This week is Invasive Species Week, running from 27th March through to 2nd April.  The aim is to raise awareness about what invasive species are and the problems they cause. The total annual cost of invasive species to the British economy is estimated to be around £1.7 billion (Williams et al, 2010), so it’s easy to see why they are a big issue!


American mink were introduced to Britain in the fur farming trade and have become widespread throughout Britain, predating on native species including water voles and birds. Photo © Darin Smith

So, what are invasive non-native species? Firstly, non-native species are those that have been introduced (i.e. by human activity) to areas outside of their natural distributional range, and can include any part of a species, such as its eggs, seeds or propagules, that may survive and reproduce. A non-native species is then classed as invasive when it has the ability to spread and subsequently reproduce on a scale that can cause damage to the environment, our economy, our health and the way we live.

Signal crayfish has negatively impacted upon our native white-clawed crayfish population through direct competition and the spread of disease. Photo © WWT

Some of the main invasive non-native species (INNS) to occur in Wiltshire come from all over the world and range from mammals such as American mink to invertebrates including the signal crayfish to plant species such as Himalayan balsam, Japanese knotweed and giant hogweed. INNS often out-compete native species or spread diseases, disrupting the ecological balance of our ecosystems and causing further problems; globally, it is estimated that INNS have contributed to 40% of animal extinctions over the last 400 years (CBD, 2006).


Himalayan balsam can form dense stands that stop other flora from growing. Photo © Sue Sawyer

All hope is not lost however! The Water Team are already on the case when it comes to tackling INNS, and you can help too:


Join one of our volunteer ‘Balsam Bashing’ parties

We are strategically controlling Himalayan balsam along our watercourses and you can get involved too. Over the summer we will be holding volunteer work parties every Tuesday from June to August – it’s fun, it’s easy and anyone can join in!

2017 Dates River Location
Tuesday 6th June Whitehill Stream Swindon
Tuesday 13th June Worton Stream Urchfont
Tuesday 20th June River Avon Durrington
Tuesday 27th June River Bourne Laverstock
Tuesday 4th July River Wylye Stapleford
Tuesday 11th July River Nadder Chicksgrove
Tuesday 18th July River Nadder Burcombe


Volunteering can be a great way to meet new people. Photo © Ryan Tabor

All volunteering events meet at 9:30am. As always, we will supply all the necessary safety clothing and equipment, and endless amounts of tea, coffee, hot chocolate and biscuits. However, please can you make sure you bring clothing appropriate for the weather (waterproofs/sunhat), wear sturdy footwear, long sleeved top and trousers to protect from brambles and nettles, and bring a packed lunch and a drink. However, locations are subject to change, so please contact us for precise meeting points: [email protected] or 01380 736066.

Submit your records

You can help us identify where invasive species are occurring across the county. If you spot them, report them to us through our Living Record online wildlife recording system. You can find a step-by-step guide of how to do this here:


It’s not just on our waterways that INNS occur. Keep an eye out for the Asian hornet – this species was first sighted in the UK in 2016 in Gloucestershire and predates on native insects. It has a distinctive dark brown or black velvety body, and has brown legs with characteristic yellow ends. Photo © CharlesJSharp

Follow good practice: Check, Clean, Dry

If you are a user of our waterways (e.g. anglers / sailers / canoers / walkers / surveyors) then follow good biosecurity practices to help stop the spread of invasive species and the diseases they carry. Just remember to Check Clean Dry. Check your equipment and clothing for live organisms; Clean your equipment and clothing, preferably using hot water; Dry your equipment and clothing thoroughly, so as not to transfer species or their diseases to other sites.

c_Matthew Roberts

However you use the waterways, be sure not to spread INNS by checking, cleaning and drying all your equipment. Photo © Matthew Roberts

Be Plant Wise

Do you own a pond? You can help stop the spread of invasive species and Be Plant Wise. Ponds provide a great year-round haven for wildlife, however if you do not use native plant species and care properly for you pond, some commonly available non-native pond plants can take over your pond and become established in the wild, threatening our native plants, clogging waterways and removing oxygen from the water, which can negatively impact other wildlife. Find out more information on how to be plant wise here:


9.2% of rivers and canals in England and Wales are reported to be infested with Japanese knotweed (Williams et al, 2010). Photo © Ben Fitch

Please keep up to date with what we have been up to by following us on Twitter @wiltsrivers

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