A study conducted in the Swiss Alps by the University of Lausanne and the University of Milan shows that glacier retreat and the changing vegetation could influence the spread of certain pathogens between honeybees and wild bees.
The retreat of glaciers leaves behind areas that are gradually colonised by plants and their associated organisms. Over time, plant communities change: some species become more abundant, while pioneer species that provide key floral resources for pollinators become scarcer. These changes could alter how different bee species use the available floral resources, potentially increasing the overlap in their resource use and hence the likelihood of pathogen transmission. This is the finding of a study published in Oikos , conducted by scientists from the University of Lausanne, the University of Milan, and the Council for Agricultural Research and Economics.
The researchers investigated five pathogens—three viruses and two parasites—and examined their presence in wild and honeybee populations in the Mont Miné glacier foreland, Valais region.
Their results show that all five pathogens were detected in honeybees in recently deglaciated areas, whereas wild bees were affected by only two of the five. The picture was different in older areas, where the prevalence of deformed wing virus (DWV), more commonly associated with honeybees, increased markedly among wild bees too.
Flowers as potential transmission points
This difference may be explained by the way pollinators use floral resources. Honeybees generally concentrate on certain plant species that are less frequently visited by wild bees, reducing opportunities for contact and, consequently, pathogen transmission. The researchers predict, however, that as glaciers continue to retreat and key floral resources become scarcer, bees may have fewer options and increasingly rely on the same resources. Flowers can act as points of pathogen transmission: infectious particles deposited by infected bees can subsequently be picked up by other individuals.
A lesser-known consequence of climate change
These findings highlight a less visible consequence of climate change. Glacier retreat does not simply mean that ice disappears and there is less water for hydropower; it progressively reshapes the entire ecosystem that develops in its wake and the underlying complex network of interactions among organisms.
The researchers now call for these observations to be replicated in other areas affected by glacier retreat and under different bee densities in order to better understand how changing mountain landscapes may affect pollinator health. "Understanding these processes is essential for developing effective strategies to conserve pollinators and the ecosystem services they provide," says Gianalberto Losapio, co-author of the study and a researcher at the University of Lausanne's Faculty of Geosciences and Environment and at the University of Milan. "Further studies will help us better understand the link between the structure of plant–pollinator networks and pathogen transmission among different bee species."
Source: A. Ferrari, G. Cilia, M. Conti, B. Ngan Tu, N. Khelidj, G. Losapio, C. Polidori, Unshared on the top: strong segregation of pathogen communities between western honey bees and wild bees in a retreating glacier foreland , Oikos, 2026
