Over one-fifth of the Laune River is affected by Japanese knotweed.
According to Jane Jackson of the Save Our Laune group, there are a large number of invasive species spreading rapidly along the 22km river.
The invasive species, such as Himalayan balsam and Japanese knotweed, cover many of the indigenous plants, which has an effect on the pollination of plants and flowers.
Erosion of the river bank also takes place due to the shallow roots of the invasive species, leading to flooding and lessening of fish stocks.
The Save Our Laune group are holding an event on Saturday, August 20th, to raise awareness of the threats facing the river and its tributaries.
Jane Jackson says it is not just Japanese knotweed that is causing a problem.