|
The TreelineBen Rawlence |
A hectare of trees is needed just to get one squirrel through the winter
A Scots pine seed looks a bit like the wing of an insect, with a hard seed case and a long papery wing acting like a sail to catch the breeze. The seed endosperm crop is an essential food source for crossbills, siskins, tits, woodpeckers and red squirrels. Red squirrels shred the scales to get at the seeds, eating up to 200 cones a day. A hectare of trees is needed just to get one squirrel through the winter. […] Rodents and insects love pine seeds so a forest must produce a seed crop larger than the appetites of the rest of the food chain if it wants its seedlings to stand a chance. This seems to be the reason behind synchronous mast years - when all the trees produce a spectacular crop of seed at the same time.
Scots pines synchronise their flowering over 200 miles
Not only do Scots pines give their pollen the best possible start in life, they also synchronise their flowering across distances of up to 200 miles. How do they know? Ecologists have suggested hormonal communication on the wind, as well as via fungal networks underground, or it could be a deeply embedded genetic trigger activated by certain climatic thresholds. But no one really knows yet.
Ferns and mosses will grow with global warming
In Siberia rampant moss is already hindering the establishment of larch seedlings. The accumulation of carbon dioxide acidifies the soil, in the same way that CO$_2$ acidifies the ocean, suffocation other plants.
Implied violoence of brutalist forest architecture
The palette of the hill is red with moss, pink from the granite, bright green with shoots of blaeberry, the orange and red and white of lichen, all set against the blanket grey of heavy rainclouds pressing down. Below me the forest is an unending green, punctuated by trucks on the highway and the iron grey of the River Spey looping through the trees. Far off are the bare burned-brown grouse moors and the geometric blocks of plantations that now appear to me to have all the implied violence of brutalist concrete architecture.
Trees can see and hear
Monoterpenes are volatile organic chemicals produced by pines that the trees use to send signals to each other - to deter herbivores or insects or to coordinate seed release. Monoterpenes are tiny molecules that carry pine scent and bounce sunlight back into space. When pines are metabolising in sunlight there can be as many as 1000-2000 particles per cubic centimetre in the air around the tree, reducing the amount of solar radiation hitting the earth. Via the density of the chemical signal and the availability of light, they can detect the presence of other trees. In fact, they see the space in polygons, growing away from their neighbours and towards the light, creating a five-sided tesselation in the canopy that is the basis of self-organisation in the forest${}^{10}$. Through the structure of their cells, trees can capture reverberations and ‘hear’ sounds around them as well as ultrasound far away${}^{11}$. Pines can detect the familiar presence of rustling needles or the crack of a falling tree, and of course they communicate and look after each other through the rich mycorrhizal network underground. Scots pines have one of the most developed fungal networks in the soil, with over nineteen known ecto-mycorrhizal relationships for sharing carbon, nitrogen, eseential acids and other nutrients.
The shift from rights of usage to rights of ownership
The shift from rights of usage to rights of ownership, seen as the mercantile spirit of northern Europe inveigled or imposed itself across the world, was, it seems, the crucial shift, as forests ceased to be seen as sacred places of wonder, mystery and sustenance and instead became a standing crop with a value expressed in pounds, shillings and pence calculated by the acre and the ton.
The real tragedy is the enclosure of common land
The so-called tragedy of the commons (that humans cannot be trusted to manage a common resource sensibly) might be a problem for individualistic societies unable to restrain pollution and over-exploitation, but as a histrocial explanatio for the British landscape it doesn’t hold except perhaps as a retrospective ideological justification for the real tragedy to follow: the enclosure of common land.
In any carbon cycle, death is the engine of life.
Twisted pines grow in the most unlikely of cracks in the rocks. Dead trees, standing and fallen, are everywhere. This is the signature characteristic of wildwood - dead trees are allowed to rest where they fall. Dead trees support far more life than living ones, hence the density of bird life. Some species like tree pipits and redstarts associate only with old-grown forests because of the volume and species of insects. The great spooted woodpecker nests only in dead Scots pines. Even more niche, the pine hoverfly breeds exclusively in wet hollows of dead Scots pines. No wonder it is almost extinct in Scotland.
Scotlands signature landscape - the bog - is a ruined landscape
Rackham argues that pine wood never stretched from shore to shore., but it certainly covered most of Scotland until Mesolithic humans began to clear the forest for agriculture, hunting and construction. Managing the forest rhrough felling, clearing or burning for game played a role in creating biodiverse habitats of heath and moor, but also set the stage for the creeping blanket bog that has become upland Britain’s signature landscape. The bog is, in a sense, a ruined ecosystem as tree clearance has allowed minerals and iron to be washed into the lower layers of the soil, creating a pan impermeable to water. Unable to drain, the rundra-type landscape becomes waterlogged, and plants do not fully decompose, forming peat.
Migration of Scots pine to Scotland supported by humans
Before driving north, I read a scientific paper by Lithuanian researchers demonstrating that the DNA of Scots pine in the eastern half of Scotland came from a refugium - a place where species survived the last ice age - near Moscow around 9000-8000 BCE. Previous DNA analysis has shown that the surviving pines in the west of Scotland came from the Iberian peninsula in modern-day Portugal and Spain. In both cases the seed migrated to Scotland on timescales hundreds of times faster than is possible through natural succession. The most likely vehicle for such rapid migration was humans.
The first expression of an economic system founded on overreach
The Romanes, Danes and the nobles of England were in search of natural resources, principally timber. The colonisation of Wales was the first expression of an economic system founded on overreach: having exceeded the limits of what their own environment could sustain, early mercantilists applied force to acquire tribute and resources elsewhere. Empire, whether British, Viking, Roman or otherwise, is by definition overreach. And colonialism, capitalism and white supremacy share a common, perverse philospoph: limits on some human’s freedom of action are seen as an affront to the principle of freedom itself. The excat opposite of the co-evolutionary dynamic of the forest.
The elite six boreal tree species
It was only when I discovered that a tiny handful of tree species make up the treeline that I began to see that an attempt at description might be possible. An elite club, the six featured here are the familiar markers of the northern territories: three conifers and three broadleaves evolved to survive the cold. Moreover, remarkably, each of these tree species has made a sectio of the treeline its own, outcompeting other species and anchoring unique ecosystems: Scots pine in Scotland, birch in Scandiavia, larch in Siberia, spruce in Alaska, and, to a lesser extent, poplar in Canada and rowan in Greenland.
But now the planet is hyperventilating
But now the planet is hyperventilating. This bright green halo is moving unnaturally fast, crowning the planet with a laurel of needles and leaves, turning the white Arctic green. The migration of the treeline north is no longer a matter of centimetres per century; instead it is hundreds of metres every year. The trees are on the move. They shouldn’t be. And this sinister fact has enormous consequences for all life on earth.
The treeline is a moving target
The fact that in modern usage the term ‘treeline’ has come to mean a fixed line on a map indicating the growing limit of trees is simply evidence of the very narrow time horizon of humans, and of how much we have come to take our current habitat for granted.