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Multi-billion pound bill from ‘nature invaders’
set to soar post-Brexit

26 March 2018

A coalition of conservation charities, coordinated by Wildlife and Countryside Link [1], is warning that action is needed from the Government to tackle the potentially spiralling cost to the economy of invasive plant and animal species post-Brexit. The warning comes as the charities release updated figures showing that invasive plants and animal species cost the British economy well in excess of £2 billion in 2017 [2], and coincides with Invasive Species Week 2018. [3]

As well as the current cost to the economy, post-Brexit changes to trade agreements and biosecurity measures, along with the potential opening up of new trade routes, risks more ‘nature invaders’ getting through our borders. The campaigners are warning that the preventative work of the Government’s Animal and Plant Health Agency (APHA) and the rapid eradication work of the Environment Agency must be better-resourced to defend the UK against invasive plants and animals.

In 2016/17 the Government in England spent £922,000 in relation to invasive non-native species.[4] This forms less than 0.5% of the £217million expenditure of the APHA[5], with just £335,000 spent on early warning and rapid response measures. This is despite preventative and early action being significantly more cost effective than eradication when the species has become established.

Six of the worst invasive species in the UK and their costs to the economy:

Species and damage causedEstimated annual cost to the economy in 2017*
Japanese knotweed is found in almost all British constituencies. It damages habitats, increases soil erosion and flood risk, impacts on railways, highways and buildings, and is expensive to eradicate.over £200 million [6]
New Zealand flatworms prey upon worms and snails, reducing soil fertility and food production. Earthworm numbers are down in some areas by 75%. The impact is worst in Scotland and Northern Ireland. Flatworms and many other invasive species are regularly imported in soil and pot plants.£34 million in Northern Ireland and £23 million in Scotland [7]
Grey squirrels cause: tree damage by bark-stripping, exposing timber to fungal and insect attack; damage to household lofts and cables; and the decline in red squirrels through outcompeting and disease.Over £17 million [8]
Mink threaten poultry and fish farms, they also kill gamebirds, other ground-nesting birds and are responsible for declines in water vole populations, with a 30% fall in water vole sites between 2006-2015Over 6.1 million [9]
Australian swamp stonecrop is one of the most damaging and invasive aquatic plants, forming dense mats which smother other plants. Once established it is almost impossible to get rid of.Over 3.6 million [10]
The North American Signal crayfish has wiped-out whole populations of the native White-clawed freshwater crayfish through predation, competition and transmission of crayfish plague.Over £1.8 million [11]

* Please note that the figures in this table are from a number of studies which have been updated to account for inflation, using the Bank of England inflation calculator. The figures are very likely an underestimate of the cost to the economy as the spread is likely to have increased from the time of the studies referenced. These are determined to be six of the worst invasive species due to their notable spread, damage caused, cost to the economy, and/or their difficulty to eradicate.

Camilla Morrison-Bell, Chair of the Invasive Non-Native Species Group at Wildlife and Countryside Link, said: ‘The number of nature invaders setting foot in the UK is set to grow. Not only can they wreak havoc on our rivers, seas, and countryside, they can cause devastating damage to buildings, infrastructure and produce. Prevention is better than cure, so we need better resourcing for the work of enforcement agencies, backed up with legislation, to tackle the increasing nature invader threat.”

Hannah Freeman, Senior Government Affairs Officer at Wildfowl and Wetland Trust, said: ‘Nature invaders are a big post-Brexit economic threat, which the Government needs to tackle head-on. Robust coordination, strong prevention and enforcement, and a firm legal-underpinning are all essential to turn away harmful nature invaders from our borders.’

Dr Elaine King, Director at Wildlife and Countryside Link, said: ‘Opening our doors to new trade post-Brexit also opens the door to new nature invaders. It is essential that the Government puts the right measures in place to stop harmful species putting down roots and taking a bite out of our economy, otherwise our two billion pound annual nature invader bill could rocket.’

Many non-native plants and animals are harmless, but some become known as invasive when they quickly spread, harming other plants and wildlife. These ‘nature invaders’ are a key post-Brexit risk to the UK economy, as the door could be widened to new invasive non-native species by trade changes. This means a greater risk of non-native species slipping through our borders and new species entering our country that we have had no experience with in the UK, or even Europe, before. This is exacerbated by the Government’s lack of action to enact the Ballast Water Management Convention, ensuring safe disposal and treatment of a key pathway for invasive non-native species.

