As summer issues its last hurrah, working parties around the country have been busy removing Himalayan Balsam from our riverbanks. Lucy Wood reports…
The non-native species is damaging to the environment and illegal to spread under UK law, and every summer teams of hardy volunteers gather to fight the perpetual threat.
In Lincolnshire, the East Mercia Rivers Trust (EMRT) has been clearing balsam from the banks of the River Bain, in Horncastle. It said: “Himalayan Balsam might look beautiful, but it causes serious problems. It outcompetes native plants, threatening biodiversity, destabilises riverbanks by increasing erosion and flood risk and disrupts pollinator patterns, dominating nectar sources. It dies back in winter, leaving bare soil that washes into rivers, harming water quality, especially in our rare chalk streams here in Lincolnshire.
“Under the Wildlife and Countryside Act 1981, it is an offence to plant or cause Himalayan Balsam to grow in the wild. That means we all have a role to play in helping to control and remove it. At East Mercia Rivers Trust, we are tackling this invasive species through our Horncastle Riverscape Enhancement Project, and people are invited to join our volunteer work parties. Make a difference and help protect your local environment!”
Other groups around the country have joined the balsam bashing army, including the Pocklington Canal Amenity Society, Eden Rivers Trust, the Canal & River Trust’s Adlington Taskforce, West Cumbria Rivers Trust, Lancashire Wildlife Trust, the South East Wales Rivers Trust community litter-picking groups and many more local organisations.
Also in Lincolnshire, volunteers at RiverCare Grantham, part of the wider RiverCare & BeachCare organisation, have too been tackling the immense challenge of keeping balsam at bay on their adopted stretch of the River Witham.
“Summer means more than just litter picks. Since late May, we’ve been deep into Himalayan Balsam surveys and ‘bashing’ – a critical fight to protect our rivers,” said the group.
“Years of effort at Queen Elizabeth Park and the National Trust’s Belton Estate have seen a significant drop in balsam populations, making control more manageable. This year we have expanded our reach from Harrowby Weir to the Belton Estate, successfully engaging with four landowners for surveys and pulling efforts – a great start! One recent session alone involved five hours of dedicated bashing.”
In County Durham, the Wear Rivers Trust encountered two-metre tall balsam at a recent clearing session, when Durham Wildlife Trust joined volunteers. It was held as part of the Links With Nature project, designed to connect people and nature in the area. The £2.2 million initiative began in May thanks to funding from the National Lottery Heritage Fund and Sunderland City County, the North East Community Forest and Northumbrian Water’s Bluespaces programme.
Floating pennywort is another invasive species originally introduced by the aquatic nursery trade as a plant for use in ornamental ponds that grows into large floating mats of dense foliage by up to 20cm a day, smothering our waterways. Similar to balsam, in the UK it is illegal to cause it to grow in the wild, and it has been banned from sale.
The Canal & River Trust ran the ecology award-winning Invasive Species Eradication Project, which ended this year, focusing on tackling four priority invasive plants that are damaging canals, destroying habitats and harming wildlife. It was the largest invasive species eradication project on UK inland waterways.
“Invasive non-native species are one of the largest global threats to biodiversity, and our canals and rivers,” said the trust. “Japanese knotweed, giant hogweed, floating pennywort and water fern (Azolla) can grow at rapid speed, often from the most minuscule of fragments. This makes them costly and challenging to remove completely. Without regular and effective management, their dominating presence could cause irreversible damage to the fragile ecosystems of our waterways. This four-year project enabled us to trial ground-breaking methods of eradication to find more sustainable, cost-effective and longer-lasting solutions.
“Throughout the four years, we were able to attempt first-of-a-kind trials, including an eco-friendly dredging, hessian matting and hydroseeding process on Himalayan balsam found at the Penarth Feeder, which reduced the need for further treatment by 90%.
“After many years of research, we were able to use weevils to help eradicate floating pennywort and water fern. These plant-munchers effectively reduced vast quantities in a matter of weeks, offering a natural alternative to chemical sprays. Vital research conducted on the impacts of water and sediment quality on the presence of algae and invasive macrophytes (aquatic plants) will also enable us to shape future biocontrol strategies effectively.
“Other areas of success included the eradication of invasive plant species from 313km of waterway, aquatic weed management via mechanical removal across 108km of waterways, targeted treatment in more than 300 land-based invasive species sites, successful one-of-a-kind trials of Himalayan Balsam in two sites and one of, if not the, largest floating pennywort removal exercises, resulting in 1500 tonnes removed across 35km.”
Although the project has ended, the trust said its work to tackle invasive species is not over.
“The team will participate in National Floating Pennywort strategy groups to build on our successes and identify additional opportunities to tackle this particular plant,” it added.
“With a largely successful weevil release, we will also continue this eradication method in all regions and monitor the progress. It is evident that climatic factors such as air and water temperature have a significant impact on the successful overwintering and feeding activity of the weevils, and this must be a key consideration on both invasive plant growth and the biocontrol methods that are used to eradicate them.”
