The canal running beneath the world-famous Black Sabbath Bridge is turning green, thanks to the arrival of an invasive water plant on Westside.
At night, the water beneath the famous Black Sabbath Bench can look like a solid green felt carpet that could be tempting for unsuspecting dogs to try to walk on.
By day, the duckweed sinks to just below the surface when it is broken up by narrowboats or by visible heavy rain.
Our video captures the duckweed at night, by day in the warm and even during a storm. Watch our video here:
The duckweed seems remarkably resilient under different conditions and looks to have been thriving under most of them. It can be beneficial to the ecosystem in modest quantities. But if left unchecked in areas of still water, the Canal & River Trust says it can spread from 10 sq cm to a hectare (which is 100 million sq cm) in less than seven weeks.
Apart from the steady narrowboat traffic helping to limit its impact in Westside, there is one other factor that will limit its ambitions to take over the canals – and that’s a cold winter.
A Canal & River Trust spokesperson told Westside World: “This is the first time we have duckweed on the canal in central Birmingham. It’s a problematic little weed in that it grows as quick as you can remove it from the canal.
“Warm weather conditions have been the perfect growing weather for it, and it can double in size in a matter of days. The only way to remove it is to scoop it out and dispose of it. When the weather gets cold it will naturally die off.
“The weed itself isn’t harmful and ducks tend to eat on it, but if it gets too thick it can cause oxygen problems in the water for fish. The other issue is that it does trap litter and dogs – and people do sometimes confuse it for grass.”
The Birmingham Canal Navigations (BCN) system has 100 miles of canals. Different weeds are impacting on other parts of the wider canal system.
The spokesperson added: “We’ve also had a problem on the Dudley Canals. This is a different weed called Azolla or floating water fern.
“Again, it’s fast growing and blanket covers the canal. To combat this the best method is to introduce North American Weevils. These little beetles munch through the weed and clear it up for us then sadly die.
“Both these weeds are non-native invasive plants that have ended up in the canal and costs us thousands of pounds each year to clear.
“Most of these plants are mainly transported around our canal by boaters so it is a losing battle trying to stop them appearing. We try to tackle the weeds as soon as they appear so we can stay on top of the problem.”
The Canal & River Trust is the UK’s largest waterway charity, looking after 2,000 miles of canals and rivers across England and Wales. Its mission is to maintain rivers and the 250-year-old canal network in healthy conditions for future generations to enjoy.
The charity currently has 29,000 friends and donors, 14,000 volunteers and 34,000 boaters. Visit this page for more details about the Canal & River Trust’s conservation work.