Exploring the Celtic Rainforest

Ben DolphinA bit of rebranding works wonders for the underappreciated. Back in my bagging days the idea of spending more than an hour roaming a squelchy woodland would have been a complete anathema to me. Not that I didn’t appreciate woodland or forest at the time, mind. I always enjoyed passing through them but they were for just that – thoroughfares on my way to a Munro rather than being destinations in themselves. Times have clearly changed, because a couple of months ago I deliberately spent six soggy but wonderful hours exploring the exceedingly mossy interior of Ariundle National Nature Reserve, a tiny fragment of what is now commonly termed the ‘Celtic Rainforest.’

The unassuming entrance to Ariundle NNR.

‘Celtic Rainforest’ is a loose term used to describe the lush, green and mostly deciduous woodlands scattered along the Atlantic coasts of the British Isles. And as the name suggests, their strongholds are mostly found in the Celtic nations. Each of these ‘Atlantic woodlands’ might be dominated by any number of different tree species such as oak, birch and hazel, but in an ecological sense they are part of a broader habitat type found on the wetter edges of land masses all over the world. From the redwoods of the Pacific Northwest to the beech and laurel of Chile and Japan, from the podocarp and tree palms of New Zealand to the birch and spruce of Norway, this is the ‘temperate rainforest’. Temperate means mild, so there aren’t the extremes of rainfall or humidity that you’re likely to find in the tropical rainforest, but as you can see from the second word that doesn’t mean you won’t need your raincoat.

What makes a temperate rainforest?

1. High rainfall – Scotland often feels uniformly wet from coast to coast so you could be forgiven for asking why this type of forest is confined to the Atlantic side? Well, the difference between our west and east coasts is stark. Our prevailing winds come off the Atlantic, which means the west coast is where the majority of our weather hits first and where most rain is dumped. By the time the weather crosses the hills and reaches the east there is little or no precipitation left to drop. The west coast therefore has, according to the 1981-2010 average, between 1500mm (4.9ft) and 3000mm (9.8ft) of rainfall per year, whereas the east coast has between 600mm (2ft) and 1000mm (3.3ft).

2. Number of wet days – High rainfall isn’t enough in itself. Temperate rainforests wouldn’t have their unique appearance if all that rain fell in only a dozen or so massive deluges, or in only the winter months. The ecosystem needs more consistency than that, and so rainfall needs to be spread evenly across the year with significantly more rainy days than not. Rainy days on the west coast average between 240 and 260 per year, whereas the east coast is more like 170 to 200 days. Quite a difference!

3. No extremes of temperature – Temperatures need to be fairly stable all year round, without the kinds of extremes found inland. The close proximity to a relatively warm ocean means the coastal strip never gets as cold as it does inland, but nor does it get as hot. Naturally there are wide fluctuations in temperature at the coast throughout the course of the year, but they are nowhere near as extreme as inland.

Mild in winter, cool in summer, this stability combines with the drizzle, humidity and the clean pollution-free air brought in from the open ocean to create the perfect conditions for the Celtic rainforest.

The green blanket

The diversity of life really isn’t apparent when you stand in the middle of Ariundle on a cold, wet, autumn day with the rain running down your face, dripping off your nose and pooling in your shoes. On days like that it can be hard to see anything other than bare trees and moss, and impossible to hear anything other than the patter of rain on leaves and puddles. And yet this woodland (and others like it) is an incredibly ‘biodiverse’ place. Oak trees alone are home to a greater variety and number of insects than any other tree in Scotland, including rare beetles and up to 200 different species of moth. Ariundle is also home to nationally rare species like the chequered skipper butterfly and northern emerald dragonfly, and many of the Atlantic woodlands in Scotland are a refuge for otters, bats, wildcat and pine marten.

Look under a branch and every square inch of space is occupied.

For me though, the most remarkable diversity of life in the Atlantic woodlands is revealed when you simply peer below a thick oak branch and look at the array of weirdness on its underside. It’s not a world you recognise. Yes, there are a few small ferns to keep things familiar but the rest is all a bit alien. Leaf-like structures looking somewhat like cabbage (a lichen called lungwort) cover the branches and are peppered with small red blobs. Another crusty orange lichen lines the bark, and pretty much everywhere else are all manner of tiny soft green mosses.

The Celtic rainforest is the domain of the ‘lower’ plants – the lichens and bryophytes. You might not have encountered that second name before, but bryophytes are a group of plants that include mosses, liverworts and hornworts, none of which produce flowers or seeds, nor do they have conventional roots and therefore need to absorb most of their water and nutrients through their surfaces.

Seen together in a single habitat you’re likely to just dismiss all three as moss, as they are all green and short. And because none of them need soil, they end up coating pretty much every single surface available such as logs and boulders. Together with the various lichens higher up in the branches, the whole woodland feels like it’s dripping with life.

Scotland is a hotspot for these lower plants, and its Atlantic woodlands are of both European and global significance. Aided by a diverse variety of rock types and a characteristically knobbly landscape that offers plenty of nooks and crannies for different organisms to thrive on, Scotland has just under 1000 species of bryophytes and around 1500 species of lichen. In tiny Ariundle alone, packed into just 70 hectares are 133 species of bryophytes and 207 lichens – both significant proportions of the Scottish total.

