Between Refuge and Risk: The Avalanche Paradox for Mountain Ungulates
ESP version ITA version In the changing context of mountain environments, climate change manifests with rapid and significant transformations, profoundly influencing sensitive communities and ecological processes. A crucial element in this landscape is represented by the seasonal conditions of snow, which prove to be determinants for the dynamics of mountain ungulate populations. These variations directly affect vital ecological and physiological aspects, such as the energy costs of locomotion, vulnerability to predation, and the availability and quality of forage, both in summer and winter.
A recent study published in Nature explored how mountain goats, adapted to steep terrains to evade predators, paradoxically find themselves at risk due to the frequent instability of these slopes, which can generate avalanches. The research, conducted in southeastern Alaska on 421 goats monitored for 17 years, highlights that avalanches cause between 23% to 65% of annual deaths, primarily affecting the young and small. These steep areas, chosen to mitigate the risk of predation, turn out to be ecological traps due to their high risk of avalanches. This risk is variable, with peaks during the most unstable months for snow, especially at the beginning of winter and during the spring thaw.
The migratory and wintering strategies of ungulates further influence their exposure to the risk of avalanches. For example, mountain goats in Lynn Canal are extremely migratory, moving to low-altitude forested habitats during the winter, while other populations remain at higher altitudes, exposing themselves more to danger.
Climate change exacerbates this dynamic, modifying the frequency and intensity of avalanches, and consequently, the spatial and temporal distribution of these lethal events. Forecasts indicate an increase in wet avalanches compared to those of dry snow, with a potential increase in avalanche mortality rates.
The persistence of this risk in mountain systems, combined with the anticipated rise in the snowline elevation, may reduce the avalanche danger at lower altitudes, but the risk will continue to be a significant component in the ecology of mountain ungulates. However, the demographic influence of avalanches on ungulate populations is likely to persist in the future because both the avalanche danger and the ranges of mountain ungulates are expected to shift upward as the climate warms.
It is essential to emphasize that the growth rates of mountain goat populations are particularly low and can only sustain limited annual removals. Therefore, avalanche mortality, especially among young individuals, can have severe demographic impacts, leading to population decline. These data highlight the need to reconsider conservation and management strategies for these vulnerable populations.
The intensification of climate change and its extreme manifestations, such as avalanches, necessitates a rethinking of conservation policies to protect not only mountain ungulates but also the ecological integrity of mountain environments, which are crucial for global biodiversity.
Source: https://www.nature.com/articles/s42003-024-06073-0
Credits picture: NPS/Diane Renkin
