🐟 7 alarming things I learned about urban rivers
Hey folks! A local river may look like a place for water, ducks and the occasional shopping trolley, but then river expert Lawrence Beale Collins explained what else travels through the Ravensbourne catchment: invasive plants, heavy metals, sewage, dumped party toilets and unwanted pets.
Invasive plants use rivers as transport systems. Himalayan balsam, giant hogweed and Japanese knotweed love damp places and riverbanks. The river does the delivery work: seeds and plant fragments move through the catchment and settle on the banks.
Giant hogweed is basically a Victorian garden souvenir with chemical warfare capabilities. Giant hogweed came from the Caucasus region, helped along by Victorian plant hunters “doing their good work”, as Lawrence put it. It is highly toxic: brush it with your skin, and you can get rashes or blisters.
Japanese knotweed smells lovely, but it tries to invade your house through the floor. Japanese knotweed is very pretty and, when it flowers, smells fantastic. Unfortunately, it can exploit cracks and weaknesses in concrete, tarmac and asphalt, which is less charming.
Urban rivers can look healthy while hiding serious pollution. The Ravensbourne catchment in south-east London can look beautiful, but, according to Lawrence, nature has “a very good way of disguising” what is going on, from construction runoff to road pollution, sewage overflows and all the other gifts humans keep sending downstream.
Terrapins became a river problem because people released unwanted pets. The terrapins in London rivers are probably there because children were bought turtles after the Ninja Turtles craze. Then the turtles grew, became “quite chunky”, and were released into local rivers and lakes, where they now eat anything in the water, including fish eggs and ducklings.
A dumped portaloo once killed a lot of fish. In 2021, someone having a birthday party in a park hired a portable toilet and dumped the contents down a drain, apparently to avoid disposal costs. The ammonia entered the river system, killing 2,000 fish.
Dog flea treatments can wash into rivers when dogs swim. At Beckenham Place Park, dogs go into the river all the time. Some carry flea treatments that can wash into the water, adding chemicals known to harm aquatic life.
Friends of Brookmill Park organised Lawrence’s lecture. You can follow him on Instagram, and check out our website for more events like this.
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Elia Kabanov is a science writer covering the past, present and future of technology (@metkere).
Cover art: Elia Kabanov feat. DALL-E.