Foreign Invasion: The Destructive Habits of Introduced Species

Foreign Invasion: The Destructive Habits of Introduced Species
Published: Dec 10, 2012
Liam Desroy examines the impact introduced species are having on Britain's wildlife.



I’m in a cafe in the Nant Gwynedd valley of north Wales, talking to a burly guy in workman’s overalls and heavy boots. He has a manner of inhaling deeply whenever I speak which causes his chest to rise up and swell. I’m in constant fear that I’ve somehow offended him and that he is about to break my neck. His name is Fluff. Only really hard men are called Fluff.


Our conversation is a strange one; he’s telling me how the problem has gotten out of hand and that “too many of them” are making their home in northern Wales and driving off the natives. That the influx is out of control and the only option left is to kill them. That this is his job.


Other customers are giving us odd looks.


They can rest at ease, however, as we’re not discussing far-right activism over cream teas. Fluff is actually part of a council-funded team responsible for the removal of rhododendrons from the Welsh landscape – and, in particular, preventing them from encroaching on power-lines. It’s a seemingly simple project, but not so, because every time the crew removes a single plant, several others spring up in its place. It seems this foreign invader is making short work of conquering the British countryside. 


Rhododendrons were first brought to Britain from the Himalayas by the Victorians, who were drawn to the striking colours and thick canvases that proved useful in shading streets during the summer months. 


Since then they have steadily taken over the British countryside. The plant is characterised by a particularly ruthless growth pattern; its aptitude for blocking sunlight kills off any plant unlucky enough to get beneath its covering.


The rhododendron also has the capacity to cover large areas of ground very quickly with two methods of expansion. As well as spreading through seed dispersal, rhododendrons have branches that are capable of sprouting roots if they come into close proximity with soil, allowing plants to grow laterally as well as vertically. A single plant can cover up to 100 square metres and grow up to ten metres high, smothering vast areas in complex labyrinths of tangle. Fluff’s description of the plant’s growth patterns brings to mind sci-fi horrors from the 1980s.




These aggressive patterns of expansion have made the rhododendron a common sight throughout Wales, England and Scotland. You only have to take a look up Nant Gwynedd to see proof; every inch of the valley is blanketed in the stuff and the only other plants remaining are the smattering of lone trees that rise high enough to escape the tide. In spring, when the flowers bloom, it’s actually quite a beautiful sight, as the area becomes awash in a sea of colour. The plant is seen by some as boost to the local economy, with tourists travelling to see the purple hills and buying their own rhododendrons to take home from local garden centres.


But this small upside is unlikely to change the mind of ecologists as the plant is proven to contain a substance that is toxic to most animals. “Rhododendron areas are essentially barren,” says Countryside Info. Rarely is a creature found around the plant or on its surface. Countless species, such as the dormouse, are being driven to near extinction due to the Himalayan plant. Even honey made from the pollen is a mild poison. “It suffocates habitats and hampers biodiversity,” says the Commission's Native Woodland Ecologist, Richard Thompson. “Getting rid of it would be a real shot in the arm.”


This toxicity has made grazing useless as a method of control as animals only seem to ingest the leaves when there is no other alternative, and, when they do, they frequently become sick and die. According to Fluff, one of the few effective methods of dealing with the plants is to burn through the waxy leaves with herbicides which, bearing in mind the vast stretches of rhododendron trees, means a whole lot of chemicals.


Efforts all around the UK are being made to keep the plant at bay. The Forestry Commission Scotland implemented a fifteen-year plan to remove the plant in Cowal & Trossachs, Lochaber, West Argyll, North Highland and Galloway but an estimated £15m will be needed if the project is to be a success. It looks set to take groups, such as Fluff’s, decades to gain control of the situation. His description of the plants as “that relentless army” is by no means an exaggeration.


I finish my coffee and jump into the car, travelling up a tight road that bends up the back of Snowdon. Every side is steeped with a uniform of rhododendron monotony leaning across rivers and spilling over dry stone walls. My encounter with Fluff has set me on edge. I keep glancing nervously at the rhododendrons lining the road, as every corner I take seems to reveal a new expansion to their empire. I think of Fluff and his small crew back in the hills, surrounded by the forest, hacking away at the growing mass. I put my foot down and leave the area behind.


Good luck boys.











The rhododendron invasion is by no means the only such case to wreak havoc in the UK. Here are few others species who found a new home on British land.


Signal Crayfish

In the 1970s, the signal crayfish was brought over from the US to replenish the failing numbers of the native crayfish, the species suffering from a disease known as ‘crayfish plague’. However, due to an unfortunate oversight, this only worsened the situation: the signal crayfish was also a carrier of the disease. The plague destroyed most of the native crayfish population and the few that remain are being killed off by their bigger, foreign cousins.


The Grey Squirrel

Introduced during the 19th century, the grey squirrel has managed to scramble its way onto the International Union for Conservation of Nature’s list of 100 worst invasive species. It has driven the native red squirrel to near extinction and had a negative impact on local flora and woodland birds.  


Red Necked Wallaby

Although an unintentional introduction, the red neck wallaby made a low key settling onto our shores in the 1940s after being emptied out of a zoo in WWII. It is only marsupial on record in the UK and despite popularity as an oddity and a surprising hardiness to the weather, the survival of the animal looks unlikely and some already think it to be extinct.


The Red Kite

And finally, a success story: at the start of the 20th century, red kite numbers had dwindled to just a handful of pairs in the U.K but after numerous reintroductions, the population is thriving. Now a frequent sight throughout England, Wales and Scotland, the red kite is heralded as one of the few success’s in human intervention.



Photos by Tom Medwell



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