hearing from 27 witnesses including academics, non-governmental organisations, trade associations and Government agencies. During Invasive species week (Monday 13 - Friday 17 May) we opened an online discussion forum for members of the public to contribute their views, which received 655 submissions. Finally, we heard from Lord Gardiner, Parliamentary Under Secretary of State for Rural Affairs and Biosecurity, Professor Nicola Spence, Chief Plant Health Officer and Dr Niall Moore, Chief Non-Native Species Officer at DEFRA. We are grateful to all those who hosted us and participated in the inquiry.

Defining invasive species

3.An invasive species is “any non-native animal or plant that has the ability to spread, causing damage to the environment, our economy, human health and the way we live”.4 Non-native species are those living outside their natural range which have arrived by human activity, either deliberately or accidentally. Of these, invasive species are those that negatively affect native biodiversity, ecosystem services and public health, through predation, competition or by transmitting disease. Professor Helen Roy, from the Centre of Ecology and Hydrology (CEH) told us, “when we think of all of the non-native species, it is very important to remember that about 15 per cent are the troublesome ones”.5

4.Witnesses to our inquiry stressed that the onus of the definition should be on the human movement of a species, rather than those that have moved on their own accord; so the expansion of a species from mainland Europe into the UK would not be considered a non-native species.6 Dr Paul Walton from Wildlife and Countryside Link, told us why the distinction is important:

… [INNS are] explicitly those species that have been directly moved by human agency. That can be deliberately through the pet trade and people releasing their terrapins into ponds in Glasgow… There are also the hitchhikers, such as flatworms arriving on pot plants. These are species that are moved by direct human agency, and that is really what we need to focus on. It would be a mistake if we were to confuse these two issues and spend our time, effort and resources trying to stop species that are arriving here through climate change.7

5.Others argued that although species that have arrived through climate change may not be considered INNS, their possible impact on the UK should still be assessed and monitored.8 Climate change is likely to change the areas from which INNS could come, and their range within the UK, the number of species and their composition.9

Impacts of invasive species

6.INNS harm biodiversity, animal, plant and human health and bring large economic costs. They are one of the main drivers of global biodiversity loss after land/sea use change, direct exploitation, climate change and pollution.10 The 2019 UN global assessment report on biodiversity concluded that the numbers of invasive species per country have risen by around 70 per cent since 1970.11 INNS have contributed to 40 per cent of the animal extinctions that have happened in the last 400 years and are the biggest threat to biodiversity on islands.12 The number of INSS in the UK and its Overseas Territories is among the highest globally and their presence is growing with the expansion of international trade, transport and travel.13 We heard that around ten new species become established in the UK each year, and on average, two of these may become invasive.14

7.INNS affect plant and animal health. For example, signal crayfish are the main cause of the rapid decline in native crayfish through transmission of crayfish plague. Livestock diseases are known to be carried by invasive ticks and mosquitos. The ash dieback epidemic, caused by a non-native fungus, is predicted to kill half of the UK’s native ash trees with a cost of £15 billion over the next 100 years.15 Invasive plants can also affect the physical environment and ecosystem function. Himalayan balsam can exacerbate the erosion of riverbanks and Japanese knotweed undermines the structural integrity of buildings (figure 1). These species also outcompete native plants.16

Figure 1. Himalayan balsam outcompeting native wildlife on a river bank.17

8.A small proportion of non-native species established in the UK harm human health. Some of these can be serious such as the spread of Lyme disease by non-native deer, giant hogweed which causes skin rashes and blistering, and the oak processionary moth, whose caterpillars can cause skin irritation and breathing difficulties. The INSS posing the greatest threat to human health are mosquitoes and ticks.18 Future threats to the UK are also posed by the Asian tiger mosquito (which carries human diseases, including chikungunya and dengue fever) and the Asian hornet which can cause anaphylaxis.19

9.During our inquiry, organisations highlighted the economic costs of INNS to their operations. The City of London Corporation told us it spent close to £100,000 tackling the oak processionary moth across its open spaces last year and DEFRA’s eradication of the Asian longhorn beetle in Kent in 2019 cost approximately £2million.20 Thames Water is planning to spend £4.7 million over the next five years and South West Water and several other water companies are investing around £2 million on invasive species management.21 The water industry’s research body (UKWIR) concluded that unless action is taken now, the costs to the environment and the economy from INNS will increase exponentially.22

Governance of invasive species

10.Major international agreements dealing with INNS have been ratified by the UK including the Bern Convention and the Convention on Biological Diversity (CBD), which require parties to prevent their introduction.23 The Aichi Targets, which fall under the CBD, include a commitment by 2020 that INNS and their pathways are identified and prioritised, priority species are controlled or eradicated, and pathways are managed to prevent species’ introduction and establishment. In 2019 the Government admitted its progress on meeting this target was “insufficient”.24

11.The European Commission co-ordinates activity on invasive species across the EU. Since our last inquiry, the EU Invasive Alien Species Regulations have come into force to control INNS entry and spread across the Single Market.25 It has a three-pronged hierarchical strategy of prevention, early detection and rapid eradication and, finally, management. This recognises that prevention is more cost-effective and better for the environment than dealing with an already-established invasive species.26

12.At the core of the EU regulation is the list of Invasive Alien species of Union concern (see Annex).27 Listed species are subject to restrictions on keeping, importing, selling, breeding and growing. Member States are also required to take action on pathways of unintentional introduction, to take measures for the early detection and rapid eradication of these species, and to manage species that are already widely spread in their territory.28 There are 49 species listed: 26 animals and 23 plants.

