– Trees are our most important weapon in the fight against climate change, said Thomas Crowther. The reason is simple; trees capture CO₂. But not all trees are good news for the climate. – The trees around the tree line are so small that they have little vegetation above the ground. Thus, the albedo effect is greater than the effect of carbon storage. That’s what Eirik Næsset Ramtvedt at NMBU says. He has researched how trees in Norwegian mountains affect the reflection of sunlight. – This will affect global warming, he says to news. Snow reflects more Albedo in an area is therefore important for how much of the sunlight is left on the earth. Forests have an albedo of 0.15, ie much lower than snow. More of the sun’s energy remains on the earth if snow is replaced with forest. In large forests, carbon capture will offset less albedo. The same cannot be said of trees high in Norwegian mountains. – More trees will bind more CO₂ through photosynthesis. But the trees in the tree line are so small that it does not compensate for the albedo effect, Ramtvedt explains and adds: The further up the mountain you get, the smaller trees you will see. That there will be trees higher up is not necessarily good news. Photo: Sondre Skjelvik / news – When there are more trees and less snow in the mountains, less sunlight will be reflected back to the atmosphere. The fact that there is normally a lot of snow in Norwegian mountains makes the situation extra precarious. – In the Norwegian mountains, the albedo effect is extra strong, precisely because there is snow in the mountain areas throughout the winter. New trees that appear in the mountains will shade over the snow and absorb much more sunlight than the snow itself. Eirik Næsset Ramtvedt has, among other things, used drones to map how much sunlight is reflected back. Photo: Private A vicious circle But why are there more trees in the height? For the past four years, Ida Marielle Mienna has been researching what affects the tree line in Norway. She says there are a number of factors that make the trees thrive higher up in the mountains. – Temperature is an important factor, but there is much more. Trees depend on rainfall and access to moisture. In addition, we see an overgrowth in many places due to the drop-out of grazing animals. Ida Marielle Mienna has researched the factors that affect the tree line. Photo: NMBU An important factor for the tree line to move upwards in many places is that it gets warmer. More trees in the mountains again contribute to it getting warmer. – It’s a vicious circle. There is clearly cause for concern, says Mienna. Like Ramtvedt, she points out that the albedo effect means that more trees are not necessarily good. – More vegetation contributes to the capture of CO₂, but the albedo effect is large. We also see that many plants in the mountains are red-listed because the forest moves upwards. – Trees are not exclusively positive. Large forests are important for the storage of carbon dioxide. But small trees in the mountains can not absorb enough. Photo: Sondre Skjelvik / news The tree line moves quickly Several factors mean that there are more trees high in the mountains. But how fast is development happening? Anders Bryn at the Natural History Museum, together with Peter Horvath, has compared today’s wooden boundary with how it was 100 years ago. They have in fact compared new measurements with data Hanna Resvoll-Holmsen collected in the early 1900s. – Dense forest has moved about half a meter per year in Norway. The tree line has changed between half a meter and a meter, Bryn explains. Anders Bryn explains that the tree line moves relatively quickly. Photo: Even Lusæter / news – It is just so slow that many do not notice it. But if you have had a cabin in the same place for a long time, you may have noticed it. He explains that climate change is making things faster and faster. – The highest tree line we have now is at 1400 meters in Jotunheimen. The appearance of trees at 1400 meters is a small warning of what is to come. It will take a long time, but suddenly the Hardangervidda is below the tree line, he says and adds: – There is something to think about. Bryn points out that it is not only the albedo effect that makes this problematic. With forest comes, among other things, mushrooms. It helps to break down organic material. Photo: Nils Fridtjof Skumsvoll / news – In the mountains just above the tree line, a lot of organic material is stored that does not decompose due to low temperatures. With the trees, however, decomposing communities come in. – When this soil decomposes, more CO₂ is released into the atmosphere.
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affects global warming negatively – news Nordland
