It is Invasive Species Week!

This special week was launched in 2015 to help raise awareness of invasive non-native species, and to inspire people and organisations to stop the spread of these detrimental species. The initiative was the idea of the Non-native Species Secretariat and DEFRA since they are estimated to cost the economy £1.7 billion per year.

What’s the difference between native and invasive species?

Native species are defined as species that have colonised naturally in a particular area. Non-native species are those that have been introduced to new areas by man. It is estimated that there are almost 2000 non-native species in Britain: 75% are plants, 22% are invertebrates and 3% are mammals and other organisms. Most of these species are harmless, however 10-15% of these cause negative environmental, economic and/or social problems and are known as Invasive Non-Native Species (INNS).

Which INNS are of relevance to Britain?

Specifically in freshwater environments, INNS of most concern include Himalayan Balsam, Floating Pennywort, Parrot’s Feather, Water Fern, New Zealand Pygmyweed and Water Primrose. These species are incredibly fast-growing and can have severe detrimental impacts on waterways and human infrastructure, leaving them unsuitable for native wildlife and recreational use. They can also pose a significant flood risk. Animals such as American Mink, Signal Crayfish, Killer Shrimp and Ruddy Duck have also had an adverse impact on native wildlife.

Japanese Knotweed is often considered as the most detrimental invasive species as it is incredibly hard to completely remove and can withstand a range of conditions – the rhizomes of this plant can withstand temperatures of below -35°C. Himalayan Balsam is another voracious species which grows in significantly large stands, particularly along watercourses, out-competing native species.

How can they be controlled?

Often it is hard to eradicate these species, however they can be controlled to reduce their spread. This can be via mechanical control (e.g. by cutting down and excavating plants), via chemical methods such as herbicide treatment, or often by a combination of these for more fast-growing species such as Japanese Knotweed. New and novel techniques are also emerging to control these species, such as introducing weevils to control Water Fern.

Want to know more?

We have a large ecology team across the country who can assist in identifying INNS issues on sites and devising site and species specific management plans. If you have any queries regarding INNS please contact Kieran Sheehan or Rob Harrison.



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