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What have Hebridean Hedgehogs and Himalayan Balsam got in common?

Posted: Wednesday 31st August 2016 by RiverSearch

Great things can happen when we work together and this July groups from across Surrey waged war on the plant taking over our river corridors, with some fantastic results.

If you have walked along any one of Surrey’s rivers or streams recently there is a relatively high chance you have come across a glorious display of pink flowers along the banks. The plant in question is of course Himalayan Balsam. Himalayan balsam is native to the west and central Himalayas and over millennia has carved out a niche for itself amongst the countless other plants in that region, but like the hundreds of hungry hedgehogs introduced to the Hebrides, Himalayan balsam is a menace to other species outside of its normal geographical range.

The plant is an annual, meaning it completes its life cycle within a year, leaving a seed bank in the soil to grow up the following year. It has a very clever strategy of colonising new areas by using exploding seed pods to fire up to 800 seeds per plant into the surrounding landscape and often into the nearest river, which obligingly transports them downstream before depositing them.

The main issues are that during the summer balsam will grow in dense clusters shading out our native species, before rotting away over winter, leaving bare river banks that are easily eroded away. Most frustratingly for those of you who regularly visit the river is its ability to hog the view on a sunny summers day or make access impossible altogether.

The problem is not a new one and countless hours have been spent over the years by conservation organisations and volunteer groups religiously pulling the plants up each summer. Surrey Wildlife Trust runs its own Invasive Species Week every year tackling this species across the county’s river network. However this effort is such a small drop in such a very large ocean it soon became apparent that a new approach was needed. With this in mind an invasive species month in July 2016 was held instead. “Three weeks longer” I hear you scoff, and you’d be right to, for an extra 3 weeks would hardly make much more of a dent. The difference this time however was how it was run. Rather than going it alone, we contacted as many groups and organisations as possible from across Surrey to either run their own task days or let us advertise tasks they already had planned. The result was 27 different task days running across both the Wey and Mole river catchments involving 17 different groups/organisations and roughly 300 volunteers.


Looking closely at a couple of examples from the month we can begin to see how effective this strategy could be.

The first example took place along the Hoe stream, which rises on Ash ranges close to the Surrey Wildlife Trust HQ, before flowing along to Fox Corner up through Mayford and Woking and finally meeting the river Wey at Pyrford. Fox Corner community nature reserve has been hit hard by balsam, but this year the 1st Brookwood scouts provided 20 volunteers to assist community group members in tackling the weed along the river corridor. Just down the road in Worplesdon a tributary of the Hoe, known as the Whitmoor Vale stream, is providing a steady supply of balsam seeds to the nearby Whitmoor Common Special Area of Conservation. Keeping balsam at bay in these areas is of the utmost importance as it could degrade rare habitats. So Surrey Wildlife Trust were joined by Worplesdon Parish Council, staff from Affinity Water and staff from the Environment Agency to tackle the balsam at the top end of the stream.

Further down the Hoe stream at Mayford Meadows, the Woking Biodiversity Group got stuck into the balsam along the banks and were joined by a couple of interested local residents. A second task day was soon organised between the 2 groups with the Mayford Village Association providing 19 volunteers and clearing virtually all balsam along the banks of the stream between them. The groups have now decided to make this an annual event to stay on top of the balsam and control it in adjacent areas upstream.

The second example jumps over to the Mole catchment where 5 different groups tackled balsam over roughly 14km of the river Mole between Brockham and Cobham. At the upstream end Noel Humphries of British Canoeing has been working away over a number of years to clear balsam in the Brockham area. His efforts have cleared the Burough Bridge area and work from local scouts has almost eradicated it from a nearby woodland. Heading downstream, National Trust ranger David Benjamins ran a task day at Boxhill. Down to Norbury Park now where Wildlife Trust volunteers worked with ranger Andrea Neal over a number of days to clear 4km of river banks. Next downstream was the river Mole Working Group, coordinated by Caroline Cardew Smith , whIch used canoes to tackle balsam along the banks and on the islands between Thorncroft bridge and Fetcham Splash, as well as pulling out a good amount of litter as they went. At Fetcham Splash the Lower Mole Countryside Partnership, headed by Conor Morrow, got stuck into 3 task days, working down river to the boundary of the River Mole Local Nature Reserve.

Working together at the catchment scale like the examples above will be our most effective weapon in eradicating balsam. As the Mayford Village Society have shown there are individuals and groups all over Surrey who want their rivers back and just need a little help to get started. The task of eradicating balsam is so large it simply cannot be carried out solely by local authorities and organisations. It needs local communities to not just run their own task days but to provide local knowledge, speak to local landowners and take charge of their own stretch of river.

Invasive Species Month 2016 showed that this is possible and by empowering local communities living along the river we can start to get on top of this problem.

List of other groups and organisations involved.

Guildford Borough Council – Rangers Alison Boyce and Nick Rowe ran tasks at Chilworth Gunpowder Mills and Shalford Water Meadows
Waverley Borough Council, -Ranger Victoria Huth helped bring the month together.
Rangers Robin Crowther , Steve Webster and James Caldwell ran task days at Farnham Park, Tilford and Godalming
Mole Valley District Council -The Lower Mole Countryside Partnership – Ranger Connor Morrow ran tasks at Fetcham Splash along the river Mole and Ashtead Common
RiverSearch volunteer Carole Gale organised and ran for the second year running a task on the Wey at Warren Farm Caravan Park.
David Naisby and Maggie Scott – Carried out tasks adjacent to each other on the Tillingbourne, David with the support of RiverSearch volunteers.
Gatwick Greenspace – Kevin Lerwill ran task days on the Mole and the Gatwick stream near the airport.
Volunteer trainee ranger Matthew Sharp ran a task at Papercourt Marshes removing Candian Golden Rod

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