Avalanches are changing in the Pyrenees: smaller, but more frequent and closer to people

In the Aragonese Pyrenees , where snow dictates the rhythm of winter and a significant part of the economy, 
avalanches are changing their behavior. They are no longer just the large avalanches that once descended to the valley floor only occasionally; now they are smaller , but also more frequent and, above all, closer to paths, roads, and other busy areas. This is the warning issued in a recent scientific study , which highlights a trend that is causing concern among both researchers and land managers.

The warning comes at a critical time. After a particularly harsh winter , with at least eight deaths in the Pyrenees, the scientific community is warning that the risk is not disappearing, but rather transforming. New patterns, linked to climate variability, paint a picture in which avalanches can more easily catch mountaineers, skiers, or key infrastructure by surprise in valleys like Canfranc.

They have studied 57 documented episodes between 1910 and 2014

The data comes from the work of five scientists published in the journal Cold Regions Science and Technology, which concludes that avalanches in the Pyrenees are becoming smaller but more frequent. The analysis focused on 57 documented events between 1910 and 2014 in the Canfranc Valley, where a direct relationship was identified between climate variability, determined in part by the North Atlantic Oscillation (NAO), and the probability of avalanches.

The study is part of the European project Pyrenées4clima, which brings together seven Pyrenean regions (Andorra, Aragon , Catalonia, the Basque Country, Navarre, New Aquitaine, and Occitanie) under the coordination of the Pyrenean Climate Change Observatory (OPCC-CTP). It is based on the premise that the Pyrenees are among the mountain areas with the highest avalanche activity in the world.

The work is signed by five experts: Jaime Boyano Galiano, Alberto Muñoz Torrero, Juan Antonio Ballesteros Cánovas, all three from the National Museum of Natural Sciences (MNCN-CISC); Juan Ignacio López Moreno, from the Pyrenean Institute of Ecology (IPE-CISC), and Osvaldo Franco-Ramos , from the Institute of Geography of the National Autonomous University of Mexico.

More common avalanches in the second half of the 20th century

The research provides key data for improving risk assessment in mountain environments affected by climate change. Specifically , 57 avalanche events have been reconstructed—30 in Estiviellas and 27 in Rinconada—using historical records, tree-ring analysis, geomorphological mapping, and meteorological data. The results show that large avalanches were more common in the second half of the 20th century, while in recent decades smaller but more frequent events, concentrated at higher elevations, have predominated.

The study also highlights the reforestation policies and protective infrastructure developed since the beginning of the 20th century, which have helped reduce the severity of large avalanches. However, experts warn that the increase in smaller avalanches could put these defense systems to the test.

Juan Antonio Ballesteros , one of the five signatories of the study, explains how they have verified the trend that “less frequent avalanches, located in the highest parts , are becoming more frequent, and can affect the safeguard infrastructures that serve, precisely, to mitigate the effects of large avalanches.”

CLIMATE CHANGE ADDS UNCERTAINTY

Researchers agree that climate change is behind this trend. “It creates more variable and extreme conditions ,” explains Ballesteros, who points out that rising temperatures and irregular rainfall make the snowpack more unstable, especially at the end of winter. This increases the risk for sports and professional activities in the mountains.

Similarly, the OPCC emphasizes that more complete data series are still lacking for certain altitudes in the Pyrenees, making it difficult to establish definitive statistical trends . Even so, there is a consensus that climate change is altering the frequency, type, and timing of avalanches.

The scenario is clear: less snow at lower elevations, but greater instability at higher altitudes. This implies fewer events in lower areas, but more uncertainty and an increase in wet avalanches at higher elevations, with more unpredictable behavior.

MORE DATA TO ANTICIPATE RISK

The Pyrenees4clima project is also promoting new lines of work, such as the creation of more comprehensive databases on snow depths and the updating of climate projections for the Pyrenees. The goal is to improve the ability to anticipate these phenomena.

The agencies involved in the safety of border crossings, such as Portalet and Bielsa-Aragnouet , emphasize the importance of sharing snow and weather data among government agencies, emergency services, and infrastructure managers. Analyzing each avalanche “almost like an autopsy ,” experts point out, will allow them to “learn from its causes and consequences.” This knowledge, they conclude, will be key to adapting the Pyrenees to a future in which snow will continue to play a central role, but will become increasingly unpredictable.