Due to climate change, larch forests threaten to advance at a speed of 30 kilometers per decade. And that could end the Siberian tundra by the middle of this millennium.

And with that we will not only lose the still extensive tundra, but also the unique plants and animals that (sometimes only) occur there. Researchers warn about this in the magazine eLife†

Fast heating

It is no secret that the Arctic is warming at lightning speed. In the past 50 years, the temperature has risen by about 2 degrees Celsius, which means that the warming here is faster than ever. And you see that too; for example, Arctic sea ice is languishing before our very eyes. But it doesn’t stop there, says researcher Ulrike Herzschuh. “The environment on land will also change drastically.”

Tundra

He is thinking in particular of the still extensive tundra in Siberia and North America. The unique ecosystem is doomed to lose considerable ground in the coming decades. “That’s because the tree line (the boundary of a habitat to where trees can grow, ed.), which is already changing slowly, will shift rapidly northwards in the near future. In the worst-case scenario, there will be virtually no tundra left by the middle of this millennium.” Herzschuh and colleagues draw that conclusion after simulating the future of the tundra in northeastern Russia. “The main question on our minds was: what emission path should humanity follow in order to preserve the tundra as a refuge for flora and fauna and continue to play a role in the cultures of indigenous peoples?”

LAVESIA

For their simulations, the researchers used a model called LAVESI, which uniquely approximates treeline shifting. “What makes LAVESI unique is that it allows us to simulate the entire treeline at the level of individual trees,” explains researcher Stefan Kruse. “The model describes the full life cycle of Siberian larch trees in the transition zone to tundra: from seed production and distribution to germination and mature trees. In this way we can realistically simulate the advancing tree line in a warmer climate.”

And that’s exactly what the researchers did. They based the model on various climate scenarios, including one in which very ambitious climate goals are embraced that result in the global temperature remaining below 2 degrees Celsius at least until 2100. But climate scenarios were also simulated in which significantly less or even nothing was done to combat global warming.

smaller

The results are sobering. For example, the simulations show that larch trees can rush northwards at a speed of up to 30 kilometers per decade. And with that they penetrate the tundra at lightning speed. Unlike those larch trees, that tundra cannot expand northwards, because that’s where the Arctic Ocean lies. And so the tundra is doomed to shrink. And not just a little bit; in the bulk of simulated scenarios, by the middle of this millennium, only 6 percent of the still mighty Siberian tundra remains. In that scenario, the Siberian tundra no longer forms a continuous ecosystem, but splits into two tundras that are about 2,500 kilometers apart. Many of the changes the tundra undergoes in these scenarios are final; even if the climate cools down a bit over the millennium, the larch forests will not fully retreat and so the tundra will never be as extensive as it once was.

Heap

There was a glimmer of hope when researchers simulated a situation in which we make ambitious climate goals a reality. In that scenario, about 30 percent of the Siberian tundra could be saved. But in that case, too, the tundra will no longer form a continuous area, but will split into two areas, which are far apart. And while those two areas may be somewhat larger than in the scenario where we’re pursuing less ambitious climate goals, that’s still bad news for the plants and animals that remain in these areas. “The diversity in these fragments of tundra some 2,500 kilometers apart is threatened by the fundamental disadvantages that a small population has – think of inbreeding or genetic drift,” the researchers write in their research article†

Harsh measures are therefore needed to save the Siberian tundra and the unique species that live there from their demise. “Because one thing is clear,” says Eva Klebelsberg, affiliated with the World Wildlife Fund, in response to the research. “If we continue like this, the ecosystem will gradually disappear.”