Tag Archives: INNS

It’s Invasive Species Week!

What are they and how can you help ‘Stop the Spread’?

Invasive species are non-native animals and plants (terrestrial, freshwater and marine) that have established themselves in the UK and are causing problems for our native wildlife and ecosystems. Invasive non-native species (INNS) are globally recognised as a major threat to biodiversity, second only to habitat loss. Economically, their impact is also highly significant. A recent study in the UK concluded that the direct cost of controlling these species is at least £1.7 billion every year, with researchers admitting that this is likely to be a gross underestimate. This week we are trying to raise awareness of the problematic invasive species found in our rivers here in the South East and what you can do to help.

Exotic plants have been introduced to the UK for centuries! Plants that now seem commonplace to us were once brought here from far and wide for their attractive flowers or leaves, medicinal qualities or for food. Not all of these are a problem, and the benefits they have brought with them far outweigh any negatives. However, some of them have aggressive seed dispersal, are fast growing and aren’t eaten by any animals in the UK, meaning that they can out compete our native flora and take over.

Rivers can act like corridors for dispersal of seeds, which means that dense populations of these troublesome plants can often be found clogging rivers and dominating plant life along the banks. You can find out about the BIG FOUR invasive plant species we have here in the South East on our website: www.wandletrust.org/invasive-species/the-big-four/

The GB Non-Native Species Secretariat is a national body with a responsibility for helping to coordinate the approach to INNS in Great Britain. We encourage you to follow their advice and ‘be plant wise’ when choosing plants to go in your garden to help stop the spread of invasive species: http://www.nonnativespecies.org/beplantwise/.

Our amazing team of River Rangers have just completed their first INNS survey on the River Wandle for 2018. These surveys help identify and locate INNS on our waterways which allows us manage their removal in the long term. If you’re interested in becoming a River Ranger please get in touch on volunteers@southeastriverstrurst.org.

But it’s not just plants that are having a big impact on our rivers: animals introduced in the past are also now playing havoc with the natural balance of life. With no predators these species can take over, spreading disease and competing with native wildlife for food and resources.

A classic tale is that of American signal crayfish which was introduced the 1970s for export to Scandinavia where it’s a sought-after food. Unfortunately, they are carriers of crayfish plague and they can pass this deadly disease to native white-clawed crayfish whilst remaining healthy themselves. The signal crayfish is much larger than its native relatives and is a voracious predator feeding on a variety of fish, frogs, invertebrates, plants, and even eating other signal crayfish. It didn’t take long for the signal crayfish to escape from commercial fisheries and begin to outcompete their UK cousins for habitat and food.  Since their introduction they have decimated the native crayfish populations wherever they are present, and cause further problems by burrowing into river and canal banks causing erosion, bank collapse and sediment pollution. There have been anecdotal reports of signal crayfish spotted on the Hogsmill River recently.

You can help stop the spread of INNS like the signal crayfish by following the ‘check, clean, dry’ process on all your clothing and kit after visiting a river: http://www.nonnativespecies.org/checkcleandry/.

Hitchhiking eggs, seeds and disease can be spread between rivers if these rules aren’t followed, having a devastating effect on our wonderful native wildlife. But everyone can play their part in stopping the spread! Please be careful to check, clean and dry after your next visit to the river.

Recruiting: Invasive Non-Native Species Officer

The Wandle Trust (part of the South East Rivers Trust) is recruiting a part-time Invasive Non-Native Species (INNS) Officer to help coordinate and deliver work to tackle aquatic INNS on the River Wandle.

Himalayan Balsam

Himalayan Balsam

INNS can have a negative impact on rivers by both directly out-competing native species and indirectly altering habitats, for example by causing the excessive ingress of silt which can smother the natural gravel riverbed.

The post is supported by the National Lottery through the Heritage Lottery Fund and is part of the Living Wandle Landscape Partnership, a programme which involves the local community in the restoration and enhancement of the River Wandle landscape.

The Project Officer will be responsible for the day-to-day implementation of the River Wandle Invasive Non-Native Species Action Plan and Work Programme.  The role will involve both coordinating the work of a range of partners and contributing to the delivery of the INNS Work Programme.

This post is now closed.

A selfish shellfish!

The invasive quagga mussel (Dreissena bugensis) has been found in the Thames Catchment on the River Colne!

What is the quagga mussel?Quagga Mussel

The quagga mussel is an invasive freshwater filter-feeder with an extremely large capacity to filter water and the ability to grow large dense populations. When established, these combined traits can result in a reduction in the availability of nutrients and oxygen to our native aquatic wildlife, damaging a freshwater ecosystem.

