Melting alpine glaciers in the Swiss Alps are transforming high-altitude ecosystems and increasing disease transmission among bees. A study led by the University of Lausanne reveals that as pioneer plants vanish, wild bees and honeybees share the same floral resources, spreading pathogens from managed hives into vulnerable wild populations.
Swiss glaciers are retreating at a record pace, fundamentally altering the alpine landscape. While the loss of ice directly threatens long-term water supplies and human survival, researchers have uncovered a less visible ecological consequence: the proliferation of diseases among both wild and managed bee populations in the Swiss canton of Valais.
How Receding Glaciers Alter Alpine Plant Communities
As ice cover disappears, newly exposed terrain is progressively colonized by plants and associated organisms. Over time, this vegetation shifts significantly. Pioneer species that provide vital floral resources for native pollinators begin to grow scarce while other plants become more abundant.
Normally, honeybees and wild bees avoid competing directly for food. Different species specialize in distinct plants, creating a natural division of labor that minimizes physical contact and lowers the risk of pathogen transmission. The ongoing glacial retreat disrupts this balance. As specific floral resources disappear, both groups increasingly visit the same remaining blossoms.
Pathogen Transmission at the Mont-Miné Glacier
To investigate the phenomenon, researchers from the University of Lausanne, the University of Milan, and the Italian Council for Agricultural Research and Economics analyzed bee populations near the Mont-Miné glacier in the Val d’Hérens. The scientific team focused on five specific pathogens: three viruses and two parasites.
The study examined the deformed wing virus, which is closely linked to varroa mite infestations and ranks among the leading causes of colony loss. Investigators also tracked the acute bee paralysis virus, the chronic bee paralysis virus, the microsporidian parasite Nosema ceranae, and the single-celled intestinal parasite Lotmaria passim.
In areas freshly freed from ice, scientists detected all five pathogens in domestic honeybees, while wild bees in those same young zones carried only two of the infections. In older ice-free zones where the vegetation has had years to evolve, the distribution changed completely. The presence of the deformed wing virus rose significantly among wild bees, demonstrating that pathogens jump more readily between populations as shared habitat matures.
In general, honeybees focus on certain plant species that are rarely visited by wild bees, which reduces opportunities for contact and thus for the transmission of pathogens. University of Lausanne and University of Milan, via rts.ch
Ecosystem Interactions and Future Research
Flowers serve as transmission hubs in this changing environment. When an infected forager leaves infectious particles behind on a blossom, subsequent visitors can easily pick up the disease. This overlap in resource use accelerates as plant communities adapt.
The findings illuminate a subtle aspect of environmental degradation. Climate change alters the entire ecosystem developing in the wake of glacial retreat, restructuring the intricate network of interactions among native organisms.
Understanding these processes is crucial to developing effective strategies for the protection of pollinators and the ecosystem services they provide. Gianalberto Losapio, co-author of the study, via watson.ch
The research team plans to replicate these observations across other glacier-impacted regions featuring varying densities of managed and wild bee colonies.
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