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14 Dec 2022

Lichen at Corrieshalloch Gorge NNR

Written by Bruce Macdonald, Ranger
A close-up photo of some grey, green and pink lichen, with some sections shaped like little funnels or cups.
Pixie cup lichen
The consistently damp, shady and undisturbed conditions of the gorge create the perfect habitat for a host of mosses, lichens, liverworts and ferns. In fact, past surveys of the site have catalogued nearly 300 species of lichen alone.

The awe-inspiring Corrieshalloch Gorge is one of the most dramatic examples of this geological feature in Britain. It was fashioned by meltwater from a large glacier, which once occupied the Loch Broom valley. The bedrock that underlies much of the area is a blend of metamorphosed mudstone and sandstone, known as the Moine. At Corrieshalloch, tectonic movement created a fine-grained type of rock called mylonite, which contains faults and splits easily. These faults allowed torrents of meltwater to shear away chunks of material, carving out the narrow chasm we see today.

A view looking along a deep, woodland gorge towards a waterfall. A suspension bridge spans the gorge above the waterfall.
Corrieshalloch Gorge NNR in Wester Ross

The diverse woodland flanking Corrieshalloch Gorge is a fine example of Scotland’s temperate rainforest, exhibiting many attributes associated with this rare and internationally significant habitat. Scotland’s rainforest is situated on the west coast, where rainfall is high and temperatures mild due to the influence of the Gulf Stream. Other hallmarks of temperate rainforest include varied topography and diverse woodland, housing a range of native species of all ages. The woodland at Corrieshalloch is carefully managed to encourage lichen and other plants to thrive. For example, by thinning dense areas of woodland, more light can reach the forest floor – giving wildflowers, ferns and smaller trees the chance to develop and creating a rich understorey.

“Lichens are important because they provide clues about the health and quality of our habitats.”
Bruce Macdonald
Ranger at Corrieshalloch Gorge NNR

Most lichens are sensitive to pollution, so their presence can be a sign of good air quality. They are also valuable to wildlife, providing food and shelter for many invertebrates and nesting material for birds. Preferring largely undisturbed habitat, some lichen colonies can be indicators of ancient woodland.

Lichen is not a single organism; it is a mutually beneficial relationship between a fungus and algae (symbiosis). The fungus forms the body of the lichen (thallus), providing protection from the elements; the alga creates food from the sun’s energy (photosynthesis). In most lichens, this photosynthetic partner is green alga, but some contain cyanobacteria (blue-green alga).

When you visit Corrieshalloch Gorge, you don’t have to go far to be met with a rich display of biodiversity. Lichens decorate trees, stumps and rocks along the paths, with several species often crammed into one small area. From the lofty heights of Sir John Fowler’s impressive Victorian suspension bridge (built in 1874), lichens can also be seen plastering the sides of the gorge like a natural render.

The lush abundance of species found in Scotland’s rainforest makes this habitat of international importance. Like many of the species it hosts, temperate rainforest is rare, covering less than 1% of the planet. Despite representing a tiny portion of Scotland’s woodland cover, our rainforests are some of the best remaining examples in Europe, requiring careful long-term management to avoid the decline of this unique habitat. Some threats to Scotland’s rainforest include overgrazing, invasive non-native species, exotic conifer plantations, pests and diseases, as well as climate change and pollution.

At Corrieshalloch, there has been significant work to remove Rhododendron ponticum and other invasive species, such as Japanese knotweed. Rhododendron shades out other plants and lichens, while the burrowing root system of Japanese knotweed can loosen the sides of the gorge.

Two men in waterproof hi-vis clothing and helmets abseil down a steep side of a gorge. They are surrounded by tree branches.
Specialist rope workers access the sides of the gorge.

Corrieshalloch Gorge was designated a National Nature Reserve (NNR) in 1967 in recognition of its breathtaking beauty. It is also a Site of Special Scientific Interest (SSSI) for its native woodland, home to nationally and internationally important species.

Since February 2022, work has been taking place at the gorge to improve the experience for the thousands of visitors we welcome there every year. The project will improve facilities and develop a gateway to nature at the National Nature Reserve, one of eight in the Trust’s care.

So far, access has been improved with a new 800m path, created to allow people to see the gorge from a different perspective. A new welcome centre – which includes toilets, a takeaway café and blue and grey waste provision for motorhomes – is now nearly complete. The new centre will remove pressures on parking in the area by accommodating 22 cars, 4 motorhomes or minibuses, 6 motorcycles and 2 coaches, as well as providing 2 electric points and 2 disabled and parent-and-child parking bays. The existing car park will also be resurfaced and extended to accommodate more vehicles.

The facilities are due to open in spring 2023.

The £2.3 million project has secured £923,277 funding from the Natural and Cultural Heritage Fund, which is led by NatureScot and funded through the European Regional Development Fund. It is part of an almost £9 million Scottish programme of projects to invest in the Highlands and Islands, to provide more and better-quality opportunities for visitors to enjoy natural and cultural heritage assets.

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