The Tibetan plateau, the earth’s highest and largest plateau, sometimes called the “Roof of the World,” and its immediately surrounding mountains contain the greatest diversity of bumblebee species in the globe. But, these little-studied populations may be threatened by climate change, new research shows. A paper, entitled “Bumblebees, climate and glaciers across the Tibetan plateau (Apidae: Bombus Latreille),” published in the journal Systematics and Biodiversity in January, finds that if the many of glaciers in the Tibetan plateau melt without replenishing, they could dry up the summer streams that nourish the plants and flowers on which many of these bumblebees rely for food. It’s the first time glacier melt has been identified as a potential threat to bumblebees, even as scientists around the world race to understand recent declines in bumblebee populations and to devise strategies to revive them.
The research was conducted by scientists from China and London, who set out to understand the relationship between climate and bee species diversity in the Tibetan plateau. The researchers defined the Tibetan plateau broadly to include portions of China, Nepal, Bhutan, India, and Pakistan, a region about one third the size of the United States. To understand regional species variations, they collected data on the various species found and mapped them across the region. They then analyzed climate variables against variation in bee species composition.
The researchers discovered that the richness of the social bumblebee species in the alpine zone of the Qinghai-Tibetan Plateau is greater than that of any other alpine region of the world. The area contains 44 species—by comparison, all of South America holds 24 species. Further, they found three principal groups of fauna, which can be distinguished by their constituent species: the Himalayan fauna of the south with many endemic species, fauna of the east in the Oriental region, and Palaearctic fauna of the north.
The research team, led by Paul Williams, was also able to find some distinct relationships between the types of bees populating an area and climate variables. The primary factor linked to bee variation was differences in precipitation across the region, which divided the study area into two parts— the dry west and north and the wetter east and south.
When finalizing the data, there was one thing the researchers couldn’t figure out: why were bee populations so robust in the arid northern and western areas, such as Ladakh and Zanskar, contrary to what was expected due to the aridity in these areas? According to the study, “these small western and northern ‘oases’ appear to be strongly dependent on narrowly localized irrigation by continuous summer streams…often fed by meltwater from permanent glaciers.” However, these glaciers are believed to be melting rapidly due to climate change, the researchers note. Therefore, the rapid melt of the glaciers is a potentially serious conservation concern for the bumblebee species that thrive in these areas.
The impact of melting glaciers on bee populations most directly relates to the bee fauna in the north and west of the Tibetan Plateau; however, this connection could have impacts for populations across the region. The researchers conclude, “interruption of stream flow could result in sudden, complete and permanent collapse of bumblebee populations throughout these valleys.” This ecological disruption could affect ecosystems in unknown and irreversible ways.
Further, the decline of bee species in any part of the globe is significant because bees are one of the most hardworking, irreplaceable species on the planet. According to Marla Spivak, American entomologist and MacArthur Fellow, over one third of the world’s crops are dependent on bee pollination. In the recent decades, bumblebee populations have faced many perils due to habitat loss, pathogens, and pesticides. Yet, this research is the first time glacier melt has been identified as a conservation issue for bees. In this way, this unique paper points to the complex and delicate life systems that are affected by glaciers.
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