The dark side of the woods

Our liking, or even passion, for trees has led to the consultation by the Scottish Government on whether Scotland should have a national tree and, if so, what this tree should be. There is a strong lobby in favour of it being the Scots pine. Certainly "granny" pines, ancient at up to 500 years old, with their flat-topped crowns, wide-spreading branches, dark green foliage and orange bark, are beautiful to behold, especially when set against a backdrop of loch, glen or hill. Indeed, in recent years Scots pines have perhaps become icons of the Scottish Highlands, even of the Scottish countryside itself.

However, when we think of the Highland landscape, this dominance of Scots pine in our imagination is surprising considering that, at the beginning of the 20th century, when woods covered only 4% of our country, pinewood covered a miserly fifth of 1% of the Scottish land area - yes, only 0.2% of Scotland. So why do pine trees have such a hold over us? One reason is that, lodged in the Scottish people's mind, is the idea of the "Great Wood of Caledon", the idea that Scotland was once clothed from coast to mountain-top with forest - and it was all destroyed by our ancestors, much like we are cutting down tropical rai forests today. Hence an argument used for increasing the number of trees is that, because humans destroyed this Caledonian Forest, there is almost a moral imperative for us to put it back. Planting Scots pine, or any native tree, is doing our bit to "save the planet".

Expanding the woodland cover of Scotland is, in fact, the policy of all conservation organisations. For example, the charity Trees For Life's vision is to "restore Scotland's Caledonian Forest". The Woodland Trust, John Muir Trust, Scottish Natural Heritage and Scottish Wildland Group all wish to see increased woodland cover.

The RSPB wants to expand its Abernethy native pinewood through planting, while the Cairngorms National Park Authority states that "woodland cover should be expanded through habitat networks ... [with] the creation of new forest nuclei". The list of organisations in favour of woodland expansion goes on and on. And people can get very emotional about the subject. The environmentalist writer and campaigner George Monbiot, for example, wrote recently that our open hills, devoid of trees which were once cloaked in forests that we have destroyed, are a "blasted, impoverished land".

Restoring the Great Wood of Caledon would be a valid argument if humans had, in fact, destroyed such a forest but the evidence for this is thin - we just know it because we know it. Although there are certainly some areas where the evidence supports human destruction of woodland, there are also areas where our presence caused woods to be conserved or even expanded because of their economic importance. It is said that the large post-Clearance sheep farms caused the woods to disappear, any young trees all being eaten by sheep and so preventing the wood regenerating. However, woods were rare in the landscape even before this era, so the sheep cannot be to blame; and in earlier times there would have been wolves in the landscape making it impossible to keep free-ranging grazing animals in the hills.

With the recent decline in sheep numbers, the blame for lack of trees is put down to deer: "there are too many deer" is the mantra and their numbers must be brought down to allow the woodland to recover, particularly as they have no predators to control them. In fact humans are a major predator of deer, and wolves would have to eat more deer than are shot by stalkers to keep their numbers down, which seems unlikely. It is possibly true that, if wolves were present, they would move deer around, allowing trees to grow in some places but the fact remains that the trees in Scotland largely disappeared in the period when wolves were present. Deer certainly do damage trees: but rather than being a problem, they are merely a shaper of the ecology of Scotland.

Of course, humans could have just cut or burnt down the original forest, causing it to disappear. However, much of upland Scotland has always been very remote with a low population density, and a simple question is: if the humans removed the trees, why did they not regrow again?

No, the reason for woodland naturally being rare in the Highland landscape is explained in one of the Forestry Commission's own information notes: "A combination of very low soil nutrient availability and high soil moisture provides very unfavourable conditions for colonisation of birch, rowan and Scots pine."

I actually think it is more complicated than this, with grazing and other factors also playing a part but the essence of my case is stated there: the simplest explanation for why most of the Highlands are open moor rather than forest is that trees find it hard to perpetuate themselves here. There are exceptions to this, particularly along the coastal fringe where woods can regenerate freely.

Undoubtedly there were more trees in Scotland following the ice age; indeed, as anyone who has ever cut peat or walked the hills will know, stumps of ancient pines can be found in bogs in many areas where there are no trees today. However, these stumps generally date from 4000 to 5000 years ago and were often relatively short-lived forests that expanded then died out naturally.

Research suggests that, following an ice age, woodland can expand only to decline over time irrespective of human influence. The organisers of a conference on native pine woods in the 1970s concluded that pine woods may be an endpoint, "before return to open moorland as a result of soil degradation".

However, the concept of the Great Wood has been around since Roman times and we in Scotland just take it as unquestioned truth. This is in spite of the fact that Scotland's most distinguished historian, Historiographer Royal, Professor Christopher (TC) Smout, has dismissed it as a product of our imagination. "Let us begin with the Great Wood of Caledon," he writes in Nature Contested, his environmental history of Scotland and northern England. "It is, in every sense of the word, a myth." Likewise, the historian David Breeze, in his paper The Great Myth Of Caledon, argues: "Roman descriptions do not allow the forest to be located with any exactitude; the sceptic might even doubt whether it ever existed, and that all we are dealing with is a myth repeated by many writers."

