Hikers who try to summit Aneto, the 3,404-meter roof of the Pyrenees, witness the fragility of its glacier, which retreats year after year. It was in 2022 when Montaña Segura, the initiative promoted by the Government of Aragon and the Aragonese Mountain Federation, recommended for the first time that those who intended to climb Aneto do so by an alternative route to the classic one, through the Salterillo lake, to avoid dangerous situations in Los Portillones as much as possible, where fossil ice limits safe progress on the way to the summit. The situation has been repeated and the people who, in recent months, have ascended this mountain have verified the unstoppable retreat of the glacier, specifically in 2026 it is estimated that about two meters of thickness will have been lost, as confirmed by Ignacio López-Moreno, researcher at the Pyrenean Institute of Ecology, thanks to measurements made at the end of summer.
López-Moreno specifies that, in the past two decades, the loss was one meter annually, although in 2022 and 2023 the loss exceeded three meters. “The thickness of the glacier ice is about twelve meters on average, according to the most recent data, although there are small areas where it exceeds 20 and others two,” he details.
As in 2022, 2023 and 2025, in 2026, Montaña Segura has suggested using the Salterillo route, instead of the Portillones route, where "even with progression material you cannot travel safely because the crampons do not dig into the black ice, which is extremely hard, in addition to the risk of falling stones," indicates the person responsible for this program, Marta Ferrer.
Along the Salterillo itinerary, it was also recommended to use crampons and ice axes, until the end of August, when the final stretch was practically ice-free, notes the veteran Benasque valley guide Chemary Carrera. However, Montaña Segura, given the influx of people with little or no experience, who become disoriented and go off the itinerary, suggests that safety equipment continue to be carried as a precaution with the aim of reducing the risk of accidents.
Ixeia Vidaller, mountain guide and geologist, recalls the data contained in an article she co-signed with other researchers, “Evolution of the Aneto glacier between 1981 and 2022: ice loss observed through photogrammetry of historical aerial images and remote sensing techniques”, published in August 2023 in the magazine The Cryosphere, which refers to the fact that in the last 41 years “the total glacierized area has decreased by 64.7% and the thickness of the ice, on average, 30.5 meters.”
The retreat of glaciers is a phenomenon that drastically affects the entire Pyrenees and many other mountain ranges, due to the impact of global warming. Vidaller comments that the use of drones that generate high-resolution topographic maps allows year after year to compare the surface and thickness of the ice of this and other glaciers.
López-Moreno points out that another indicator that shows the fragility of the glaciers that remain in the Pyrenees is the low mobility of their ice. “He barely moves, he is in an extreme situation,” he adds.
In the Pyrenees or the Alps, the accelerated thaw and degradation of permafrost cause situations of instability in the rock walls, which forces mountain routes to be modified or temporarily closed, as happened this August on the classic Mont Blanc route through Gouter, in France. The new scenario invites us to keep security measures in mind.
