Legging through

British Waterways "Dirty Dozen"

The twelve most unwelcome pests in and around Britain's waterways!

(Pictures and words courtesy of British Waterways)


1. Japanese Knotweed

One of the most invasive weeds in Britain, its dense growth crowds out native vegetation, erodes riverbanks and causes structural damage. Growing up to 3m high, this horror is common throughout Britain and can regenerate from tiny fragments.

2. Floating Pennywort

This fleshy-stemmed plant uses its roots to interweave a floating mat of lush foliage. But don’t be fooled by this former resident of tropical aquaria and garden ponds, this pestilential plant is a real problem – it grows very rapidly in late summer and is responsible for choking waterways, crowding out native plants and taking oxygen from fish and insects.

3. Giant Hogweed

This former ‘beauty queen’ of 19 th century ornamental gardens, now found along waterways and areas of wasteland, grows up to 5m high. This dangerous, dark green giant produces thousands of seeds and can shade out other plants, increasing the risk of bank erosion. It also contains sap that can burn the skin when exposed to sunshine.

4. Australian Swamp Stonecrop

Sold in garden centres as an ‘oxygenating plant’, rapidly growing Stonecrop can quickly smother native vegetation. Spreading across the country since the 1970s, this yellow and green stemmed nasty can re-grow from tiny fragments and lives in a variety of habitats.

5. Water fern

The popular pond plant is also known as Fairy Fern but there’s nothing ethereal about this floating fiend, which forms dense mats of vegetation on the waters’ surface that may pose a hazard by appearing solid. Able to withstand British winters and invade a region very rapidly, this innocently sounding plant can reduce light beneath the surface, killing native plants and causing de-oxygenation.

6. American Signal Crayfish

Found throughout England, these brash 15cm-long beasts are aggressive, breed faster than the native species and damage banks with their burrowing. These filthy thugs also carry a fungal disease - ‘crayfish plague’, which is harmful to our native species.

7. Himalayan Balsam

Despite its soothing name, this densely growing pink and red-stemmed brute has an anti-social habit of projecting its seeds up to four metres away, allowing it to stifle native grasses and plants in its path. It dies back in Autumn but its destructive legacy lives on as it leaves waterway banks vulnerable to erosion.

8. American Mink

The bully of the inland waterway, mink are often mistaken for otters but are smaller and far more aggressive. An efficient predator, this menace - brought to Britain in 1929 for commercial fur farms – has a score to settle and will greedily dine on a variety of waterway natives, including fish, birds, invertebrates and Wind in the Willows’ favourite, the water vole.

9. Zebra Mussel

These stripey stowaways landed in Britain’s waterways on the hulls of ships from Eastern Europe and decided to stay. Growing up to 5cm long, the nautical nuisances reproduce rapidly and form large colonies that attach to almost any submerged hard surface, impeding the smooth running of canal gates and sluices.

10. Zander

This wide-mouthed predator has excellent vision and fang-like teeth, which it uses to eat native fish and steal their food. Highly adaptable, this voracious carnivore has now spread and thrives in large, slow flowing waters in Central England.

11. Chinese Mitten Crab

Named after their white tipped claws, these 8cm-long Asian crustaceans have a voracious appetite for almost anything that gets in their way. Their extensive burrowing damages canals, drainage embankments and structures – mostly in London, where they were found more than 70 years ago.

12. Red-eared Terrapin

Britain’s inland waterways were a safer place for bird eggs and insect larvae before these terrors came along. Brought to Britain from the USA as pets, these real life ‘Ninja turtles’, which can live for 25 years, are often dumped in the wild when they grow too big or their owner gets bored.

 

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