A Century of Records Shows Most of Europe's Wild Bees Losing Ground

Over the past hundred years, the typical wild bee species in Europe has become about a third less widespread. That is the central finding of a new study published this week in the Proceedings of the National Academy of Sciences, built on more than four million records of bees and hoverflies collected across the continent between 1921 and 2020.

The study, led by researchers at Spain's Doñana Biological Station, paints a picture that is worrying but not hopeless: most bee species are losing ground, yet the great majority are still found somewhere on the continent. For Silicon Valley, it is also a story about data, because the result depends on stitching a century of scattered observations into one consistent picture.

What a Century of Records Shows

The team, headed by ecologist Carlos Martínez-Núñez of the Doñana Biological Station, part of Spain's national research council CSIC, worked through records for about 88% of the roughly 3,051 bee and hoverfly species known in Europe. After honeybees, these two groups are among the continent's most important pollinators.

Most wild bee species shrank in range over the century. Averaged across Europe, the typical bee species lost about 0.4% of its range each year, which adds up to nearly a third over a hundred years. About half of hoverfly species declined too, although hoverflies as a group expanded their range in earlier decades.

The losses were not spread evenly. Species richness fell steadily in the Atlantic and Continental regions, which take in Britain, France and much of Central Europe, and bees vanished from more areas in the north and south of the continent, with declines speeding up in recent decades.

In practice, a smaller range means a species turns up in fewer places than it once did. A bee that was common across an entire country a century ago may now hang on only in scattered pockets, leaving local wildflowers and crops with fewer visitors even if the species is not officially endangered.

Winners, Losers and the Alps

The Alps were the exception. There, bee species richness actually rose in recent decades, and some warm-adapted pollinators appear to be moving into new territory, perhaps by heading up mountain slopes as temperatures climb. Bees suited to the cold, in contrast, tended to fare worse than those that prefer warmer conditions.

Still, Europe has not lost most of its pollinators outright. Of the species recorded over the past century, close to nine in ten bees and hoverflies were still being found in the last two decades. As the authors put it, "Species richness alone provides an incomplete picture of biodiversity change." A species can survive on the continent while vanishing from much of the landscape where it once lived.

Why Wild Bees and Hoverflies Matter

Honeybees get most of the attention, but wild bees and hoverflies do a large share of the pollination that keeps ecosystems and farms going. About 90% of flowering plants and more than three-quarters of the world's major food crops depend at least in part on animal pollinators.

Researchers point to a familiar set of pressures behind the declines: lost and fragmented habitat, intensive agriculture, pesticides and other pollutants, and rising temperatures. Because these pressures overlap, it is hard to single out one cause, but the pattern of cold-adapted species losing ground fits a warming climate.

Hoverflies deserve more credit than they get. Often mistaken for small bees or wasps because of their striped bodies, they visit a wide range of flowers as adults, and the larvae of many species eat aphids, which makes them a natural form of pest control on farms and in gardens. Losing them can hurt crops twice over.

How Scientists Read Four Million Records

The records behind the study come from many sources over many decades: museum collections, field surveys and observations by amateur naturalists. That kind of data is messy. Some regions and periods were studied far more closely than others, so a simple count would confuse changes in survey effort with changes in bees. The team used statistical occupancy models and sensitivity checks to correct for those biases.

Independent experts were impressed. "This is a very high-quality piece of work, based on a very solid database," said Ainhoa Magrach, a research fellow at the Basque Centre for Climate Change, in comments published by Spain's Science Media Centre. Concepción Ornosa, a retired biodiversity researcher at the Complutense University of Madrid, agreed that "the conclusions are supported by sound data." Magrach also pointed to limits: trends could be estimated for only about 40% of species, mostly common ones, and northwestern Europe is far better sampled than the south and east.

What It Means for California

Europe is not California, but the lessons travel. California's farm economy, from Central Valley almonds to orchards and berry fields, leans heavily on pollinators, and growers already rent huge numbers of managed honeybee hives every spring. Wild bees provide a backup that grows more valuable as managed colonies face their own losses.

The study also shows the value of long-term, public biodiversity data, an area where the Bay Area has deep roots. iNaturalist, the citizen science platform that lets anyone log a photo of a plant or insect, began as a UC Berkeley student project, and records like these increasingly feed scientific studies of how species are shifting.

Policy is already catching up in Europe. The European Union's Nature Restoration Law, adopted in 2024, commits member states to reversing the decline of pollinator populations by 2030. Studies like this one give regulators the long baseline they need to tell whether that goal is being met, and the same is true for any state or federal program that tries to protect pollinators in the United States.

Can Technology Help Pollinators Recover?

The prospects are real. Better data means better targeting: if scientists know which species are declining and where, conservation money can go to the habitats and regions that need it most. Image recognition apps, automated insect cameras and acoustic sensors could fill gaps in poorly sampled regions, and machine learning can sort millions of observations faster than any team of specialists. "This means there is still scope to reverse the trend if action is taken in time," Magrach said, pointing to the fact that most species are still present.

There are concerns as well. Technology cannot replace the habitat pollinators need, and automated identification still struggles to tell many bee species apart without an expert and a microscope. Data from apps tends to cluster where people live and travel, which can repeat the same geographic biases the study had to correct for. And some proposed fixes, such as robotic pollinators, treat the symptom rather than the cause.

There is a policy debate, too. Farm groups and environmental organizations often disagree over how fast to restrict pesticides and how much land to set aside for wild habitat, and the costs fall unevenly on farmers. Some ecologists argue that a slow, steady decline like this one is easier to ignore than a dramatic collapse, which makes political action harder to win.

The signals to watch are specific. Will Europe's restoration and pollinator policies produce measurable gains in the regions with the steepest losses? Will monitoring expand in southern and eastern Europe, where data is thinnest? Can automated tools reliably identify wild bees at scale? And will similar long-term studies in North America show the same pattern?

Listening to Nature With Technology

At Sparknify we follow how Silicon Valley tools are changing the way we understand the natural world. We recently looked at one example in This San Francisco Startup Says Plants Have Been Talking All Along, where sensors and AI are used to read signals from plants. The pollinator study shows the other half of that story: before technology can help nature, someone has to collect, clean and make sense of the data.

A century of careful records has shown where Europe's wild bees are disappearing; the next century of data may decide whether they come back.

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