So why does the myth of the Caledonian Forest, together with the importance of Scots pine in the landscape, still dominate our thinking? So much so that the Government's Scottish Forestry Strategy commits us to covering a quarter of Scotland with trees. Certainly, emotion is involved: the term "Scots pine" has the word "Scots" in it and the phrase "Caledonian Forest" has a nationalistic ring. In fact Scots pine is probably so called because it is not found naturally in England; however it is the most widely distributed conifer in the world, being found all the way across Europe and Asia to the Sea of Okhotsk in the Far East.

So what is the problem with putting more trees into the Highland landscape? Fundamentally, if humans did not destroy the once mighty Caledonian Forest and trees largely disappeared through natural causes, then the area can hardly be described as a "blasted, impoverished land". In fact, it may well represent one of the few remaining natural vegetation patterns in Western Europe and, as such, should be prized by conservationists. Our Scottish open hills and moors, which contain an unbroken link back to the ice age, should be put in the same category as tropical rainforests, mangrove swamps and arctic tundra: any human intervention which reduces their naturalness, such as planting trees, will reduce their conservation value.

By choosing to expand Scots pine forest we are, in fact, creating a common European woodland type, thereby displacing open moorland which is rare in Europe. We humans tend to give more value to the rare than the common: hence, with woodland rare in the Scottish landscape, we give it greater value than the abundant open moorland. And the general feeling is, although it is a non sequitur, if some is good then more must be better.

The "restoration of the Caledonian Forest" rationale is still commonly used to justify this expansion. Curious to know what the Historiographer Royal makes of this argument, I contacted Professor Smout last week. "When Scots pine is planted in places where there has not been any for millennia, then this is not so much restoring a lost ecosystem as creating a new one. That is not necessarily a bad thing," he replied.

"But it is wrong to say that it is an accurate historical restoration, since the entire climate and ecological circumstances were different to what they are now." In other words, there might still be a case for woodland expansion, but it should not be based on the "restoration" argument. So what are the other arguments that conservationists use?

One justification put forward by the Government and others is based on the fact that Scotland's woodland cover is way below the average for European countries, and hence we need to raise it. The logic eludes me. Italy has fewer peat bogs than the European average; should Italy create more bogs? Austria has fewer sand dunes than the average; should these be created? Our glacier cover is less than the Scandinavian average; should we have more glaciers? In any case, why are we trying to make Scotland look the same as most of the rest of northern Europe? Why are we not instead trying to conserve our own distinctive open hills and moors?

Another argument put forward for more woodland is the vague notion that woods are good for biodiversity. Well, heather moorland is also good for biodiversity. Pine woodland and the open habitats of wet heath, dry heath and bog are all recognised as important for biodiversity in European terms - and expansion of one will be at the expense of another. Why is woodland more important? Because it is rarer?

It is also argued that linking together isolated areas of woodland is a good thing, as it allows wildlife to move around the landscape: however, the end result of such a network of woodland is to fragment the existing network of open moorland. Is it sensible to destroy one network to create another? Perhaps, once moorland becomes rare because of all the tree planting, then people will say it is important, and trees must be cut down to make more of it.

With climate change in the news, another argument put forward for woodland planting is that it helps slow down climate change through the trees storing carbon in their wood. However, while a valid concept in many parts of the world, one has to be wary of assuming this to be the case in Scotland - where most trees are being planted on carbon-rich soils which generally store more carbon than the trees themselves. In fact, trees can cause the soil to dry out and so release this carbon into the atmosphere.

There is, though, one rather more credible argument: we all use wood and need more timber. This I can understand, but society will have to decide how much more of our distinctive open hills and moors we are prepared to lose to commercial forestry plantations.

If the Great Wood of Caledon is a myth, and most woodland died out naturally over the millennia, then there is no real case for woodland "restoration". Indeed, covering our globally rare heather moorland, and all the other moorland types, with trees is causing a loss of the distinctiveness of Scotland. Moorland may at times be bleak and windswept, blasted by rain or snow, or enshrouded in mist, but its open, free-ranging and cloud-studded landscapes have given the people of Scotland a wide perspective: it is the "old Scotland" which nowadays we are wanting to smother with a modern, imported culture of woodland.

No, I am not convinced that there is a strong need for Scotland to have a national tree, although if there has to be one I would recommend the rowan or birch, which are common throughout and so characterise the country. Instead I would suggest that heather should be the national plant, or perhaps "national shrub" if height is important.

Do not get me wrong: I like our native woodlands. But we are the world centre for heather and it is open moorland that makes the Scottish countryside distinctive. And we seem determined to destroy it.

Consultation on a national tree for Scotland continues until December 3. To contribute visit https://consult.scotland.gov.uk/forestry-commission-scotland/national-tree