Warmth in the Alps visible from space

The effects of warming the Alps are visible from space, according to a study by Lausanne and the University of Basel published Thursday in the journal Science. Plant productivity above the tree line has increased by more than 80% of the area.

The most notable change is a marked and general growth of plants at high altitudes in the Alps. This is the conclusion of a study conducted by Sabine Rumpoff of the University of Basel and a team of Antoine Guisan and Gregoire Marithos of the University of Lausanne.

Together with research groups based in the Netherlands and Finland, the scientists tested snow cover and vegetation changes using high-resolution satellite data collected from 1984 to 2021.

During this period, plant biomass grew above the tree line in more than 77% of the Alps. This phenomenon of ‘greening’ due to climate change has already been well documented in the Arc and is beginning to be identified in the mountains.

Plant biomass growth

“The scale of change in the Alps is enormous,” said Sabin Rampoff, the study’s first author, in a press release from the two organizations. The Alps are becoming greener, as vegetation colonizes new areas, becoming denser and higher. The event marked the highest at an altitude of about 2300 meters.

Previous studies have focused on the effects of warming on alpine biodiversity and changes in the distribution of plant species. To date, no one has conducted such a comprehensive analysis of the evolution of plant productivity in the Alps.

The authors point out that the growth of plant biomass is primarily responsible for changes in rainfall regimes and the prolongation of plant growth seasons, resulting in increased temperatures.

‘Alpine plants adapt to difficult conditions, but they are not very competitive,’ explains Sabine Rumpf. As environmental conditions change, these highly specialized species lose their edge and become more competitive. ‘The unique biodiversity of the Alps is therefore under considerable stress,’ the researchers note.

Snowpack slightly reduced

In contrast to vegetation, the amount of snow cover above the tree line has changed slightly since 1984. Experts have excluded areas, glaciers and forests below 1700 meters from their analysis: they have highlighted the fact that snow cover has decreased significantly in about 10 years. % Of remaining region.

It may sound moderate, but according to scientists, it is alarming. ‘Previous analysis of satellite data did not identify such a trend,’ commented Antoine Guisan. ‘This is probably due to insufficient resolution of the satellite images or because the periods considered are too short,’ he speculates.

Gregor Merithos added, “It’s been many years since local measurements on land showed a decrease in the thickness of snow cover at low altitudes.” As a result of this reduction, some areas are now largely deprived of snowfall.

Water cycle

This loss of snow cover is especially noticeable in places where, forty years ago, it was all year round, about 3000 meters above sea level. This has had an impact on the entire water cycle, Pre Rumpf told Keystone-ATS.

Some ecosystems are under pressure. Researchers have also noted the impact of drinking water supply in mountainous areas.

With warming, the Alps will become more or less white and more green, entering a vicious circle: ‘Green mountains mean less reflection of sunlight, which will further extend the warming’, concludes Sabine Rampoff.

/ ATS

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