bne IntelliNews – BOOK REVIEW: Climate Change at the Arctic Treeline

Trees nearly surround the North Pole, with vast forests stretching across Scandinavia, northern Scotland, Greenland, Canada, Alaska and largest expanse of uninterrupted forest northern Siberia and the Russian Far East. In The Treeline: The Last Forest and the Future of Life on EarthBen Rawlence travels to remote settlements along the treeline, tracing the gradual northward shift of forests into lands that were once too cold to support tree growth.

As the world grapples with the climate crisis, the importance of the world’s northern forests can hardly be overstated. After the oceans, it is the second largest biome in the world: it covers a fifth of the globe and contains a third of its trees. He also has despite the ravages of logging and ever more frequent forest fires has survived better than the Amazon, which according to one of Rawlence’s interviewees, author, medical biochemist and botanist Diana Beresford-Kroeger, is “finished”, while other rainforests are “severely degraded”. . This leaves the northern boreal forest as the “last forest” in the world.

However, climate change is also wreaking havoc in the Far North. The position of the Arctic treeline broadly follows the line around the globe where the average summer temperature is 10°C, but this no longer coincides with the Arctic Circle. Large forests move north as the land warms, invading the tundra in the north, while some southern parts of the forest become dry steppes. The place where Rawlence begins his journey, the Scottish Cairngorms, will be well south of the tree line by the end of the century.

Even in the northernmost forest on the planet, in Ary Mas in Russia’s far north, things are changing. Deep in the Arctic Circle, Rawlence reaches Ary Mas after a grueling journey across the tundra and frozen sea, finding a mixture of nostalgia for the old way of life and welcoming of new technologies among the Dolgans. Although the changes observed by residents of the region are minimal, there are clear differences: new species of birds migrating north, daisies and dragonflies appearing on the tundra.

Climate change is accelerating

Climate change is happening much faster than expected in Siberia; the wildfires seen in 2020 were not predicted until four decades later. That year, temperatures broke records and a massive toxic spill from oil tanks in the Arctic city of Norilsk was caused at least in part by melting permafrost.

Worrying developments continued in 2021 and 2022. Wildfires in taiga forests in Siberia and the Far East in 2021 were unprecedented, covering an area of ​​at least 18.8 million hectares, and for the first time the smoke from the fires reached the North Pole.

This summer, attention has been diverted to the war in Ukraine, but forests are still burning and states of emergency have been declared in seven Russian regions. The western part of the country was not spared either; In late August, fires south of Moscow blanketed the capital in smog.

At the Sukachev Institute in Krasnoyarsk where the author arrives on an abnormally hot month of February Rawlence interviews Nadezhda Tchebakova, a scientist modeling future scenarios for Siberian forests.

Chebakova’s model, based on scenarios from the Intergovernmental Panel on Climate Change (IPCC), predicts that while the northern tree will shift slightly poleward, “the real change has been the southern boundary of With increasing drought and more frequent fires, the steppe in central Asia was expected to expand, consuming the burnt taiga as it went, preventing it from regenerating.

The increased frequency of fires which used to erupt between five and 30 years apart and are now annual events means that instead of forests growing back after fires, trees don’t come back.

Modified forests

An important point made by Rawlence is that simply having more trees further north is not a solution to climate change.

“Although the boreal forest is the planet’s greatest source of oxygen, more trees there do not necessarily mean more carbon sequestered from the atmosphere,” he writes.

“As trees invade frozen tundra, they accelerate the melting of permafrost, frozen soils that contain enough greenhouse gases (GHGs) to accelerate global warming beyond anything scientists have modeled.”

The new northern forests and those that regrow after fires are not the same as the old forests; their structure is radically different. In Siberia, Scots pine replaces larch at burn sites, leading to a reduction in the carbon that forests can hold. Of the carbon dioxide that the taiga sequesters, the larch is responsible for absorbing 55%, even though less than 40% of the trees are larch.

This leads to a major hole in many models, which rely on fixed assumptions about how much carbon dioxide forests can store. However, “a warming forest is less efficient at carbon cycling and sequestration,” warns Rawlence, citing a study that indicates that by 2040, forests will absorb only half the amount of carbon dioxide. they are currently absorbing.

In some of the other changes he sees, the aggressive growth of trees in northern Scandinavia is putting reindeer herding at risk, because reindeer need old-growth forests that take 160 years to grow. Scots pines release their seeds earlier, disrupting the seasonal cycles of the forest. In Alaska, trees turn brown as warm air sucks moisture from their leaves.

Open Arctic

Chebakova predicts, as quoted by Rawlance, that by 2100 50% or more of Siberia’s forest will become steppe. The southern limit of forests will shift about 1,000 km to the north, making about 85% of Siberia suitable for agriculture.

Global warming is already opening up the Arctic economy. Among the developments listed by Rawlance are wind farms inside the Arctic Circle in Norway, the expansion of RusAgro wheat farms near Vladivostok and the opening of Arctic shipping routes.

At the same time, while large swathes of the Arctic are expected to become habitable for humans this century, the reverse is happening further south. By 2070, an estimated 3 billion people will live in areas where it will be too hot to work outside or sleep without air conditioning. A wave of emigration from the south to the north including in arctic regions is planned.

Cruel feedback loops

Many examples are emerging of what Rawlence calls “cruel feedback loops,” where a change precipitates new developments that accelerate the process of climate change.

Thus the blackening of the glaciers in Greenland leads them to absorb more heat and accelerates the melting. Another example is that Siberian rivers now discharge 15% more water into the Arctic Ocean than a decade ago, which in turn changes the salinity of the ocean.

And, as documented in the book, wildfires, a warmer climate, and the steady northward movement of forests are melting permafrost, which stores more carbon than humans have released since they started. to burn fossil fuels.

Angela C. Hale