About 90% of the world’s flowering plants depend upon animal pollination for reproduction. Furthermore, many food chains are based on these plants. Specifically, the pollination of crops in cold and temperate regions of the northern hemisphere is especially important thanks to the bumblebee genus (Bombus), which belongs to the Hymenoptera family.
However, a study published in Nature ensures that high temperatures and the increase in extreme weather events threaten their pollination work. These factors, since they can reduce their fertility and even alter their cognitive abilities, particularly affect these insects.
Address known causes to prevent decline
The authors of this research state that preventing their decline, whether of arctic, alpine bumblebees or other origins, requires directly addressing the known causes of their disappearance.
Guillaume Ghisbain, co-lead author and researcher at the Free University of Brussels and the University of Mons, told SINC that the degradation of their natural habitats is one of the multiple causes, which is due to urbanization, the transformation of the landscape for intensive agriculture, and soil contamination. He also stated that climate change and its various facets, such as heat waves, droughts, and other extreme climate phenomena, along with the extensive use of herbicides, fungicides, and insecticides, are affecting them.
This genus of hymenoptera is especially important for the pollination of crops in cold and temperate regions of the northern hemisphere.
Therefore, he adds, “Developing a comprehensive and large-scale understanding of their decline is essential to hope for halting the decline of their populations.”
Ghisbain’s team quantified the past, present and future habitats in Europe for these bumblebees. To do this, it collected observational data from 1901 to 1970, from 2000 to 2014 and projections until 2080.
The suggestion is that at least 90% of its territory will be lost in the same period. In Europe, the suggestion is that the range of around 38% to 76% of European bumblebee species, currently considered non-threatened, will shrink by at least 30% from 2061 to 2080. Species from arctic and alpine environments may be on the brink of extinction in Europe.
Scandinavia, a possible escape
In this scenario, experts consider that displaced species could potentially seek refuge in Denmark, Norway and Sweden.
The researcher said, “Bumblebees are organisms typically adapted to temperate or cold climates.” Their evolutionary history goes back tens of millions of years, emerging during a period of significant cooling in the northern hemisphere. Even now, these creatures primarily inhabit regions with colder climates.
“He adds that the models they have developed indicate that many species could remain suitable for the ecological conditions of certain areas of Scandinavia – a region of Europe that is climatically and ecologically particularly favorable for bumblebees – in the future.”
However, the authors also highlight a drawback to this option: ensuring that it excludes factors not considered in their models, such as heat waves, droughts, extensive pesticide use, among others, will be crucial for this region to effectively sustain a diverse bumblebee community in the future.
Another important risk is that if many species converge in the same area, they could geographically concentrate their parasites, which could affect their communities. Finally, there are no guarantees that bumblebees will be able to migrate to this region from lower latitudes.
It is urgent to protect their natural habitats
All the efforts that society makes to reduce our climate footprint will benefit the survival of these populations in the medium and long term for researchers. Furthermore, ensuring that their current habitats do not continue to undergo landscape transformation is essential.
Ghisbain emphasizes that preserving and restoring the ecosystems in which these bumblebees reside and, more importantly, promoting connectivity between these habitats is crucial so that they have enough space to establish large populations that can communicate with each other.
Researchers state that limiting the increase in global temperature requires reducing greenhouse gas emissions, especially carbon dioxide, methane, and nitrous oxide. This is among the measures that must be taken because the causes of the decline are “multifactorial.”
The issue is that only a few insect species pollinate certain flowering plants. Conversely, public awareness and consumption habits should focus on buying food produced using environmentally friendly methods that benefit both ecosystems and humans.
Impact on agricultural production
The agricultural sector will be most affected by the decline in activity, with obvious consequences for human nutrition and the economy. “The scientist emphasizes that a few insect species in natural ecosystems pollinate certain flowering plants, and if these insects vanish, it could lead to a significant decline in the wild plants themselves.”
This prediction also impacts herbivores and, subsequently, the carnivores that consume them. In short, if pollinators decline, there will be cascading consequences.
In a time when agriculture dedicates a substantial portion of land, we must reassess global land use policies. This reassessment should prioritize conserving pollinator diversity at the same level as preserving other resources. The expert proposes that governments should promote policies strengthening pesticide regulations to address landscape pollution.
Bumblebees vs. domesticated bees
This study doesn’t easily apply to honey bees because they differ significantly from bumblebees in both ecology and physiology. Ghisbain explains, “For instance, bumblebees tend to exhibit more specialized foraging habits than honey bees; they rely on specific plants to sustain their communities.”
Plants within the Fabaceae family, for example, play a crucial role for many bumblebee species, and the absence of these plants results in the decline or disappearance of certain species.
In contrast, honey bees possess a more versatile diet, allowing them to gather pollen and nectar from a wider variety of floral species. Moreover, humans control their reproduction. Ghisbain points out, “This capability enables us to relocate a hive containing thousands of individuals to a specific location, a practice that the majority of bee species cannot achieve.”
Nevertheless, a shared factor between honey bees and bumblebees is that a high-quality natural environment, rich in various wildflower species, with minimal or no pesticide use and limited urban development, greatly benefits their population health.
Similarly, both domestic and bumblebees are impacted when droughts or heat waves lead to mass die-offs of the flowering plants they rely on for resources. The scientist emphasizes, “Thus, caring for the climate and ecosystems will have highly positive effects for both wild and domesticated bees.”
Particular case of the Iberian Peninsula
On a European scale, there are over 2,100 species of wild bees, which are not domesticated like the honey bee (Apis mellifera). Spain, similarly, ranks as the second country in Europe with the highest diversity of wild bee species, trailing only behind Greece.
“Every year, Spain unveils new bee species previously unknown to science, solidifying its status as a biodiversity treasure. However, bumblebees exhibit limited diversity in most of the Peninsula, largely due to the hot and arid climates in many regions,” Ghisbain explains.
To encounter thriving bee communities in Spain, one must venture to the Cantabrian mountain range and the Pyrenees. Nevertheless, a few bumblebee species are already witnessing declines in these regions. The expert concludes, “Preserving these havens of diversity by mitigating anthropogenic stress factors is absolutely essential.”
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