Fresh insight into invasive plant that blights UK rivers

August 10, 2018, University of Stirling
Himalayan balsam. Credit: Nigel Willby

New research into the behaviour of an invasive plant seen on riverbanks across the UK could help improve the management of the problem, experts have found.

The University of Stirling study provides clues as to why the abundance of Himalayan balsam—which has an adverse impact on native plants and river habitats—varies dramatically from place to place.

The work could help mitigate the impact of the pink-flowered plant, which outcompetes native species, causes shading and reduces the stability of riverbanks, enabling silt to enter the water.

Dr. Zarah Pattison, of the Faculty of Natural Sciences, led the research, published in Ecosystems.

She said: "Our research has found that Himalayan balsam dislikes overly moist conditions, unlike the native plants—such as nettles, butterbur and canary grass—which dominate our lowland riverbanks. It prefers drier, steeper riverbanks where it can compete more effectively with the native .

"This knowledge offers a gateway to managing Himalayan balsam indirectly, by manipulating conditions on riverbanks."

River engineering often involves straightening and over-deepening rivers and, combined with the abstraction of water, this leads to drier riverbanks during the summer, benefitting Himalayan balsam growth. This effect of riverbank drying may also be exacerbated with future climate change and drought conditions, as seen this summer across the UK.

Himalayan balsam. Credit: Nigel Willby

In contrast, the restoration of rivers often results in gently sloped banks, meaning water is retained and riverbanks are therefore moister, favouring native species.

The authors also found that riverbanks with a large abundance of are more likely to resist invasion by Himalayan balsam.

Dr. Pattison believes the findings will aid river management by helping to pinpoint resources in attempt to control Himalayan balsam.

"The UK spends an estimated £1.7 million on managing invasive alien species, including thousands of man-hours manually removing or spraying species such as Himalayan balsam," she said.

"Therefore, understanding the conditions which benefit the growth and spread of this species will enable better management and use of resources, in order to control the amount and spread of Himalayan balsam."

The research involved field surveys conducted along 20 rivers across the Central Belt of Scotland.

The team used a technique, structural equation modelling, to assess the data and understand the effects of the environment and resident plant community on the abundance of Himalayan balsam.

Explore further: Clever enemy could control invasive plant pest

More information: Zarah Pattison et al. Riverbanks as Battlegrounds: Why Does the Abundance of Native and Invasive Plants Vary?, Ecosystems (2018). DOI: 10.1007/s10021-018-0288-3

Related Stories

River areas overrun by invasive plants

August 2, 2017

Rivers are high-speed corridors for the spread of invasive exotic plants. Increasingly, these plants are pushing out native species and making floods more likely. A study conducted by Deltares, Utrecht University, Radboud ...

Scientist urges us to 'embrace new invaders'

October 4, 2013

A University of York scientist claims that invasive species such as Himalayan balsam and rhododendron should be welcomed to Britain rather than reviled. At least, they should not be hated simply because they are alien, he ...

Exotic invasions can drive native species extinct

June 19, 2018

Latest research from the University of Southampton has revealed the impact of exotic species upon native wildlife, which could potentially lead to native plant species extinctions within their natural habitats.

Plant roots shaped by river fluctuations

November 18, 2015

Changing flow rates in rivers can be disruptive to bushes and trees that grow on riverbanks. Now, researchers from EPFL have developed a way to predict how fluctuations in the water table impact the roots that nourish them.

Recommended for you

Researchers come face to face with huge great white shark

January 18, 2019

Two shark researchers who came face to face with what could be one of the largest great whites ever recorded are using their encounter as an opportunity to push for legislation that would protect sharks in Hawaii.

Why do Hydra end up with just a single head?

January 18, 2019

Often considered immortal, the freshwater Hydra can regenerate any part of its body, a trait discovered by the Geneva naturalist Abraham Trembley nearly 300 years ago. Any fragment of its body containing a few thousands cells ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.