Most of Europe's wild bee species have become less widespread over the past century, according to a major scientific study published on October 19, 2026, revealing an extensive decline that can remain hidden behind apparently stable biodiversity figures.
The peer-reviewed study published in Proceedings of the National Academy of Sciences (PNAS) examined more than four million records of wild bees and hoverflies collected across Europe between 1921 and 2020. Researchers found declining geographic occupancy among most bee species with estimable trends and approximately half of the hoverfly species.
Crucially, the findings suggest that counting how many species remain in a region may conceal significant changes in their distribution. Many species can become increasingly restricted even when overall species richness changes relatively little.
What the Century-Long Pollinator Study Found
Led by Carlos MartÃnez-Núñez of the Spanish National Research Council (CSIC), the international research team assembled a dataset covering approximately 88% of Europe's known bee and hoverfly species. The analysis examined species persistence, regional species richness and geographic occupancy over a 100-year period.
The results revealed contrasting patterns between the two pollinator groups. Most wild bee species for which researchers could estimate trends showed declining occupancy, while approximately half of hoverfly species experienced similar decreases. Hoverflies are flies that often resemble bees or wasps and play important roles in pollinating flowering plants.
According to an expert assessment published by Science Media Centre Spain, the average occupancy of European bees declined by approximately 0.4% annually across the study period, equivalent to nearly one-third over a century.
That figure describes an estimated change in geographic occupancy, not a direct count of individual bees lost each year. It also does not mean that all European bee species declined at the same rate.
Hoverflies displayed a more complicated pattern, with substantial differences between species. The proportion showing declines should not be confused with the average change across the entire group.
Why Stable Species Counts Can Hide Biodiversity Loss
One of the study's most important findings concerns the difference between species richness and geographic occupancy.
Species richness measures how many different species are recorded in an area. Occupancy, by contrast, estimates the probability of finding a particular species at a given location.
A region could therefore maintain a similar number of species while individual species disappear from places where they were previously recorded. More adaptable species may expand into areas where environmentally sensitive species have declined.
This process can alter the composition of pollinator communities without producing an equally dramatic change in the total number of species present.
That distinction matters because different pollinators do not necessarily perform identical ecological functions. Some species specialize in particular flowers or environmental conditions, meaning their decline may affect plant reproduction in ways that overall biodiversity counts fail to reveal.
Nevertheless, the study did not directly measure a continent-wide decline in pollination services. Changes in ecosystem functioning remain an important potential consequence rather than a quantified outcome established by these records.
Why Europe's Pollinator Trends Differ by Region
The decline was not geographically uniform. Researchers identified persistent reductions in species richness in Europe's Atlantic and Continental biogeographic regions, while other areas showed mixed or more favorable patterns.
In the Alpine region, bee species richness showed recent increases, contrasting with the broader pattern of declining occupancy found across much of Europe.
These differences may partly reflect changing environmental conditions. Some species adapted to warmer temperatures appear to be expanding, while cold-adapted bees, including certain bumblebees, may face greater pressure.
Scientific commentary accompanying the publication noted that the Alpine findings are consistent with some species expanding into higher elevations as temperatures rise. However, this does not establish that climate change is beneficial for Alpine biodiversity overall.
Regional averages also conceal local differences. Individual habitats and species can experience substantial declines even where broader regional indicators remain relatively stable.
What the Evidence Can—and Cannot—Tell Us
The study's unusually extensive dataset provides valuable evidence of long-term changes in European pollinator distributions. However, historical occurrence records have limitations that require careful interpretation.
The researchers used statistical occupancy models to account partly for differences in recording effort over time. These methods help identify distributional trends, but the underlying observations were not collected through one consistent monitoring program spanning the entire century.
Historical sampling was especially uneven. Northwestern Europe has generally been studied more intensively than southern and eastern regions, while records from the earlier decades are comparatively sparse.
As a result, researchers could estimate occupancy trends for only around 40% of the species included in the broader dataset, according to the expert assessment published by Science Media Centre Spain. These species tend to be more commonly recorded, limiting how confidently the findings can describe rarer pollinators.
The distinction between decline and extinction is equally important. Approximately 91% of the species documented across the historical records were also recorded during 2001–2020.
The absence of recent records for the remaining species does not prove they have disappeared from Europe. Researchers cautioned against interpreting the findings as evidence of widespread continental extinctions.
Habitat loss, agricultural intensification, pesticide exposure and climate change are recognized pressures on pollinators. However, this particular analysis does not establish the precise causal contribution of each pressure to every observed species decline.
What the Findings Mean for Pollinator Conservation
Wild pollinators contribute to the reproduction of flowering plants and support agricultural production, including many fruit and vegetable crops. Their ecological importance extends well beyond managed honeybees, which cannot automatically replace the diverse functions performed by wild species.
The new findings reinforce concerns documented in separate conservation assessments. In October 2025, the International Union for Conservation of Nature reported that approximately 10% of assessed European wild bee species were threatened with extinction.
That extinction-risk assessment measures something different from the new study's historical occupancy trends. A species can become less widespread without immediately qualifying as threatened, while a species already facing extinction risk may require especially urgent protection.
Conservation priorities include protecting and restoring flower-rich habitats, maintaining diverse agricultural landscapes, reducing harmful pressures from intensive land management and improving long-term monitoring.
More systematic surveys would also help scientists distinguish genuine ecological changes from gaps in historical recording, particularly in poorly sampled regions and among uncommon species.
The research arrives as governments gather in Yerevan, Armenia, for the COP17 United Nations biodiversity summit. As The Guardian reported, the findings add urgency to discussions about protecting biodiversity and tracking progress toward international conservation commitments.
Importantly, the evidence does not suggest that Europe's wild pollinators have already experienced widespread species extinction. Most historically recorded species still have modern records, leaving opportunities to protect populations and restore habitats.
The central warning is more subtle: pollinator communities can undergo substantial ecological change long before their overall species counts reveal the full extent of the decline.
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