High in Europe’s mountains, a surprising transformation is underway. Using 40 years of satellite data, Choler and colleagues discovered that spots where snow once lingered late into summer are becoming unexpectedly green. By tracking snow patterns and plant growth across the Alps, Pyrenees, and Greater Caucasus, they found these former snowfields are now hotspots of plant growth, raising questions about the future of unique mountain ecosystems that depend on long-lasting snow.
The team found that forty years, mountain snow is melting almost two weeks earlier than it used to. The scientists measured a shift of about 13 days earlier compared to the 1980s. Most mountain areas above the treeline (about 80%) are getting greener, with one-fifth showing dramatic increases in plant growth of more than 20%.
The biggest changes are happening in surprising places – rocky slopes facing north that used to be nearly bare of plants because snow stayed there so long. The extra warmth, almost a degree centigrade on average in July, and earlier snow melt has a bigger effect in these spots than the general rise in temperature.
Choler and colleagues tracked mountain changes by analysing thousands of satellite images showing snow cover and plant growth. They studied temperature records to calculate how much extra warmth plants received due to earlier snow melt. On the ground, they examined over 9,000 plots of mountain vegetation to identify which plant communities were changing most. This combination of space-view and ground-level data gave them a complete picture of mountain transformations.
Scientists already knew that snow cover was shrinking across the Northern Hemisphere due to climate change, but couldn’t explain why some mountain areas were getting much greener than others. This study reveals that late-melting snowfields are key to these patterns. As these snow patches vanish, they’re creating new opportunities for plants to grow in places that were too harsh before, which could lead to new mountain ecosystems, which is a concern when they’re already refuges for some specialised mountain species.
Choler P., Bayle A., Fort N. & Gascoin S. 2024. Waning snowfields have transformed into hotspots of greening within the alpine zone. Nature Climate Change. https://doi.org/10.1038/s41558-024-02177-x ($)
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