Economically, the quagga mussel is a big problem as well. With its prolific breeding, this invasive mussel can clog water pipes, filters and turbines damaging our infrastructure. Furthermore it disrupts recreation, fishing and aquaculture industries by growing on equipment and boats.

All in all, it is not a welcome sight!

What can be done about it?

Currently there are no recommended methods for controlling populations of this mussel. Therefore our only option is prevention.

Biosecurity needs to be increased in the Thames Catchment to ensure the mussel isn’t accidentally transferred to our other river systems. For more details on how to step up your biosecurity – visit Check Clean Dry.

To find out more about the quagga mussel’s impact outside its native range, take a look at this video from North America where this mussel, and its relative the zebra mussel, have already had a devastating impact.

Image credit: Quagga mussel – GBNNSS

New book: The Pocket Guide to Balsam Bashing

Pocket Guide to Balsam Bashing

We are very excited to announce the recent publication of a new book by our Chairman of Trustees, Theo Pike, entitled ‘The Pocket Guide to Balsam Bashing – and how to tackle other Invasive Non-Native Species’.

This ground-breaking 96-page handbook includes more than 40 invasive non-native species (INNS) such as Himalayan balsam, giant hogweed, Chinese mitten crabs, signal crayfish and mink, with practical advice on how individuals and community groups like ours can take action against them or stop them spreading further.

Even reporting a sighting of oak processionary moths or Asian longhorn beetles can make a big difference to protecting our natural biodiversity, and there is also a section on biosecurity measures like Defra’s Check-Clean-Dry advice.

Copies of the ‘Pocket Guide to Balsam Bashing’ are available direct from the publishers, Merlin Unwin Books, or you can buy a signed copy from Theo at one of our community balsam bashing and  river cleanup events on the Wandle or Hogsmill!

Balsam bashing: Hogsmill River: July 2013

As part of Defra’s initiative to improve rivers across south London (and indeed nationwide) we recently secured funding from the Catchment Restoration Fund for habitat improvements on our sister chalkstream, the Hogsmill, which rises in Ewell and enters the Thames in Kingston near the Rose Theatre.

Before any improvement works can take place, something needed to be done about the enormous amounts of Himalayan balsam growing on the banks.


So, on a sweltering Sunday, and with the blessing of Thames Water on whose site we would be carrying out the balsam removal, 20 of us were admitted through the gates of the sewage treatment works in Lower Marsh Lane.

Having signed us in at the office, Kristine Boudreau, the Hogsmill Nature Reserve Manager, gave us all an induction briefing, and after we had collected our hard hats and hi viz vests, we walked from the building to the site where we were going to begin our work.


Discarding our hats and hi viz vests, we used ladders to get access to the river and began two tasks:  pulling up the balsam, and  removing rubbish, the presence of which was made all the more baffling because the Hogsmill, unlike the Wandle, is not easily accessible.

Hippo and builders’ bags full of balsam stems were dragged up the bank by Roger and JOB, and barrowed away to an ever increasing pile.  Alongside it, we began to stack the rubbish.

Positively gasping in the 30 degree heat by 1 o’clock, we donned our hard hats and hi viz vests once again and walked back to the office where, in the conference room, Jo had prepared tea, coffee, cheese scones and muffins.  It was quite strange to be inside for our refreshment break, but great to have hot and cold running water and kitchen and lavatory facilities!

Ellora, our youngest volunteer that day, declared in true Great British Bake Off fashion that the muffins were ‘light and fluffy’.

Back we trekked across the treatment works for our afternoon shift.


Gideon and Robin decided to tow a couple of half barrels upstream, taking photographs of the graffiti under the bridge…

… and exploring the twin tunnels under Berrylands station.

Finally, mindful of bio-security, we carried out ‘check-clean-dry’ to prevent any spread of invasive species by our equipment, particularly waders and Wellies which had been worn in the water, but also the trugs, ropes, tools and the tyres on the wheelbarrows.

It was easiest to make sure all waders were cleaned while people were still in them…

… and we ensured we’d removed all the mud from them first in order for the spray disinfectant to be effective.

Before we departed, we had a look at where we had been working, and felt that we had at least made a small dent in some of the Himalayan balsam!

Thanks to:  Abi, Andy, Chris, Ellora, Gideon, Jo H, Jo S, John L, John O’B, Jonny, Kristine, Martin, Neil, Nick, Robin, Roger, Rory, Toby and Thomas

Who removed:   1 shopping trolley, 1 push chair, 1 push chair frame, 1 bucket, 1 wheelbarrow without a wheel, 1 plastic crate, 1 bicycle wheel, 1 inner tube, 1 garden chair frame, 2 bicycles, 2 motorbikes, several bin bags of light litter, plus a couple of tonnes of Himalayan balsam.

This event was supported by Thames Water