IMPACTS OF GLACIER LOSS

Despite their extreme conditions, glacier-fed streams and areas near glacier fronts host rich ecosystems, including bacteria, fungi, algae, plants, and animals. These rivers support unique biodiversity adapted to cold, turbulent waters, where macroinvertebrates thrive and form the foundation of the food chain. Feeding fish (when present), birds, and amphibians, these organisms also keep the waters clean by consuming algae and organic matter. Glacial rivers don’t just support local biodiversity; they nourish entire downstream networks, impacting ecosystems from mountain streams to the sea.

As glaciers shrink, the loss of glacial runoff in mountain streams leads to habitat changes that attract more generalist species from downstream, increasing local biodiversity. However, this shift threatens specialized species that rely on glacial conditions, reducing overall biodiversity across river networks. While some generalist species thrive, unique glacial species struggle, leading to a more uniform but less diverse ecosystem.

Glaciers play a major role in the water cycle, particularly in the catchments of glacier-fed rivers such as the Rhône River. Glacier retreat firstly leads to an increase in glacier runoff, and thus to higher annual flows in glacier-fed rivers, mainly in summer. However, when the ice volume becomes too small, the annual glacier runoff reaches a maximum (sometimes called “peak water”), beyond which runoff steadily declines. As a result, river flows downstream tends to be more precipitation-dependent, more variable and less predictable over time.