Punting along the River Cam may soon become a thing of the past if growth of an invasive water plant continues unchecked in the river, authorities have warned.

Pennywort, a floating water weed that originated in North America, grows in mats across the surface of the river, making the waters difficult to navigate. The growth of the weed also threatens other life in the river, such as plants, fish, and insects, by blocking out sunlight and oxygen.

Dr Philippa Noon, River Manager with the Conservators of the Cam, described the weed as “unlike any other native plant, with the leaves being bright green, rather like oversized coriander.” She added that the “weed itself is harmless and...makes good cattle fodder.”

However, authorities are concerned that, rather than posing an environmental risk, the weed may obstruct punts and boats on the river. According to a spokesman for the Department of Rural Affairs, “If the problem takes hold around Cambridge the iconic and traditional pastime of punting may have to be stopped due to the health and safety risk of a punting pole or boat getting tangled in floating pennywort.”

The prospect of Cambridge’s favourite water sport being threatened has alarmed many students. According to a second-year rower, “The news is really concerning. For many students, punting and rowing are quintessential Cambridge activities, and we should be doing all we can to ensure we can continue doing it.”

Fortunately, the situation around Cambridge is not yet dire. Dr Noon said that “the weed is dormant in the form of little bean-shoots and it probably won’t become obvious to the eye until around July”.

She also pointed out that, “the floods this February/March should have washed some of the weed out of the Cam Conservancy Area towards Upware.”

The weed can be removed from the river relatively easily. The Cam Conservators have been using a specialized weed harvesting boat to “tease” the pennywort mats off the water and lifting them onto riverbanks where they dry out and die.

In addition to mechanical clearance, the Environmental Agency has also been using selective herbicides to kill the weed.

However, if the growth rate reaches high levels, authorities may be forced to target high-priority areas of the river only. High-priority areas include those that are deemed important for sustaining wildlife, or those that are classified as Sites of Special Scientific Interest (SSSI).

In the past, the Cam Conservators and other river authorities have relied upon the work of volunteers, a resource that may be needed to help combat the problem if it takes hold around Cambridge.

According to Dr Noon, “Of course we should welcome any volunteer efforts later in the summer if any of the students are minded to help”.

Interested students can also become involved with the Cam Valley Forum, a local environmental lobby group that aims to raise public awareness about various threats faced by the river, including that of invasive plant species. The Annual General Meeting of the group will take place on Monday March 29th.