Treeline Racing North In Norway; Movement Had Been Centimeters/Year, Now It's 40-50 Meters Per Annum
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As the planet warms, the Arctic treeline is accelerating towards the pole, turning the white landscape to green. The trees used to creep forward a few centimetres every year; now they are leaping north at a rate of 40 to 50 metres a year. In the European Arctic, the birch is the leader of the pack. Downy birch is one of few broadleaved deciduous trees in the Arctic and it is hardier even than most conifers. Its “down” is a soft coating of hairs that acts like a fur coat in the punishing cold. Often found cooperating with pines and spruce at lower latitudes and altitudes, above a certain point the birch leaves the others behind and goes on alone for hundreds of miles.
It might be unprepossessing, even ugly, with its stumpy branches and pockmarked bark, but this tough little tree is a survivor and a pioneer, essential to nearly all life in the Arctic. Used by humans for tools, houses, fuel, food and medicine, it is home to microbes, fungi and insects central to the food chain, and it is critical for sheltering other plants needed to make a forest. The downy birch dictates the terms of what can grow, survive and move in the areas in which it takes hold. And, as the Arctic heats up, that range is expanding fast.
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everal interlinked factors affect the habitable range of tree species: the availability of sunlight, water and nutrients are prerequisites, but these interact with other variables such as wind and temperature. Tiny gradations in altitude or latitude can mark large differences in vegetation. The downy birch detected the current warming trend much earlier than most scientists. This tree loves the warmer weather. It used to be confined to the dips and gullies on the plateau, away from the icy winds, but, unleashed by the warmth, it is storming over the top and out into the open, moving upslope at the rate of 40m a year. An enormous amount of territory is being transformed from tundra into woodland. On the face of it, more trees might sound like a good thing. The problem is that the greening of the tundra further accelerates the warming process, as the birch improves the soil and warms it with microbial activity, melting the permafrost and releasing methane – a greenhouse gas 85 times more powerful than carbon dioxide in its warming effects over a shorter timeframe.
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It takes 160 years for an old-growth pine and birch forest to form – one that is suitable for reindeer to graze in. In Norway, aggressive tree growth is now creating havoc. The birch is racing over the tundra faster than the pines can keep up. This is bad news for the reindeer and the humans who rely on them. Upright birch forests don’t develop a canopy; they are more like thickets. Without a canopy, they trap more snow, their mass forming a windbreak for drifts too deep for the reindeer to walk or dig through. Their roots warm the ground below, causing ice and melt around them. In time, a hectare of birch will deposit three to four tonnes of leaf litter on the ground, further improving the organic composition of the soil and encouraging other plants. Reindeer do nibble the twigs of young birch, “but even if you doubled the number of reindeer in Finnmark county you could not stop the birch”, said Sund.
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https://www.theguardian.com/news/2022/jan/20/norway-arctic-circle-trees-sami-reindeer-global-heating
