Bumblebees are moving up and that’s not a good thing

November 17th, 2020
Bombus gerstaeckeri (male) seen visiting its host plant, Aconitum napellus, showed considerable increase in elevation range. Photo © Nicolas J. Vereecken.

As the climate warms, plants that thrive at cooler temperatures are increasingly moving uphill. Their pollinators move up as well - if they succeed, at least. Researchers at Naturalis Biodiversity Center in the Netherlands compared their findings from the field with a study from 1889, and are concerned about species ‘falling off the top of the mountain’.

Volg onze verhalen

Bij Naturalis zijn we dag en nacht bezig om de collectie aan te vullen als rijksmuseum, academisch onderzoeksinstituut en erfgoedinstelling.

FacebookTwitterInstagramYouTube

Dusty
datasets

In 1889, biologist Julius MacLeod studied plants and bumblebees in the Pyrenees. Ecologist Koos Biesmeijer from Naturalis dug up the old dataset and did fieldwork to see what the situation was like more than a hundred years later. Such long-term biodiversity studies are crucial to chart the effects of climate change. "It shows nicely that there are probably many datasets gathering dust in drawers and libraries, which may yield interesting results", says Leon Marshall, researcher at Naturalis and the Université Libre de Bruxelles.

Disturbing
temperature rise

Calculations showed a temperature rise at the Gavarnie-Gèdre commune in the Pyrenees, at the French-Spanish border. The region appeared to have warmed significantly since the end of the nineteenth century, greater than the global average. “The effects of climate change are more apparent in the mountains. High-altitude areas are therefore important areas for testing the effects of climate change. Temperature increases can occur over relatively short distances in the mountains and this puts pressure on biodiversity”, Marshall explains.

Biodiversity
under pressure

The distribution shift of species to higher elevations causes an increase in species richness at cooler altitudes. More species also means more competition. This pressure could cause species from cooler regions to “fall off the top of the mountain”, when suitable conditions no longer exist. The study did indeed discover an upward shift of the studied plants and bumblebees to higher altitudes, of 229 and 129 meters on average, respectively. It seems that the bumblebees cannot shift at the same speed. "This poses an immediate danger when interdependent species do not simultaneously move upwards", Marshall points out. Some species simply cannot live without each other. Certain plants will miss their pollinators, and insects their food, or both.

Ecoloog Koos Biesmeijer ving en bestudeerde verschillende hommelsoorten in de Franse Pyreneeën.
Ecologist Koos Biesmeijer caught and studied various bumblebees in the French Pyrenees.

 

A delay
in displacement

In general, the studied plants move upwards further compared to the studied bumblebees. This delay can lead to the disruption of mutual interactions, and to certain bumblebees having to adapt or expand their diet. "And since most species are generalists, they seem capable of doing so", Marshall explains. "However, certain species, such as Bombus gerstaeckari, cannot change their diet and are therefore forced to shift with its food source." The specialized pollinator is therefore most at risk, due to its specific feeding habit. “Fortunately, short-term extinction is unlikely. However these species may become restricted to smaller habitats that are under less pressure.”

Grip
on climate change

The results show that it is urgently needed to understand how best to conserve these important, high elevation bumblebee communities. “We plan to repeat similar historical studies with other researchers. We believe that ongoing shifts are occurring, and that these may have been accelerated due to increased human induced pressures. Finding and repeating these historical biodiversity surveys is fundamental to our understanding of the impacts of climate and land use change on species communities. They provide accurate baselines from which we can infer change”, Marshall concludes.

More
information

  • For more information on this subject, please contact Leon Marshall, researcher at Naturalis Biodiversity Center, via leon.marshall@naturalis.nl or +31 0633378879.
  • The first picture was taken by Nicolas Vereecken, Université Libre de Bruxelles.
    The second picture was taken by Koos Biesmeijer, Naturalis Biodiversity Center.
  • The article was published in the scientific journal Proceedings of the Royal Society B. Official title: ‘Bumblebees moving up: shifts in elevation ranges in the Pyrenees over 115 years’. Authors: Leon Marshall, Floor Perdijk, Nicolas Dendoncker, William Kunin, Stuart Roberts and Koos Biesmeijer. Marshall, Perdijk and Biesmeijer are affiliated with Naturalis Biodiversity Center.