Domestic legislation

13.Domestic legislation and regulation of non-native species in the UK is scattered across a large number of overlapping legal frameworks.29 Introduced prior to the EU regulations, the Wildlife and Countryside Act 1981 (WCA) is the principal legislation dealing with non-native species.30 The WCA makes it illegal to release or allow to escape into the wild any animal, or to plant or grow in the wild any plant, that is listed in Schedule 9 to the Act. The Natural Environment and Rural Communities Act (NERC) 2006 amended the WCA 1981 and gave the Secretary of State powers to ban the sale of invasive non-native species known to cause damage to wildlife in England and Wales. Subsequently, the Infrastructure Act 2015 amended the WCA to put in place powers to issue species control agreements and species control orders.31

Government coordination

14.Invasive species are a devolved policy matter in the UK, although they are not bound by borders. The Government established the Great Britain Non-Native Species Secretariat (GBNNSS) in 2006 to help coordinate work across England, Wales and Scotland.32 There has been a GB-wide strategy since 2009 with the latest version published in 2015.33 Northern Ireland works with the Republic of Ireland in an All-Ireland Forum, on a whole island basis. Professor Peter Robertson from the University of Newcastle, suggested that the remit of the existing GB Programme Board should be broadened to include Northern Ireland, while maintaining a dialogue through the All-Ireland Forum.34

15.Dr Niall Moore, chief non native species officer at DEFRA, explained that the Government has four biosecurity regimes: animal health, plant health, aquatic animal health (fish health) and bee health. He said these biosecurity regimes had been around for decades, whereas those for invasive species were 40 to 70 years behind.35 Lord Gardiner’s responsibility for biosecurity was only added to the Ministerial role in July 2016. He acknowledged that there was much more to be done:

Invasive species have not had the recognition that animal, plant and bee health have had. […] This is an area where we are being damaged and we are being damaged because we have not been rigorous enough with it in previous decades and indeed previous centuries. We have been sleepwalking, in my view, over the last 100-plus years.36

16.The Government has missed its legal targets on invasive species, and we are concerned that they are not receiving the same priority and funding as animal and plant health regimes. We welcome the Government coordinating work on invasive species across England, Wales and Scotland. We recommend it should review whether this should be extended to include Northern Ireland given its lack of executive.

1 Q1 [Professor Roy], Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). 2019. Global Assessment Report on Biodiversity and Ecosystem Services

2 Invasive Species Ireland. 2013. Demonstrating the costs of invasive species to Britain; Williams et al. 2010. The Economic Cost of Invasive Non-Native Species on Great Britain, CABI; Wildlife and Countryside Link (INV0020); Committee on Climate Change, Adaptation Sub-Committee (INV0049)

3 Environmental Audit Committee. 2014. Invasive non-native species, Fourteenth Report of Session 2013–14, HC 913

4 Great Britain Non-native Species Secretariat (GBNNSS). 2019. Definition of terms. [Accessed 03/05/2019]

5 Q1 [Professor Roy]

6 Q1 [Professor Roy]; Q26 [Dr Walton]; Q76 [Dr Dunn]

7 Q26; see also British Ecological Society (INV0054)

8 British Ecological Society (INV0054)

9 CABI (INV0053)

11 IPBES. 2019. Global Assessment Report on Biodiversity and Ecosystem Services. Across the 21 countries with detailed records

12 Convention on Biodiversity. Island Biodiversity [Accessed 23/05/2019]

13 Biosecurity Research Initiative at St Catharine’s (BioRISC) (INV0039)

15 Hill et al. 2019. The £15 billion cost of ash dieback in Britain. Volume 29, Issue 9, 6 May 2019,

17 Courtesy GBNNSS

18 Public Health England (INV0083)

19 Defra (INV0035); Public Health England (INV0083)

20 City of London Corporation (INV0055); Defra (INV0035)

22 Anglian Water Services (INV0050)

23 The Council of Europe’s Convention on the Conservation of European Wildlife and Natural Habitats (1979), or Bern Convention, introduced inter-governmental cooperation towards controlling the spread of and eradicating INNS in Europe through the creation of a dedicated Group of Experts since 1992. Law Commission. Wildlife law

25 Regulation (EU) No 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. (The IAS Regulation)

26 Centre for Ecology & Hydrology (INV0027)

27 GBNNSS. 2019. Legislation in England and Wales [Accessed 14/05/2019]

28 European Commission. List of invasive alien species of Union concern [Accessed 05/05/2019]

29 Law Commission. Wildlife law, p322 [Accessed 20/05/2019]

30 GBNNSS. 2019. Legislation in England and Wales [Accessed 14/05/2019]

31 Wildlife and Countryside Act, Schedule 9A. Other legislation covering INNS includes the Animal Health Act 1981, Destructive Imported Animals Act 1932, Dangerous Wild Animals Act 1976, the Bees Act 1980, Environmental Protection Act 1990, Conservation of Habitats and Species Regulations 2010, Countryside and Rights of Way Act 2000, Import of Live Fish (England and Wales) Act 1980, Plant Health (England) Order 2005, Plant Health (Wales) Order 2006 and the Plant Health (Wales) (Amendment) Order 2008. Environment law. Introduction of non native species into UK wildlife. [Accessed 20/05/2019] and Law Commission. Wildlife law [Accessed 20/05/2019]

32 The GBNNSS covers policy and ministerial support, risk analysis, communications and the overseas territories with a team of 4.2 full time equivalent staff.

33 Defra, Scottish Government, Welsh Government. 2015. The Great Britain INNS Strategy

34 Professor Peter Robertson (INV0042)

Published: 25 October 2019