We are frequently asked the same questions about invasive non-native species (INNS). We have tried to answer these and other common questions below. If you cannot find the information you need below or elsewhere on our website, get in touch.

How many non-native species are there in Great Britain?

The Department for Environment Food and Rural Affairs (Defra) states that there are nearly 2,000 established non-native species in Great Britain.

Are all non-native species a problem?

The majority of non-native species do not cause any problems. Very few of them have a negative impact on our economy, health or environment. In London particularly, the landscape is full of ‘naturalised non-natives’ that perform important landscape and ecological functions. This is why it is crucial to identify which non-natives have potential to become invasive so they can be managed appropriately.

What is an invasive non-native species?

A full description and further information is available here.

What are the priority invasive non-native species of concerns in London?

Information on the priority invasive non-native species of concern in London can be found here.

Is the invasive non-native species issue getting better or worse?

It is generally expected that the number of non-native species becoming established in London will continue to increase due to growth in global transport and trade, and increased transport efficiency. Industry experts are also concerned that climate change may allow some non-native species currently present in London to become invasive. So the situation is likely to become worse without effective coordination and partnership work to manage this.

Why don’t you include natives that behave invasively in LISIs remit?

Management of invasive non-native species and management of native species behaving invasively are very different issues. Invasive non-native species require co-ordinated landscape-wide effort, with emphasis on preventing them from establishing in the wild. Natives that behave in an invasive way do so in response to human-induced changes and are individual site management issues.

Eradication or large-scale management is not an objective for these native species. Their management needs to be considered on a site-by-site basis as they can perform important ecological functions.

My neighbour has Japanese knotweed on their property. What can I do?

This is a very common question. As a first step it’s a good idea to introduce yourself to your neighbour, this way you can also introduce them to Japanese knotweed. Most people are not aware what the plant looks like or the problems associated with it. Once they know the impacts, they may be willing to remove it. You may need to remind them that we all have responsibilities under the Wildlife and Countryside Act 1981 to not allow the species to be planted or to grow in the wild. It is always worth getting in contact with your local council to see if there is anything they are able to do to assist.

Once all other reasonable action has been taken to address this issue together you might have to look further. Currently Japanese knotweed can be included under ‘public nuisance’. This is where an action or lack of action leads to an interference with, disturbance of or an annoyance in the exercise of enjoyment of ownership or occupation of land. This includes vegetation which passes boundaries and so can include Japanese knotweed. Although, as with most legal issues this is a complicated topic and you may need to seek further legal advice.

I have Japanese Knotweed growing on my property what can I do?

The first thing to do is make sure you have identified it correctly. Identification information and sheets can be found both here on the LISI website or at the Great Britain Non-native Species Secretariat website. If you are sure you have knotweed you need to decide whether this is something you are going to treat yourself or if you are going to get a professional contractor to treat it for you. Information to help you select a contractor can be found here while treatment information can be found here.

After any treatment, it is important to keep an eye on the site as it will grow back. Several years of repeated treatment will usually be necessarily to stop it from re-growing. Even after this time, you still need to be very careful not to disturb the soil as it can grow back from dormant rhizomes underground. Because of this it is important to report your sightings which you can do on the LISI website.

Where can I go to get more information?

We have tried to provide as much information as possible on this website but understand that, as invasive non-native species management can be complicated, you may need some more specific information.

The Great Britain Non-Native Species Secretariat website has additional information about a range of invasive non-native species. The Environment Agency and Defra also have further information. If you require assistance with something specific, get in touch with us at LISI.