Rebroadcast: How climate change is moving the world's forests north
This rebroadcast originally aired on May 20, 2022.
The great boreal forests of the planetary north circle the Earth in an almost unbroken ring.
Ben Rawlance has walked or canoed through many of these woods. But in Norway, above the Arctic Circle, Rawlence felt alarm.
At the forest’s edge looking North, Rawlence should have seen nothing but ice-white tundra, too cold for trees to grow.
But instead, he sees the dark forms of birch trees that have taken root in the ice.
“The different species of tree are responding to warming in different ways,” he says. “But the basic principle is like a greenhouse. You’ve heard of the greenhouse effect and greenhouse gasses, and if you put a plant in a greenhouse, it grows faster and higher. And that’s essentially what’s happening to the forests of the world.”
Today, On Point: The trees are on the move. Climate change and the world’s boreal forests.
Ben Rawlence, writer and founder and director of Black Mountains College in Wales. Author of The Treeline: The Last Forest and the Future of Life on Earth. (@BenRawlence)
On the spruce forests of Alaska
“Just across the border in Canada with the Anishinaabe people … and those old growth forests that have been there ever since the retreat of the last ice age. The ice sheet at the end of the last ice age. Have succeeded and grown and followed their own algorithm over thousands of years. And walking through, I felt a bit like I was underwater. There are these huge springy broccoli heads of lichen almost up to your knees, and it feels like you’re walking on a sponge. And then meanwhile, there’s all these different layers.
“There’s the shrubs, there’s the Labrador tea, there’s the different kinds of berries. And then above you, of course, is not just the spruce, but the jack pine that goes alongside it. And every time you move, you have these shards of light as if you’re on stage. And you’re walking through a kind of strobe light, while at the same time your ears are full of the humming of all these different insects, the calls of different birds.
“And then there’s … the trees themselves, and every tree has a different noise as the wind moves through the needles in different ways. So those old growth experiences are very, I think, few and far between for some of us, certainly us in England, we don’t have very many of them at all. But it’s kind of all-consuming and very, very moving.”
On the role that the boreal plays
“The boreal has a third of the trees on planet Earth. It has far more trees than all the rainforests of the world put together. And it isn’t just oxygen. There’s so many other functions. So I think the first thing to understand is the scale. We’re talking about half of Russia, half of the North American continent. This is an enormous amount of land which is covered in this forest.
“And then the situation of where it is, ringing the northern hemisphere in that way, is critical. Because you have these boundaries between the ice and the boreal. And then between the temperate savanna lands and the boreal. And you get huge differentiations in temperature gradient and in transpiration.
“So those trees are breathing every day, and every night. And obviously every summer and every winter there’s another cycle going on. And that creates a lot of moisture going up into the atmosphere, along with all sorts of other volatile chemicals. And you get these huge weather patterns that then are driven by the function of the forest. So the jet stream has a clear relationship with the breathing of the forest, as well as the temperature gradient between the ice and the forest.
“You then also have the huge function, cleansing function that these trees perform. So what I think is often missed is that it’s not just the breathing in carbon dioxide and breathing out oxygen, but that oxygen, when it’s transpired, the trees are also shooting out all sorts of cleansing chemicals, antibiotics. … They’re cleaning the atmosphere like a comb and performing all these functions that are humming away in the background that we’re scarcely aware of. And the last one is water, of course.
“So you may have heard this, your listeners may have heard of this concept of flying rivers. But when the trees transpire, they’re creating a vacuum. And that vacuum sucks in air, especially from the oceans. And sometimes, so from the coast, for example, of Alaska, all the way inland. That rain may have fallen ten times and then been re-transpired and sucked inland again.
“So the trees are actually like a kind of conveyor belt pulling water inland and they have an intimate relationship both with other parts of the continent. So there are … connections, for example, between the boreal and the Midwest grain belt, also between the Amazon and the West African monsoon. And then lastly, that water is discharged into the Arctic Ocean. The Pacific the Atlantic has a key role in the Arctic pump and the overturning of the ocean. So it has its absolutely essential role in the climate of our northern hemisphere.”
How climate change is impacting this critical planetary system
“Well, the answer is it’s patchy. And in some places we understand more than others. And actually Alaska and North America is one of the places where this has been studied in most depth and for the longest period of time. So we do have a quite a clear picture of what’s happening. It’s quite easy to see where the tree line is moving. It’s less easy to understand sort of the implications for carbon sequestration, permafrost collapse and things like that.
“Those are the much more intangible unknowns. But I think it’s fair to say we know enough that we should be really alarmed, and we should be doing all we can to protect it. But what was stunning to me was we’re used to this sort of idea of, you know, trusting the science. And that science probably has most of the answers. And certainly the activists are always saying, we just need to listen to the IPCC and the climate scientists and so on.
“But actually how rich the debate is among scientists and how, not about the fact of climate change, but about how it’s unfolding and what we’re modeling and what we’re not modeling. And in particular, I think the one big sort of shock for me was that, you know, there are three stations in Siberia that are monitoring methane release, for example. And methane is absolutely the joker in the pack in terms of climate forcing and temperature. So in some cases we know a lot. And in other cases, there are very big gaps which, you know, which should give us pause.”
On the treeline moving north
“There’s currently quite a lot of debate around, What was the history? Because there’s a lot of effort to plant trees and lots of companies are spending a lot of money on planting trees. On the assumption that we are rewilding, we are taking the forest back to its wild heritage. Meanwhile, you have Grouse Moors and … forestry plantation owners who are saying, you know, that’s not natural. It was never like that. This is more natural.
“And the irony is it was none of those things. It was actually an oak forest. And the pine was brought by brought by the humans. But the point about the zombie forest is it doesn’t really matter anyway, because nature has its own algorithm, its own equation. And at the moment the UK is effectively moving south at a rate of around 12 miles a year.
“So that’s our climate velocity based on the temperature. So it’s like we’re moving towards Southern Europe. And by at least 2050, if not before, London will have the temperature that Barcelona has had until recently. … And what that means for the trees is that, you know, up until quite recently, people used to think that the tree line in Scotland was somewhere around about 700 meters. So what’s that, 2,100 feet?
“But as the tree line now is moving north at quite a rate, it could be that by the end of this century, the Scots Pines are below the growing limit for pines. It’ll be too dry, it’ll be too hot. And actually the Scottish pine forests will have zipped north and will be somewhere in Iceland, or even if it’s there, if it can establish in time. So the zombie forest is, you know, there’s all this argument about the rewilding of the Scottish forest, but meanwhile the clock’s ticking, unfortunately.”
The Big Issue: “‘As the planet warms, the forest is on the move’” — “You have a heartbeat. Did you know that the planet has one too? In fact it has more than one.”
The Guardian: “‘The treeline is out of control’: how the climate crisis is turning the Arctic green” — “Altafjord is a wide expanse of black water on the edge of the Barents Sea, ringed with mountains.”
This article was originally published on WBUR.org.
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