As Siberia continues to warm, is the disappearance of the tundra inevitable?

Siberian tundra could disappear within 500 years?

By the year 2500, this iconic landscape may no longer exist.

View image of The tundra is melting as a result of climate change. (Credit: JONATHAN NACKSTRAND /AFP/Getty Images)

By the middle of this century, the Siberian tundra could disappear completely from the Earth, and this situation will be difficult to improve unless greenhouse gas emissions are significantly reduced.

Covered by meadows, mosses, shrubs and lichens, the growing season of the tundra is very short. According to scholars' predictions, even in the best case scenario, two-thirds of the tundra landscape will completely disappear from people's sight, and the complete permafrost will be reduced to two parts 1,553 miles (2,500 kilometers) apart. In addition, as the permafrost of the tundra melts, a large amount of greenhouse gases stored in it will enter the atmosphere, which may further aggravate global warming.

"Tundra will be replaced by forest at an alarming rate," ecologist and forest modeler Stefan Kruse from the Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, told Live Science. He said the disappearance of the tundra would not only be a loss for biodiversity and human civilization, but it could also exacerbate climate warming in the Arctic.

The Arctic has warmed significantly in recent decades, at about twice the rate of the rest of the world. From 1960 to 2019, temperatures across the Arctic rose by nearly 7.2 degrees Fahrenheit (4 degrees Celsius), according to the National Snow and Ice Data Center (NSIDC). The warming has led to a reduction in sea ice cover, which has had an impact on the Arctic continent, one consequence of which is the northward shift of Siberian larch forests.

How quickly forests will replace meadows and shrubs in tundra ecosystems is still unclear. Cruz pointed out that tree lines are not responding to climate change uniformly around the world. In some areas, tree lines are moving north, in others they are staying the same, and in some areas, they are even moving back. Most previous studies of the Siberian tundra have been conducted on a small scale, but the situation will be different depending on the geographical location.

Crews and his colleague Professor Ulrike Herzschuh, also from the Alfred Wegener Institute (AWI), have now created a computer model that comprehensively assesses the 2,485-mile (4,000-kilometer) Siberian plain. The model takes into account the life cycle of each tree: from how far a tree's seeds can spread, to its ability to grow in competition with other trees, to its growth rate based on temperature, precipitation, and the summer thawing of permafrost in the tundra.

The study shows that once the tree line moves northward due to climate warming, the process will be very fast, and even if the temperature drops, the forest is unlikely to retreat south again. If carbon emissions are reduced to zero in 2100 and global warming is controlled within 3.6 degrees Fahrenheit (about 2 degrees Celsius), under this assumption, by 2500, only 32.7% of the Siberian tundra landscape can be preserved, forming two "mini tundras" located in Chukotka in the Far East and Taimyr Peninsula in the Far North.

chain reaction

However, if no immediate action is taken, the future of the Siberian tundra will be far bleaker than the above scenario. In a more realistic scenario, carbon emissions do not begin to decline until 2050. If carbon emissions can be reduced by half by 2100, by 2500, the Siberian tundra landscape will shrink to 5.7% of its current size, and larch will cover it, and the original ecosystem will die.

Scholars have reported in the journal eLIFE that under a warmer global climate, the treeline could move up to 18.6 miles (30 kilometers) north. What happens if the temperature drops again after the forest replaces the tundra? Cruise and Herschitz tested this and found that the treeline does not retreat as quickly as it initially moved north. Cruise said that once a forest matures, it has strong vitality.

According to Cruise, the study did not directly simulate the impact on tundra creatures, such as reindeer. However, as the tundra is split in two, the possibility of hybridization will be cut off, which is a test for species survival. Reindeer (i.e., North American caribou) migrate from north to south and then back north every year. No one has yet been able to answer how the expansion of the forest will affect their migration and how it will change the way this species survives.

The loss of the tundra could also have specific consequences for humans, such as the Nenets, an indigenous culture that lives in northwestern Siberia and survives on herding and reindeer hunting. “This culture is partly dependent on the tundra,” Crews said, “and its loss would be a significant loss for human civilization.”

It also remains to be seen what effect the loss of tundra will have on future global warming. In theory, towering trees replacing mosses and shrubs in meadows could make the situation worse. Because the snowy tundra has a lighter color than the larch canopy, the forest would absorb more heat than the tundra, making the Arctic warmer at a faster rate, Crews said. This extra heat could accelerate the melting of tundra permafrost and intensify the thawing of deep permafrost, releasing up to 1.4 trillion tons of greenhouse gases stored there, as well as microorganisms and viruses that were previously frozen for a long time, according to the National Snow and Ice Data Center (NSIDC).

It’s not just the larch forests that may be replacing the tundra, Crews added. As hotter summers cause the permafrost to thaw deeper and deeper, evergreen trees will gradually move into the tundra, where their year-round green leaves will absorb more heat than the larch forests. Temperatures south of the coniferous forests are already higher than in the north, so this will increase temperatures further, leading to droughts and wildfires, sending more carbon emissions into the atmosphere.

The findings make a compelling case for pushing for stricter plans to cut fossil fuel emissions, and the model used in the study could also be used to pinpoint the most resilient areas of the Siberian tundra, which Crews says could be prioritized for conservation investments.

"The best option would be to reduce greenhouse gas emissions worldwide, thereby reducing pressure on the tundra," Crews said. "If that is not possible, then conservation efforts are necessary anyway."

BY:Stephanie Pappas

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