The Siberian tundra could disappear by the year 2500 if greenhouse gas emissions are not drastically reduced.
Even at best, two-thirds of this landscape – defined by its short growing season and cover of grasses, moss, shrubs and lichen – could disappear, leaving two fragments 2,500 kilometers apart, scientists recently predicted. And if the tundra’s permafrost melts, vast amounts of stored material could be released greenhouse gases into the atmosphere and potentially accelerate global warming.
“It was overwhelming for us to see how quickly the tundra is being transformed into forest,” said the ecologist and forest modeler Stefan Kruse from the Alfred Wegener Institute (AWI) Helmholtz Center for Polar and Marine Research in Bremerhaven. Not only will the loss of the tundra deal a blow to biodiversity and human culture, but it could also worsen Arctic warming, Kruse told Live Science.
Related: Is climate change making the weather worse?
warming in Arctic has been developing rapidly in recent decades, about twice as fast as warming in the rest of the world. Between 1960 and 2019, air temperatures in the Arctic increased by almost 7.2 degrees Fahrenheit (4 degrees Celsius). according to the National Snow and Ice Data Center (opens in new tab) (NSIDC). This heat reduced sea ice coverage and is also affecting the land of the Arctic. One such impact is the northward advance of Siberian larch forests.
How quickly these forests will replace the grassy, shrubby tundra ecosystem is unknown. Tree line changes in response to climate are not uniform across the world, Kruse said. In some areas, tree lines have advanced northward. In others they have remained static; in yet others they have even withdrawn. Previous research on the Siberian tundra has focused on small areas, but there can be large variations from place to place.
Kruse and his colleague, AWI professor Ulrike Herzschuh, have now created a new computer model that evaluates the entire 4,000-kilometer stretch of the Siberian tundra. The model takes into account the life cycles of individual trees: from how far they can spread their seeds, to how well they grow in competition with other trees, to growth rates based on temperaturePrecipitation and Depth of Summer Thawing of permafrost occurring in tundra regions.
The researchers found that once the trees march north in response to warming, they do so quickly — and they’re unlikely to retreat again when temperatures cool. Under a scenario where carbon If emissions are reduced to zero by 2100 and global temperature rise remains below 2 degrees C (3.6 degrees F), only 32.7% of today’s tundra would remain by 2500. This fraction would be split into two mini-tundras: one at Chukotka in the far east and one on the Taymyr Peninsula in the far north.
cascade of change
But even this dire scenario may be impossible to achieve without very quick action, meaning the outcome for the Tundra could easily be far worse. In an intermediate scenario, where carbon emissions do not decline until 2050 and are cut in half by 2100, larch trees would cover all but 5.7% of today’s tundra by 2500, essentially wiping out the ecosystem.
In the warmer global scenarios, trees could spread north by as much as 18.6 miles (30 km), the researchers reported May 24 in the journal eLife (opens in new tab). When Kruse and Herzschuh tested what would happen if temperatures cooled after the tundra became a forest, they found that the tree line was not retreating as fast as it had been advancing. Once mature trees are in place, they can take a beating, Kruse said.
Related: When did scientists first warn humanity about climate change?
The study does not directly model what might happen to tundra residents, such as reindeer, Kruse said, but splitting populations into two regions where they’re cut off from mixing is usually bad for species survival. Reindeer (known as caribou in North America) migrate north to south and back again year-round, and it is unknown how forest extent may affect their migration and life cycle.
The effects will likely be felt by humans as well. Indigenous cultures like the Nenets of north-western Siberia herd and hunt reindeer.
“The culture is partially dependent on the tundra,” Kruse said. “If that is lost, it will be a great loss to humanity.”
How the loss of the tundra will affect future warming is also uncertain, but covering the mossy, scrubby meadows with tall trees could make matters worse. Snow-covered tundra is lighter in color than larch forest canopy; The forests will therefore absorb more heat than the tundra, potentially making the Arctic hotter at a faster rate, Kruse said. That extra heat could accelerate and deepen the melting of the tundra’s permafrost, which stores vast amounts of greenhouse gases — up to 1,400 gigatons worldwide, the researchers said NSIDC (opens in new tab). The thawing of the permafrost could also release these gases long-frozen microbes and viruses.
The change will likely go beyond replacing the tundra with larches, Kruse added. When warmer summers thaw deeper and deeper layers of permafrost, evergreen trees can also move in. These trees stay covered in leaves all year round and may absorb even more heat than larches. The southern side of the taiga, where temperatures are already warmer than the north, is likely to heat up even more, leading to droughts and wildfires — which release even more carbon into the atmosphere.
The results provide compelling reasons to push for ambitious reductions in emissions from fossil fuels. However, the model used in the study could also be used to identify the most resilient parts of the Siberian tundra, Kruse said. These resilient areas could be prioritized for conservation investments.
“The best option would be to reduce global greenhouse gas emissions to ease the pressure,” he said. “But still, if we can’t do that, we have to protect species.”
Originally published on Live Science
https://www.livescience.com/vanishing-siberian-tundra Siberian tundra could vanish in less than 500 years