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About non-native species

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What are invasive non-native species?

Watch our video to learn more about invasive non-native species, their impacts, and how they are spread.

Over 2,000 plants and animals have been introduced to Great Britain (GB) from all over the world by people. These are known as non-native species. Most non-native species are harmless but around 10-15% become invasive non-native species which spread and have a harmful impact.

Invasive non-native species are one of the top five drivers of global biodiversity loss and play a role in 60% of plant and animal extinctions. They cost the global economy over $423 billion a year and their costs have quadrupled every decade since 1970.

Here in GB they threaten the survival of native wildlife, damage our natural ecosystems, cost the economy nearly £2 billion a year, and can even harm our health and interfere with activities we enjoy. 

Our natural world is already under pressure from other drivers of biodiversity loss such as climate change and habitat destruction, which reduce the ability of native wildlife to cope with these pressures and vice versa. Climate change is also likely to increase the ability of new invasive species to establish and allow other non-native species which are already present in Britain, but not yet having a negative impact, to become invasive.

How are they spread? 

Non-native species can be introduced to an area outside their native range both deliberately, for example as ornamental plants to be used in our gardens, or exotic animals to be kept as pets, or as accidental ‘hitch-hikers’, for example with goods transported from overseas, or with tourists returning from a holiday abroad.

Once they have been introduced most non-native species will not spread into the wild, or if they do, they are not likely to become widespread or have a noticeable impact. However, many invasive non-native species can be spread very easily as they produce large numbers of eggs, young, seeds, spores or fragments that are often tiny and sometimes microscopic. These are known as ‘propagules’, and, for some invasive species, it only takes one to start a new invasion.

Propagules can be spread on equipment, vehicles and clothing, or in the movement of soil, water or garden waste. You could accidentally be spreading them without realising through your work or hobbies. Find information below on how you can help prevent the spread of invasive non-native species while taking part in the following activities:

Why are they a problem?

Impacts on the environment

Here in GB invasive non-native species threaten the survival of native wildlife and damage our natural ecosystems by preying on or out-competing other plants and animals, disrupting habitats and ecosystems, and spreading harmful diseases.

Some environments are more vulnerable to invasion than others. While freshwater and marine species make up only a small proportion (less than 5% each) of all non-native species in Britain, they are much more likely to become invasive than terrestrial species.

Small islands, including those around the UK and many of the UK Overseas Territories, are hotspots for biodiversity but the wildlife they support is particularly vulnerable to the impacts of invasive species having evolved away from many predators, competitors, and diseases. Since 1500 72% of global extinctions have occurred on islands and invasive species have contributed to 86% of these extinctions.

Our natural world is already under pressure from other factors including climate change and habitat destruction, and invasive species reduce the ability of native wildlife to cope with these pressures and vice versa.

Impacts on the economy

Invasive species cost the GB economy nearly £2 billion a year, affecting us all. Costs include damage to buildings and infrastructure, interference with the production of food and materials, losses to other activities such as tourism and navigation, and high management costs for established invasive species. Japanese knotweed alone is estimated to cost the GB economy around £250 million per year.

Impacts on our health and way of life

Invasive species can be a significant nuisance. Some are irritants of our skin or respiratory system, cause road traffic accidents, or are pests in our homes. Others increase our risk of being flooded or prevent us from enjoying recreational spaces and activities such as angling or kayaking.

Watch our videos to find out how invasive non-native species impact on a range of environments:



Our homes and the places we live

Woodlands and the terrestrial environment

What is being done to reduce the impacts of invasive non-native species?

Once an invasive non-native species has been introduced it can be difficult to manage and the problems it causes will escalate as it spreads further. We need to act fast, if possible preventing the arrival of new non-native plants and animals and, failing that, detecting them and responding rapidly to prevent their establishment once they appear. For well-established species we need to try to minimise their negative impacts, including by slowing their spread.

The GB Invasive Non-native Species Strategy (2023 to 2030) sets out a series of ambitious objectives to guide government, voluntary organisations, NGOs, researchers, businesses and the public to build on the successes of the last fourteen years under previous Strategies.

Examples of the work taking place to reduce future impacts of invasive non-native species include:


  • Horizon-scanning work to identify future threats
  • Risk analysis to assess which species are likely to become a significant problem
  • Contingency planning for new introductions
  • Pathway Action Plans for key pathways of introduction of non-native species, to prevent or manage the risk.
  • Targeted awareness raising campaigns (Check Clean Dry and Be Plant Wise) sharing how the public can help to prevent the spread of invasive non-native species.
  • Legislation to prevent harmful species from being introduced. Download posters with invasive non-native animals and plants of special concern.
  • A pilot Non-native Species Inspectorate which aims to raise awareness of biosecurity, collect data on non-native species risks and ensure that legislation is better understood by stakeholders and enforced where necessary.
  • Development of resources including free training to raise awareness of biosecurity.

Detection and rapid response

  • An ‘alert’ system which flags new records of priority ‘alert’ species. Download a poster with alert species to look out for.
  • Citizen science initiatives such as ‘Asian Hornet Watch’ supporting the ‘alert’ system.
  • A rapid response working group overseeing delivery of rapid responses to priority species.

Management of well-established species

  • There is a fantastic network of Local Action Groups carrying out management of established invasive non-native species across GB.

How can I help?

There are five simple things that you can do to help prevent the spread of invasive non-native species. 

Number one and illustration of fishing and kayaking Keep any boats, clothing, footwear and equipment used in water free of invasive non-native species – remember to Check Clean Dry after use.  
Number two and illustration of wheelbarrow and leaf Be Plant Wise and don't let your garden, pond, or aquarium plants enter the wild.
Number three and illustration of fish tank and paw prints Take care of your pets, never release them or allow them to escape into the wild. It’s cruel and could harm other wildlife. 
Number 4 and illustration of phone and magnifying glass looking at a beetle Look out for Asian hornet and other alert species and record your sightings. Download a poster of alert species and read more on Asian hornet and how to report sightings.
Number 5 and illustration of a woodland and a group of people together If you enjoy being outside consider volunteering with a Local Action Group working on invasive species management. 


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