The famous snow-capped peaks of the Alps are rapidly fading and being replaced by vegetation cover – a process called ‘greening’ which is expected to accelerate climate changeaccording to a study Thursday.
The research, published in Sciencewas based on 38 years of satellite imagery across the entire iconic European mountain range.
“Honestly, we were very surprised to see such a greening trend,” first author Sabine Rumpf, an ecologist at the University of Basel, told AFP.
Greening is a well-known phenomenon in the Arctic, but so far little implemented on a large scale in mountainous areas.
However, since the poles and mountains are is warming faster than the rest of the planetthe researchers suspected comparable effects.
For their analysis, the team looked at regions 1,700 meters (5,600 feet) above sea level, to exclude areas used for agriculture. They also excluded forested areas and glaciers.
According to the results, which covered the period 1984-2021, snow cover was no longer present in summer over nearly 10% of the study area.
Rumpf pointed out that satellite images can only verify the presence or absence of snow – but the primary effect of warming is to reduce the thickness of the snowpack, which cannot be seen from space.
Second, the researchers compared the amount of vegetation using wavelength analysis to detect the amount of chlorophyll present and found that plant growth increased over 77% of the area studied.
Greening occurs in three different ways: plants begin to grow in areas where they were not present before, they grow taller and more densely due to favorable conditions, and finally particular species normally grow at higher altitudes. lows move to higher areas.
“It’s climate change that’s driving these changes,” Rumpf said.
“Warming means we have longer growing seasons, we have more benign conditions that favor plant growth, so plants can just grow bigger and faster,” she added.
The effect is additive: “The warmer it is, the more precipitation falls as rain rather than snow.”
And there are several negative consequences.
First, much drinking water comes from melting snow. If the water is not stored as snow, it disappears faster via rivers.
Then, the habitat of species adapted specifically to the alpine environment is disrupted.
The disappearance of snow is also hurting the tourism industry, a key economic driver for the region.
“What we tend to forget are the emotional aspects of these processes that the Alps are like a very iconic symbol and when people think of Switzerland it’s usually the Alps they think of,” Rumpf pointed out. .
While alpine greening could increase carbon sequestration, feedback loops are more likely to cause amplified warming and permafrost thaw, the researchers say.
Snow reflects about 90% of solar radiation, vegetation absorbs much more and returns the energy as heat, further accelerating warming, snowmelt and more vegetation: a vicious circle.
From green to brown?
The future of the Alps cannot be predicted with certainty.
“In terms of snow, it’s pretty straightforward,” Rumpf said. “I would expect the snow cover to disappear more and more, especially at lower elevations.”
So far, another phenomenon known as “browning” – in which the ground is no longer covered by snow or vegetation – has only been detected in less than one percent of the area surveyed. .
This is much less than what has been observed in the Arctic, or in the mountains of Central Asia.
It is fueled by two factors: an increase in extreme rainfall events followed by droughts, and a reduction in water available to plants that has been produced by annual snowmelt.
“We don’t know for the future whether browning is going to happen more and more,” concluded Rumpf, who hopes to repeat the observations in a few years.
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