Statistics and facts


The total loss to the world economy as a result of invasive non-native species has been estimated at 5% of annual production (Pimentel et al, 2002).

Globally, INNS have contributed to 40% of the animal extinctions that have occurred in the last 400 years (CBD, 2006 (external link)).

Over 80% of the worlds islands have been invaded by rodents (Atkinson, 1985).

20-30% of all introduced species worldwide cause a problem (Pimentel et al 2001).

10 billion tonnes of ballast water is transported around the world every year (IMO, 1997).

84% of the world's 232 marine ecoregions reported the presence of invasive non-native species (Molnar et al, 2008 (external link)).

Introduction rates have been reported as high as two to three new species per year for Port Phillip Bay, Melbourne, Australia and up to one species every nine weeks for San Francisco Bay, California, USA (WWF International, 2009 (external link)).

In Europe, approximately ten new species become established each year and there is a rising trend for invertebrates and marine fish introductions (Hulme et al 2009).

The average lag-phase (time between introduction and successful spread and impact of a species) has been estimated at about 50 years, with a shorter lag-phase for tropical species than temperate species (Daehler 2009).

Great Britain

The total annual cost of invasive non-native species to the British economy is estimated at approximately £1.7 billion. This is said to be a conservative figure and does not include indirect costs which could be substantially higher (Williams et al, 2010 (PDF)).

Estimated total annual costs of invasive non-native species to England is £1,288,262,000, to Scotland is £250,144,000 and to Wales is £132,244,000 (Williams et al, 2010 (PDF)).

Almost two thirds of our non-native plant species in England are of European origin. The next most frequent continent of origin for terrestrial and freshwater plants is North America. Non-native freshwater fish species in GB originate mainly from North America and European/Asian continent equally. Australasia is the origin of 38 animals 9 plants that have become established in GB (Roy et al, 2012 (PDF)).

Plantlife's 'Dirty dozen' invasive non-native species (external link) which threaten the UK's flora include:

American skunk cabbage (Lysichiton americanus)
Broad-leaved bamboo (Sasa palmata)
Giant rhubarb (Gunnera tinctoria)
Cotoneasters (Cotoneaster spp)
Himalayan Balsam (Impatiens glandulifera)
Hottentot fig (Carpobrotus edulis)
Japanese Knotweed (Fallopia japonica)
Pirri-pirri bur (Acaena novae-zelandiae)
Rhododendron (Rhododendron x superponticum)
Spanish bluebell and hybrid (Hyacinthoides hispanica and H. hispanica x H. non-scripta)
Variegated yellow archangel (Lamiastrum galeobdolon subsp. argentatum)

The UK Technical Advisory Group on the Water Framework Directive have listed aquatic non-native species according to their level of impact.

Japanese Knotweed

Total annual costs of Japanese knotweed to the British economy is estimated at £166 million (Williams et al, 2010 (PDF)).

Total annual cost of Japanese knotweed control at riparian habitats (excluding lakesides) in Great Britain was estimated at £5,636, 698 (Williams et al, 2010 (PDF)).

£2m was spent to eradicate Japanese Knotweed on one 2 hectare development site (Williams et al, 2010 (PDF)).

9.2% of rivers and canals in England and Wales are infested with Japanese knotweed and 3.1% in Scotland (Williams et al, 2010 (PDF)).

The total cost of controlling Japanese knotweed on the road network in Great Britain is estimated to be £5,095,894 (£3,901,393 in England, £437,416 in Wales and £757,085 in Scotland) (Williams et al, 2010) (PDF)).

An insect called a psyllid is a new bio-agent to control Japanese Knotweed. Using an insect - which is a predator of the plant in Japan - to act as a natural form of pest control, will be the first time that a solution like this has been used to help control the spread of a non-native invasive plant in Europe and, if successful, could reduce the costs to the building and engineering industries of clearing this invasive plant. CABI – a world expert in natural control methods – have carried out extensive research into the best way to combat Japanese Knotweed with the least impact on the environment.  The psyllid was found on Knotweed growing wild in Japan and has now been tested in the UK on over 90 types of plants, focussing on closely related native species as well as important crops and ornamental species to ensure it does not attack other plants.  If the first phase is successful, the psyllid will be released at further sites where it will continue to be monitored (Cabi, 2014 (PDF)).

Japanese Knotweed is listed by the World Conservation Union (IUCN) as one of the world's 100 worst invasive species (external link).

Japanese Knotweed grows vigorously at a rate of up to a metre a month, including through tarmac, concrete and drains, causing damage to roads and buildings costing the millions of pounds to remove each year (Cabi, 2014 (PDF)).

Other species

£13.9m of damage per year estimated to be caused by deer vehicle collisions (many of which were non-native species) (Lanbgein & Putman, 2006 (PDF)).

£11m estimated to be the cost that would be required to eradicate rhododendron from a national park in Wales (Postnote, 2008 (PDF)).

£100,000 spent by one water works on modifications to cope with Zebra Mussels (Williams et al, 2010 (PDF))
£10m estimated cost to British timber industry of squirrel damage to beech, sycamore and oak woodland (Booy et al, 2008).

£1m delay was caused to a road development scheme while waiting to treat Japanese Knotweed (Booy et al, 2008).

A Scottish Government Scottish Government Report (external link) estimated the potential Net Economic Value loss to Scotland of the introduction of the salmon parasite Gyrodactylus salaris at £633 million with severe consequences for rural communities.

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