The public perception of Sitka stands is lifeless blocks of dark, dense woodland, devoid of wildlife. But how can that be true when so many species of birds have been shown to thrive among the trees?
YOU only have to read the pages of Forestry Journal to see that Sitka spruce as a plantation conifer is attacked and castigated on all sides, with some pretty extreme descriptions including ‘dark and satanic’ which appears one of the most popular; and even claims by an Irish farmer in Leitrim that Sitka spruce adversely affects your mental health.
A focus of the fear-mongering revolves around allegations that Sitka spruce forest plantations do not support wildlife and create a void in biodiversity. There are continual calls to stop planting the trees in Scotland where the species has rescued Scottish forestry and in doing so essentially saved commercial forestry in the United Kingdom, because frankly nothing substantial and worthwhile has happened in England and Wales for years.
No mean feat for a conifer plucked from the other side of the world from its natural home in western North America. Sitka spruce has taken to the mild and moist maritime climate of the British Isles like no other introduced exotic conifer species. And don’t you think the forestry powerhouse nations of Central Europe would plant Sitka spruce if they had climate and growing conditions that allowed the exotic conifer to attain its full potential?
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So back to biodiversity and ongoing allegations that Sitka spruce snuffs out anything that is green, or moves and breathes. Whether you subscribe to these claims depends on what you read and what you want to believe. However, if you cast your reading resource net sufficiently wide and back far enough to avoid the ‘nutty noughties’ and beyond you will find you have been fed with ‘fibs’ on a grand scale.
Before I start, perhaps I should own up to minimal first-hand experience of Sitka spruce and no first-hand experience of Scottish wildlife, but that does not stop me delving into past studies by learned academics and hands-on foresters, many of whom were leading lights in the Forestry Commission going back several decades.
And one more thing, because there is a parallel in what was being said 20 years ago about conifers (mostly Scots and Corsican pines) planted and regenerating on lowland heathland across the south of England and East Anglia. Conservation organisations with apparent tacit approval of the Forestry Commission claimed pine plantations were impacting badly on the success and survival of two flagship birds of lowland heathland – the nightjar and woodlark.
Indeed, I got into a serious spat on the topic within the pages of Forestry Journal some 15 years ago. However, I did my research, with some going back to the 1950s, to show that providing there were blocks of pines at all stages of development (recently planted and newly established and right through up to maturity) then both birds were ‘as Happy as Larry’. The High Priests of lowland Heathland were casting spells but peddling untruths at the same time. All that said, what about Sitka spruce in Scotland and its relationship with native wildlife?
CAPERCAILLIE THRIVED UNDER SITKA SPRUCE
When it comes to birds, they don’t come more Scottish native and iconic than the capercaillie and if that bird can exploit Sitka spruce then what’s all the fuss about?
First port of call was a paper published in the journal Forestry in 1996 – capercaillie habitat, diet and management in a Sitka spruce plantation in Central Scotland; by N. Picozzi, R. Moss and D.C. Catt, and this is what they had to say: “The ancestral habitat of capercaillie in most of its range in Scotland is Scots pine forest with an understorey of blueberry. Keillour forest in Perthshire is dominated by Sitka spruce, has little blueberry, yet had a density of capercailie. Food and habitat used by capercaillie were studied there from 1991 to 1994. Seven cocks and two hens were caught, and marked with small radio transmitters. The habitats they occupied and food remains in their droppings provided information on home range, habitat utilisation and diet through the year.
“Sitka spruce was the main food in autumn, winter and spring, but was equalled by the fruiting heads of sedge in summer. Larch was the second most abundant item in spring and autumn diets. Sedge was plentiful on the wet restocks associated with gleyed soils at Keillour and may provide a partial substitute for blaeberry in summer.
“Capercaillie showed a clear preference for the oldest blocks of trees, especially in winter, presumably for cover. Sitka spruce, Norway spruce and Scots pine were used roughly in proportion to their availability in the birds’ home range, but larch stands were used more than expected from availability.”
UPLAND SITKA SUPPORTED A WIDE RANGE OF BIRDS
Sticking with birds, the next study is ‘Bird populations in upland spruce plantations in northern Britain’, published in Forest Ecology and Management (1996) by I.J. Patterson, J.G. Ollason and P. Doyle, which looked at a much wider range of birds across three study areas – Cowal, Argyll and Kielder, Northumberland. It measured bird numbers and species in upland spruce forests in relation to forest habitats, as the basis for a computer model to predict how populations were likely to change under different management regimes. And this is what they had to say.
