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6 Nov 2018

Extreme invasive species extraction

A view of Corrieshalloch Gorge on a sunny day, showing the waterfall tumbling down the steep-sided gorge.
We’re rooting out invasive species at Corrieshalloch Gorge NNR.

We’re going to extreme lengths to protect one of Scotland’s most spectacular gorges from the effects of invasive plant species – including abseiling and enlisting the help of ‘gorge scramblers’ to root out the problem.

Work has begun at Corrieshalloch Gorge in Wester Ross to remove Rhododendron ponticum and Japanese knotweed, which have spread in the ravine and downstream along the River Broom.

Conservation workers abseiled into the gorge to identify spots where the species have grown and – depending on the size of the plants – inject, weed-wipe or spray them with measured doses of herbicide.

Two men in waterproof hi-vis clothing and helmets abseil down a steep side of a gorge. They are surrounded by tree branches.
Conservation experts abseiled into the gorge to remove invasive species.

Both species are notorious for reducing biodiversity, causing the loss of local flora and fauna. Rhododendrons block out sunlight and prevent other plants from growing, while Japanese knotweed can loosen river banks with its aggressive root systems.

The move will protect Corrieshalloch Gorge’s diverse range of native trees – including aspen, hazel, rowan, birch, pine and wych elm – and its rich assemblage of mosses, lichens and ferns. The gorge is also home to a variety of wildlife which depends on its flora, such as red squirrels, woodland birds, ravens and golden eagles.

“These plants are in a very extreme place to access, but we need to take thorough measures to make sure we identify the areas affected and remove the invasive species.”
Rob Dewar, Nature Conservation Advisor (North)

In addition, the Trust is being helped by Scotland’s ‘gorge scrambling’ community – regular visitors to Corrieshalloch. The pastime involves people making their way up or down a mountain river course, jumping into pools and swimming under waterfalls to experience nature in a different and more personal way.

In the pursuit of their hobby, gorge scramblers get into areas that might not otherwise be accessed by regular surveys – they may spot colonies affected by the invasive species that no one else would.

Four people walk along the bottom of a gorge towards a waterfall. The large slabs of rock are glistening, and the river rushes past on their right.
Gorge scramblers at Corrieshalloch help spot invasive species.

Rob Dewar added: ‘The gorge scrambling community is acting as our eyes in the difficult depths and corners of Corrieshalloch – we’re also working with them to develop sustainable adventure tourism at the site. We want to use their knowledge as much as we can to tackle colonies of the invasive plant species that may otherwise be missed – they can make a real difference to the future of the gorge, all while doing what they love.

‘The control of Japanese knotweed and rhododendrons is part of a larger project with other landowners to protect biodiversity on this river catchment. The work at Corrieshalloch is a great example of the extreme lengths to which we will go to protect Scotland’s natural heritage, preserving our history and culture for current and future generations to enjoy.’

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