2023-09-13 15:00:00
In this study, the research team (ULB, VUB, UCLouvain, KU Leuven and UMons) demonstrates a decline in bumblebee populations since 1900 across most of Europe. It also estimates that the distribution areas of these species will undergo significant contractions in the decades to come, in all climate change and land use scenarios considered. Concretely, to obtain their results, the team of Belgian researchers applied a machine learning approach. “These are approaches linked to artificial intelligence to try to estimate the probability of the presence of a given living organism given local environmental conditions,” explains bioengineer Simon Dellicour, researcher at the Free University of Brussels and co-author of the study. Ecological adequacy amounts to asking, for a particular locality, whether we have the probability of observing a specific bumblebee species given the environmental conditions measured at that location. By environmental conditions, we mean here climatic variables such as temperature, precipitation or even land use variables.”
Reduction of territory
A notable result? “We quantified that 75% of the bumblebee species that we studied and which were not classified as already threatened would probably see a reduction of at least 30% of the European territory suitable for their presence within around fifty years. years.”
These figures can be applied to Belgium. “Our analyzes confirm that over the past century – therefore the last decades – there has been a reduction in the ecological suitability of the Belgian territory for bumblebee populations,” continues the ULB researcher. We see a shrinking of the distribution areas of these populations across the entire European continent. The second thing is that in the decades to come, we see that the ecological suitability of the territory will continue to decrease on a continental scale.”
But these figures of 30% reduction in territory for 75% of species similar to the rest of Europe lead to “probably more significant consequences in Belgium because there are more bumblebees than in Spain for example”, estimates Denis Michez, conservation biologist, bee specialist (UMons) and co-author of the study. “Bees, and particularly bumblebees, are responsible for the ecosystem service of pollination. In European ecosystems, flowering plants are dominant and are designed to attract pollinators. These flowering plants are the basis of ecosystems and pollinating animals are vectors of their reproduction, by coming to collect pollen and transporting it to another flower. All animals that depend on these plants – including humans for food! – are indirectly dependent on these pollinators. In this context, the importance of bumblebees will depend on where we are in Europe. You should know that bumblebees are somewhat special bees which are rather adapted to a temperate and cold climate. Their importance in relation to pollination will therefore vary depending on the climate. They are excessively important and largely dominant in temperate climates like here in Belgium and in the north of Europe, they are less important in the South: in Spain or in the south of Italy, for example.”
The worst countries in Europe for bumblebee decline
This knowing that “Belgium and the Netherlands are the worst countries in Europe in terms of bumblebee decline: almost half of the bumblebee species in Belgium have either completely disappeared (20%) or are in great danger (another 20 percent). While on the scale of Europe, no species has yet disappeared. The causes ? Belgium is one of the most densely populated countries with very intensive agricultural practices (fields that are cultivated with a lot of pesticides, a lot of fertilizers, etc.).”
Belgium is therefore one of “the most problematic territories” in terms of the decline of bumblebees in future decades. “These are all countries above the Mediterranean area: the whole of Europe except Portugal, Spain, the south of France, Italy, the Balkans and Greece . These are territories which are currently in a temperate distribution, in which we have many species of bumblebees and where these species will disappear (due to global warming among other things, Editor’s note). The big question is: will they be replaced by others from the South. We ignore it.”
The refuge in Scandinavia?
The scenarios explored highlight that parts of Scandinavia could conversely become potential refuges for European bumblebees. However, we cannot predict whether this area will remain free of additional human-caused stressors not taken into account in the study. There is indeed uncertainty in the capacity of these species to successfully colonize and maintain viable populations in these territories.
The results of this research finally highlight “the crucial role of climate change mitigation policies in protecting these pollinators against anthropogenic transformation of the biosphere.” “Habitat degradation and climate change are acting globally as major drivers of wildlife collapse, with growing evidence that this erosion of biodiversity will accelerate in the coming decades,” the researchers conclude. Belgians.
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