Existing invaders could also become more widespread by increased trade with countries where these species originate. One example is zebra mussels, which are the most invasive freshwater species in the world – they harm whole food chains, and damage fisheries, aquaculture, water pipes, ship hulls and constructions. They cost water companies about £800,000 a year [12] at present, but in the U.S. they cost the economy well in excess of $5billion per year. [13]

The risk of non-native species, introduced to the UK unintentionally, becoming invasive is also heightened by climate change. Warmer weather conditions mean that species that once would have struggled to survive here, could now thrive and outcompete or kill native wildlife and plants.
The coalition of nature NGOs is calling on the UK Government to safeguard the UK against the rising threat of nature invaders and the associated cost to the economy, by:

  • Carrying out a detailed assessment of the additional post-Brexit ‘nature invader’ threat and ensuring the APHA give greater priority and funding to this growing problem
  • Underpinning the GB Non-Native Species Strategy with the necessary funds and legislation post-Brexit to ensure it is effective, enforceable, and adequately deters illegal activities which could cause invasive species to spread
  • Ensuring that the ‘precautionary and polluter pays’ principles currently in EU legislation are incorporated into UK law. The precautionary principle is essential to give a legal basis to action to prevent nature invaders spreading in the UK, before they cause damage and become established.


Notes to editors:

  1. Wildlife and Countryside Link is the biggest coalition of wildlife and environment charities in England, and operates as part of a UK-wide coalition - Environment Links UK.
    The charities supporting these calls are: Amphibian and Reptile Conservation, Angling Trust, A Rocha, Buglife, Institute of Fisheries Management, National Trust, Plantlife, Rivers Trust, RSPB, Salmon and Trout Conservation, Wildfowl and Wetlands Trust, Woodland Trust.
  2. A report compiled for Defra in 2010 estimated the cost to the British economy of invasive non-native species to be at least £1.7 billion. Using the Bank of England inflation calculator this equates to a cost of £2,072,230,412 in 2017. This is likely to be a considerable underestimate due to the spread of invasive species during this period.
  3. Invasive Species Week runs from 23 March – 29 March 2018. The Great Britain Non-Native Species Secretariat and Defra launched the first Invasive Species Week in 2015. It brings together a range of organisations and individuals to raise awareness of invasive non-native species and the damage they can cause.
  4. In England in 2016/17 the Government spent an estimated total of £922,000 on biosecurity measures relating to invasive non-native species. The overall cost can be apportioned as £145,000 for policy functions, £90,000 on risk analysis, £335,000 for early warning and rapid response measures, £210,000 on coordination, £80,000 on communication and awareness raising activities, and £62,000 on research. Source: Parliamentary Question February 2018.
  5. Animal Plant and Health Agency Annual Report and Accounts 2016-17 p36
  6. Experts calculated the cost to the British economy of Japanese Knotweed to be £165,609,000 in 2010 The Economic Cost of Invasive Non-Native Species on Great Britain. Using the Bank of England inflation calculator this would now cost £201,870,591. This will however be an underestimate as the prevalence of the plant has increased in this period.
  7. Experts calculated the cost to the economy of the New Zealand Flatworm as £29.4 million per annum in Northern Ireland (Christie et al. 2011); and £17 million per annum in Scotland (Boag and Neilson, 2006). Figures update to £34 million in NI and £23 million in Scotland in 2017.
  8. The cost of the grey squirrel to the British economy was estimated to be £14 million in 2010. Increasing this cost in line with inflation this would be £17,065,427 in 2017.
  9. The cost of mink to the British economy was estimated to be £5 million in 2010. Increasing this cost in line with inflation this would be £6,094,795 in 2017.
  10. The control costs for Australian Swamp Stonecrop were estimated in 2010 at £3million (CABI report p115). Increasing this cost in line with inflation this would be £3,656,877 in 2017.
  11. Signal crayfish control and white-clawed crayfish conservation work amounted to £1,502,000 per annum in 2010 The Economic Cost of Invasive Non-Native Species on Great Britain p158. Updated accounting for inflation this figure would be £1,830,877.
  12. p15 2016
  13. The Economic Cost of Invasive Non-Native Species on Great Britain p140

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