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The Celtic rainforest

Rhaeadr Ddu (or ‘the black falls’) deep in the Ceunant Llennyrch gorge Rhaeadr Ddu (or ‘the black falls’) deep in the Ceunant Llennyrch gorge Woodland Trust
12 Jun
In this month’s Discovering Britain trail, Laura Cole explores Coed Felinrhyd, an ancient rainforest hidden in North Wales

For more great walks, trails and viewpoints, be sure to check out the new Discovering Britain Facebook page by clicking here.

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The forest looks like it’s on something – extra fertiliser, steroids, or a mysterious science-fiction chemical? Being tucked away beyond Maentwrog Power Station, a humming 30MW hydropower plant, only adds to this feeling of an experiment gone wrong, or wonderfully right. At Coed Felinrhyd the plants are intense. All around, young ferns uncurl their seahorse-heads from clumps of moss, which have grown so big and fleecy they could almost sprout legs and frolic away. Oak trees hold tight fistfuls of their new leaves – shocks of neon and yellow against the dark backdrop of the gorge. There is rain from above, a stream hissing below, and everything in-between is sopping wet.

‘It is a genuine temperate rainforest,’ says Kylie Mattock, who manages the forest for the Woodland Trust. Forests like this would once have covered the western seaboard of Europe but now are extremely rare habitats on the continent. In the UK, fragments exist on the steep sides of rivers and gorges, away from the pressure of grazing and deforestation. Parts of these woods are so untouched, the hazel and sessile oak are thought to have been growing uninterrupted since the end of the last Ice Age.

‘In this area of Snowdonia, we can expect 200 days of rainfall every year,’ says Mattock. Weather that is ideal for growing. The wood’s topography, meanwhile, keeps it soggy. The gorge of Ceunant Llennyrch is steep and shady, and parts of it rarely experience direct sunlight or frost. ‘For an ecosystem like this,’ she says, ‘a mild climate and humidity is essential.’



The result is a valley so rich it looks alien. Strange plants such as polypody, or the many-footed fern, cover the roots of trees with big, triangular leaves. The Tunbridge filmy fern, on the other hand, has leaves only one cell thick and gives patches of rock a translucent gloss. There are plants growing on plants: lungworts and liverworts, which owe their name to an organ tissue appearance. They were so-named in the 16th century when it was thought they could help the body parts they resembled.

A spectacular lungwort is one of the main sights on this trail. Latched to an old oak tree like a frilly skirt, the rare lichen is a badge of clean air for the valley. It is particularly sensitive to air pollution and sulphur dioxide, the chemical in acid rain. ‘Tree lungwort would once have been much more widespread,’ says Mattock, ‘but has been lost from more built-up areas due to air pollution and the loss of the mature trees where it grows best.’ Though it can be found in the pockets of Scottish woodland, this is one of the few places outside Scotland where it can be seen.

The secret to Coed Felinrhyd’s extra diversity is time. ‘In terms of conditions for lichen growth, it is the lack of disturbance that allows them to grow,’ says Mattock. ‘While much of the woodland has historically been managed, there are stands of trees, particularly hazel, which have probably never been cut.’

This continuity is important for slow-growing and slow-spreading species such as ‘blackberries in custard’ which, with its yellow and crusty appearance, is not as tasty as it sounds. Another type called Thelotrema petractoides or barnacle lichen was discovered here in 2015. Because it takes so long to establish itself, its presence provides further proof that the forest has been here for millennia. ‘Barnacle lichen would have slowly colonised the UK as trees advanced after the last Ice Age,’ Mattock explains. ‘It has survived in this now rather unusual humid habitat with plenty of old, bare-barked hazel but are found nowhere else in Wales.’



The place is not completely devoid of human interference. Walking up the west side of the valley, I am greeted by a single sheep grazing inside the ruins of an old barn. Its boundaries are marked by a few drystone walls which, being totally consumed by moss, look as though they have never been dry.

The barn was probably used for hafod a hendre farming, a Welsh term for the seasonal movement of flocks into the mountains for haf, the Welsh word for summer, and back into the main farm (or hendre) during the winter months. The farming would have been low impact and only lightly grazed, a technique which is still in practice with a small flock of sheep in the Llennyrch woods today.

Other types of farming have had more impact. I am struck by the difference of the forest on the other side of the wall, which abruptly changes to dense Douglas fir and western hemlock. Here the ancient forest was overthrown by a pine plantation seeded in the 1960s. ‘This process was quite damaging,’ says Mattock. ‘Old oaks were felled, vegetation cleared and ranks of shade-casting species planted in the aim of increasing national timber production.’ Rhododendron was introduced and flourished in the acidic soil suppressing other vegetation.

In 1992, the Woodland Trust acquired this area and has been trying to bring back the native oak and hazel. But it is a complex process. ‘We describe woods such as Coed Felinrhyd as a ‘plantation on ancient woodland sites,’ explains Mattock. Unlike farmland or a drained bog, ‘these plantations are places that were woodland consistently for many hundreds – and probably thousands – of years before they were replanted with conifers.’

Simply clearing the conifers would do more harm than good. The forest’s microclimate would become drier and hotter, allowing brambles an opening to take over. Instead, it has to be restored like a building, with the unwanted components taken out while the architecture of an oak ecosystem is reintroduced.

‘Some mature oak trees survived in the plantation, although they soon struggled for light against the wall of conifers,’ explains Mattock. ‘We have gradually “halo-thinned” around these old trees to allow them light in order to thrive once more.’

Meanwhile, Mattock points out, the real work is occurring under the ground: ‘The complex community of native micro-organisms and fungi that have evolved together over those hundreds of years do not disappear overnight. The remnants we see on the surface suggest that the hidden fabric of the ancient woodland, though partially damaged, remains.’

It’s possible to see some of this slow transformation taking place. I pass by a few young oak saplings beginning to grow, breaking up the uniform patterns of the fir pillars. Dead trees are in various stages of decomposition on the forest floor, which wood sorrel, mosses and bilberry are recolonising.

Walking along this borderline between old and new forest, it is clear that it will take decades to change the plantation back to a diverse ecosystem. Coed Felinrhyd and Llennyrch show just how extraordinary Atlantic oaklands can be, so long as they are given enough time.

• Location: Wales
• Type: Rural
• Duration: 1 hour
Click here for more details

Unearth more of our nation’s history and find more great walks, trails and viewpoints around the UK at discoveringbritain.org or via the new Discovering Britain Facebook page.

This was published in the June 2017 edition of Geographical magazine.

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