Stand on the summit of any munro and you’ll gaze out across a land of bog, rock, heather and grass. Sometimes it looks so timeless and primeval that it’s tempting to believe it has always had that stark, treeless beauty. But it’s an illusion. One that our hills almost manage to pull off, were it not for certain unexpected objects that shatter the illusion completely.
Last week I was working my way around Beinn Bheag on Beinn a’ Ghlo when a skeletal object caught my attention just off the path. Bleached grey-white by age and the elements, half buried within the dark brown soil, it was a large solitary tree stump. In a landscape devoid of trees, it stood out like a sore thumb.
Where did it come from? Where did it go? Was it part of a forest? If so, what happened to it?
The fall of the forest
Around 11,000 years ago the most recent ice age was relinquishing its grip on what is now Scotland, and the ice caps and glaciers were melting. A steady succession of plants and animals moved northwards across the land bridge that still linked Europe to mainland Britain, colonising the barren post-glacial landscape.
It took thousands of years but eventually much of Scotland was covered by forest. Not just Scots pine but a mix of broadleaf trees like oak, birch, rowan and aspen.
The forests’ extent fluctuated naturally over the millennia as the climate warmed and cooled, but most sources seem to put their peak extent at between 5000 and 6000 years ago. Some time thereafter the climate got significantly cooler and wetter.
With higher rainfall the ground became waterlogged and nutrients were washed out of the soil. Trees died, the great forests contracted or became fragmented, and the tree line crept down off the hills and into the glens as the conditions at altitude got less hospitable.
Whether or not the forests would have recovered naturally when a warmer, drier climate returned is open to debate, because from around 6000 years ago onwards, Neolithic humans started to clear or burn the remaining forests for grazing and farming. Their livestock would have foraged on young tree saplings and prevented the forests from regenerating naturally. When big old trees grew old and died there would have been no youngsters to take their place.
Certainly, the kinds of activities that the Neolithic inhabitants of Scotland indulged in made a natural recovery of the forest unlikely. But while humans are widely acknowledged as being a contributing and long-lasting factor in our forests’ demise, it also seems to be the consensus that Scotland’s forests were already in a period of decline before humans started to have a significant physical impact upon the landscape.
Crucially, the cooler, wetter conditions favoured the formation of bogs and a special kind of soil. One that is especially good at preserving objects for later study. One that hillwalkers in Scotland are all too familiar with. Peat.
Cross section of peat bog on Mount Battock
The rise of the boot-sucking sponge
Physically, peat is an ominous spongy wet mass that sucks at your boots, but fundamentally it is the remnants of countless dead plants.
When trees or plants die, decomposers such as fungi, invertebrates and bacteria start to break them down by feeding on the dead or decaying matter. They need oxygen in order to do this because they, like us, breathe. On the surface, exposed to air, or in soil that isn’t waterlogged there is plenty of oxygen for decomposers to go about their business. In waterlogged environments there’s hardly any oxygen at all. Decomposition is therefore very slow or non-existent in those cold, wet, sterile environments.
When the few plants that can survive in waterlogged conditions die, such as sphagnum moss, they accumulate faster than they can be broken down. Layer upon layer of dead moss builds up to considerable depths and, over time, the moss gets compacted and forms peat; that familiar, bouncy, brown-black mass we lovingly trudge through in the hills.
1 metre in 1000 years
Peat’s sterile environment offers the perfect conditions for preserving organic objects but it needs to have covered the object in question in order to preserve it. And that’s no small feat.
The rate at which peat accumulates varies but in all cases it’s an agonisingly slow process. It typically takes one year for 1mm of peat to accumulate. That means it takes 1000 years to make one metre of peat, and a whopping 10,000 years to make ten metres of it.
If you find a tree stump close to or on the surface then it’s probably not very old. But if they look as though they have been exposed from within deep deposits of peat then the opposite could be the case.
The stump I found near Beinn a’ Ghlo was flanked by deep deposits of eroded peat. A couple of metres of it, certainly. We can’t know the stump’s age without carbon-dating it but hopefully you get a sense of just how old some of these skeletal tree remains might be. Indeed, many peatland tree stumps in Highland glens have been properly carbon-dated and were found to be in the region of 4500 years old!
Now they stand as relics in the landscape, thought-provoking monuments to natural climate change or human interference, or both. Reminders of what was, and what might have been.
To burn or not to burn?
That is the question I wrestled with in a cold Sutherland bothy in January this year.
All the accounts I’d read beforehand and many of the entries I read in the bothy visitor book once I arrived said there was a plentiful supply of bog wood nearby. Thankfully, previous visitors had already gathered a lot of the wood and left it by the fireplace, dry and ready to use. Indoors, in the dimly lit room it looked like any old driftwood you might find lying about.
It was a subzero night so I didn’t think twice about burning some of what was there. The fire kept me warm and, the next morning, I headed out in search of the bog wood source to dutifully replace what I’d taken.
Expecting to have a long, hard search for just a few scattered old roots poking out of the peat, what I actually found was an entire forest! It was (and still is) the largest collection of ancient stumps I’d ever seen, and it stopped me in my tracks.
The ghostly forest
The distant past is often hard to visualise or relate to because the timescales are so huge, but bridging those huge gaps is possible when the past is standing there right in front of you in a form you can easily recognise.
Seeing that forest of stumps it wasn’t such a huge leap for me to picture the trees standing once more, with all manner of extinct animals prowling and foraging among them. I pictured the glen as it had once been and a previously intangible era in Scotland’s natural history felt close enough to touch.
Suddenly the reality of what I had come to collect (and later burn), hit me. As I gathered individual pieces of wood from amongst the ghostly remains I couldn’t help feeling I was committing some sort of crime. How could I burn something so ancient?
Later, as frost formed on the outside of the bothy windows and wood crackled on the fire, I told myself I was being silly. I reminded myself I was also burning stuff much older than the wood. Other previous visitors had left some coal, and it smoked pleasingly on top of the wood. Coal, the very thing peat can turn into given a few hundred million years and a bit of heat and compaction.
Evidently, antiquity in itself wasn’t a convincing enough reason not to burn the bog wood. The coal was ANCIENT but I hadn’t thought twice about burning that. I reasoned that the coal was difficult to love. It was black, dirty, and it bore no resemblance to the tropical environment in which it was produced. You can’t look at coal and have the past vividly appear in front of you. The ghostly remains of a forest, however……
I then tried telling myself I had only taken a few scattered bits of root, but I still wasn’t convinced. I knew there was plenty more wood where that came from but I also knew that more people would come after me, more people would raid after me and, eventually there would be nothing left.
I realised it wasn’t merely the stumps’ antiquity that bothered me. It was also the fact that they are finite and irreplaceable, and it saddened me to think that future visitors to that Sutherland glen mightn’t get the same vivid encounter with our past that I’d experienced that morning. It was a ghostly museum. And now it was haunting me.
I sat staring pensively at the flames as they danced around the charred remains of the ancient wood, before letting the fire die down and climbing into my sleeping bag. Heat quickly left the room. A full moon streamed bright light through the window, lighting up the frost on the glass. Gawd it was cold!
Bog wood warming the bothy