It is little wonder, therefore, that the first thing that strikes you when you first walk through somewhere like Ariundle is just how vividly green (and damp) the place is. But this isn’t the familiar green of fields and urban parks, this is an altogether more primeval shade that forms an otherworldly blanket that seems to cover everything. It is the moss equivalent of snow, where there are no sharp edges, and any details on the ground are reduced to vague hints of what lies beneath. Rocks on the ground become pimples in the blanket, and all surfaces are soft, green and spongy.

In the 1950s sci-fi B-movie

At Ariundle the woodland is interspersed with silver birch as well, and when I visited in autumn the dominant green was off-set by that gorgeous purple hue you get from the twigs after the birch leaves have fallen. In some parts of the woodland it’s less like a forest and more like a set from a 1950s sci-fi b movie. Colourful, surreal, even psychedelic. I therefore spent much of my visit just standing still as the rain fell on my head, looking around at every detail and immersing myself in the saturated beauty of it all.


Woodland similar to that at Ariundle would once have wound its way along much more of our coastline, but has since been felled or grazed away. That’s a familiar story inland too of course, but Ariundle is at least part of a network of rainforest remnants totalling 3000ha along the fringes of Loch Sunart. Viewed from anywhere along its 30km length it is a noticeably more wooded landscape than most Scottish sea lochs, and is all the more beautiful and natural in appearance for it. But what’s really intriguing is that the finest examples of our Atlantic woodlands survived not necessarily because of their inaccessibility, but because of their use to us in industry.

It’s tempting to see ancient woodland as pure, pristine, constant and not having been tampered with, but that’s very rarely the case in Scotland. Ariundle’s appearance today, indeed perhaps its very existence, is thanks to its use as a fuel and the sustainable way in which it was managed. You wouldn’t think it now, but Ariundle and the area around Strontian were once alive with smoke and industry. In the 18th and 19th centuries charcoal from the oak trees was burned on site before being transported to power the Bonawe iron furnace on Loch Etive, and the lead mines at Strontian.

The Atlantic woodlands of Knapdale, seen from Taynish NNR.

The woods were protected through planting and coppicing to ensure the supply of oak never ran out, a practice mirrored by another fragment of this Celtic rainforest, the National Nature Reserve at Taynish in Knapdale. As a result, Ariundle in particular has an unnatural dominance of oak for an oak woodland (weird as that sounds), and is now steadily transforming into a woodland with a more natural mix of different broadleaf species.

It’s curious how commercial forces that led to the demise of many of our forests also ensured the survival of others, and I wonder if that could be an uncomfortable truth for some people when they’re wandering through what appears to be, on the surface at least, a timeless, ‘natural’ place.

Rebranding nature

Given the different species composition, scattered locations and diverse histories of these fragmented woodlands, you have to wonder to what extent the term ‘Celtic Rainforest’ could ever be genuinely representative of a greater whole across the British Isles. There are certainly people out there who take a cynical view of the moniker, but wherever the concept came from there’s no denying that it has caught the public’s imagination and has been warmly embraced by conservation charities, government agencies and tourist offices from Cornwall to Coigach.

I assume that was the intention, because like I say a rebranding exercise can work wonders for the rare, the threatened and the underappreciated. Just look at efforts in the last decade to rebrand the Scottish wildcat as the Highland Tiger. So much in conservation these days relies upon ‘interpreting’ the environment for the public, using all kinds of techniques (whether that’s leaflets, info panels, apps or guided walks) to provoke an emotional response, stir their imaginations and get them to think about things that have hitherto been beyond their experience. As the great American pioneer of interpretation, Freeman Tilden wrote way back in the 1950s when he was heavily involved with the National Parks Service:

‘Through interpretation, understanding. Through understanding, appreciation. Through appreciation, protection.’

Which is to say you can’t hope to protect a thing unless you (a) know about it in the first place and (b) understand why it is worth your attention. But it’s never enough to simply read someone the plain, dry scientific facts and hope that they ‘get it’. You need an emotional hook, something to pique their interest, something the public can relate to and get misty eyed about.

The green blanket at Ariundle

Hence the ‘Celtic Rainforest’. I first heard that phrase five or six years ago at college, and I remember it catching my imagination at the time. How could it not? It sounded so mysterious, so romantic, so remote, and I don’t mind admitting that the evocative name hooked me and reeled me in. Would my imagination have been caught quite so readily if it had been called by its more ecological term, ‘Atlantic woodlands’? Or would I have even considered visiting if it was known by a much more accurate description, say ‘’Sopping wet on at least 70% of days’ woodlands’? Hmm.

The romantic hook undoubtedly encouraged me to explore my first few Atlantic woodlands but, as sufficiently enigmatic places in their own right, it is the intriguing and surreally beautiful scenes contained within them that keep calling me back. And so I would encourage you to embrace the Celtic Rainforest and pay it a visit yourself, to see what makes these weird and wonderful woodlands special and to learn about the efforts being made to protect and link them together.

And of course I would heartily recommend that you choose a sopping wet day for your visit. I won’t lie, I got soaked through to the skin during my visit….but I didn’t care. For when the moss is deep green with moisture, the droplets of water bead on every surface, and the burns tumble noisily over rocks and stones, these places look and feel their absolute soggy best.

Walkhighlands route: Ariundle Oakwoods circular

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