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Invasive Species Week 2015

Posted: Wednesday 15th July 2015 by RiverSearch

From the 4th to the 10th July this year we held our 4th annual Invasive Species week and this year the focus was on wetlands. Wetlands are amongst the most species rich habitats in the county but are at particular risk from NNIS displacing native species as they travel down watercourses from different parts of the county.

Non native species have been arriving on our shores for thousands of years many of which were brought here deliberately ,such as crops and garden plants and many others which were stowaways hiding in goods and cargo. The modern globalised world we live in has opened up the four corners of the world to trade dramatically increasing the rate at which non-native species are arriving in this country. A study in 2012 counted 1,875 Non Native Species established in Great Britain, increasing by 10 each year. Roughly 15% of these species have become invasive, that is they are detrimental to our environment, economy, health or social wellbeing. The total annual cost of invasive non-native species to the British economy is estimated at approximately £1.7 billion.

Non-native invasive species (NNIS)are the second biggest threat to biodiversity after habitat loss and it is estimated they are responsible for 40% of animal extinctions over the last 400 years. As a Wildlife Trust we are constantly working to protect the county’s most precious wildlife sites from NNIS and a large part of this is achieved through raising awareness of the threats they pose as well as galvanising volunteers into action to eradicate them.


From the 4th to the 10th July this year we held our 4th annual Invasive Species week and this year the focus was on wetlands. Wetlands are amongst the most species rich habitats in the county but are at particular risk from NNIS displacing native species as they travel down watercourses from different parts of the county.


The week started on Saturday 4th with RiverSearch volunteer Carole Gale running a Himalayan Balsam pulling task at Warren Farm Home Park in Pyrford on the river Wey with 12 volunteers. Himalayan Balsam is a widespread NNIS across our river catchments and is very effective at invading wetlands as its seeds travel down rivers colonising new areas. It out competes our native plants by shading them out and as it has no natural predators in this country is able to completely dominate the habitats where it grows. Pulling it up is very easy and quite satisfying as you feel its roots lift away from the ground. It is important when pulling to remove the whole plant as it can resprout from a small section left in the ground.


On the Monday we were joined by 11 volunteers who helped to tackle Skunk Cabbage which is invading the wet woodlands on the headwaters of the river Arun near Haslemere. Skunk Cabbage is still sold in garden centres and quite a popular garden plant. The issue is that it escapes easily into watercourses and once established will dominate the wet woodland floor, shading out all other species. The National Trust joined us in this task and we will be returning the favour in early August by helping to clear their section of the stream (all our welcome to come along). We hope between us to clear this entire upper tributary returning the area to our native species. Forming partnerships like this between different organisations and groups is a very effective way to get on top of the problem.


On the Tuesday we held an invasive species identification workshop at Merrist Wood Agricultural College just round the corner from our HQ. Attendees got the chance to see invasive species up close in the classroom before having a walk around the college campus to see them up close in the wild. We were lucky enough to find a signal crayfish in the stream on the way round much to everyone’s delight.


Wednesday to Friday again were Himalayan balsam bashing tasks at Fox Corner, Farnham Park and Thundry Meadows nature reserve. The Fox Corner task had a particularly large turnout of 22 volunteers who between them managed to clear a whole section of the Hodge brook running into the reserve. The success of the day was particularly thanks to close working with Worplesdon Parish Council and Fox Corner Community Group who helped to advertise the task.


Overall 68 volunteers took part in the week and cleared an enormous amount of Himalayan Balsam and Skunk Cabbage.
We owe a huge thanks to all those who took part and will move forward from here with some great ideas of how we can pull together people in the future to fight the spread of these troublesome species.
 

Glen Skelton

RiverSearch Coordinator

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