“There was strong and significant variation in bird numbers and species richness with tree age, both being highest in older trees in winter and in 9–25-year-old trees in spring. All of the common species—chaffinch Fringilla coelebs, coal tit Parus ater, crossbill Loxia curvirostra, dunnock Prunella modularis, goldcrest Regulus regulus, meadow pipit Anthus pratensis, robin Erithacus rubecula, redpoll Carduelis flammea, siskin Carduelis spinus, song thrush Turdus ericetorum, tree pipit Anthus trivialis, wren Troglodytes troglodytes and willow warbler Phylloscopus trochilus were present but showed significant variation in their abundance between tree-age categories, with all except the meadow pipit having lowest numbers in the youngest trees and their highest in 9–25-year-old trees.
“There was little detectable effect of plot size, altitude, admixture of other conifer species or planting generation on either bird numbers or species richness. The number of individual birds detected was consistently higher at the edges than in the centres of the same plots, particularly in the first 10 metres from the edge, but the type of habitat outside the plot had little effect on this.”
The study clearly identified tree age and closeness to the forest edge as the two main factors affecting the number and species richness of birds in upland spruce plantations. This suggests that the greatest number and variety of birds could be encouraged by creating mosaics of small patches (i.e. with a high ratio of edge habitat), with a mixture of tree ages, including a large proportion of 9–25-year-old trees.
These are just two of many research projects carried out over the last three decades which clearly show Sitka spruce can support native wildlife, in this case birds. A common thread appears to be the management of Sitka spruce plantation in ways appropriate to the encouragement and support of wildlife. Clearly you don’t have to eradicate Sitka spruce from the landscape, like all sorts of lobby groups are calling for, but manage all aspects of growth and production to maximise benefits to wildlife while maintaining the yield potential of this unrivalled softwood timber-producing tree.
STILL NOT CONVINCED?
Still not convinced about the benefits of Sitka spruce and its ability to support wildlife?
Then take a look at this trio of snapshots from Forestry and Land Scotland, which actually say the expansion of commercial forestry using Sitka spruce has allowed the establishment of erstwhile extinct avian species while allowing others to flourish.
THE GOSHAWK
The goshawk is one of our most striking and threatened birds of prey. A century ago, it was persecuted to extinction in Scotland. Today, however, goshawks are staging a remarkable recovery. Thanks to careful conservation, there are now more than 100 pairs north of the Border. Nowhere are they more at home than in some of our biggest and most productive forests of Sitka spruce.
THE WHITE-TAILED EAGLE
A breeding pair of white-tailed eagles has set up home in Caithness woodland. The birds, thought to be the first successful breeding pair in the area for almost 100 years, were found nesting in a stand of Sitka spruce trees within a windblown area of lodgepole pine. It’s believed the eagles selected the Sitka because it offered a stronger platform on which to build their eyrie than the neighbouring trees.
COMMON CROSSBILLS
Within northern Europe, common crossbills depend on Norway spruce seeds for food. The Norway spruce cone crop varies enormously between years and the variations are synchronous across a wide range. In years when no cones are produced, we see irruptions of crossbills to regions south of their normal range. As Norway spruce isn’t native to the UK, previously irrupting common crossbills arriving from Fennoscandia and Russia could only forage on the tough woody cones of the native Scots pine. This was until the introduction of Norway spruce and Sitka spruce (a North American conifer) to enhance the national timber crop. Now, Sitka spruce makes up half of the woodland area of Scotland, whilst Norway spruce comprises only 3 per cent. Sitka spruce in particular has helped common crossbills become established in the UK as a breeding species.
JUST A SNAPSHOT
The above is just a snapshot of the wealth of research conducted over the last three decades and earlier into the way wildlife (in this instance birds) can exploit Sitka spruce plantations to its advantage. No-one is denying that plantation Sitka spruce trees grow close together, forming a dense canopy which few plants can grow beneath. That’s the downside. But the dense foliage provides cover from the wind and rain for larger mammals, while birds of prey and smaller birds, such as crossbill, tree creeper, coal tit and siskin, may use Sitka spruce for nesting.
The research highlighted here was conducted by forest scientists and wildlife scientists recognised as the best of their day, with many actually working for the Forestry Commission and Forest Research. However, you have got to wonder why – a generation down the line – this wealth of evidence is ignored and/or dismissed because it doesn’t comply with contemporary thinking about Sitka spruce, its role in forestry and its position on the landscape.
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