Scientists Investigating Parisian Beehives Found A Deadly Remnant Of Notre-Dame’s Fire Hidden Inside

On an urban rooftop above the River Seine in France’s capital, beekeepers carefully remove a sheet of honeycomb from a teeming hive. Iconic structures punctuate the sprawling Paris skyline: the Eiffel Tower, the Arc de Triomphe, the charred shell of Notre Dame cathedral. The beekeepers locate a wax-sealed cell and extract a sample of honey. And when scientists analyze its contents back at the lab, they uncover a dark and disturbing secret…

Constructed over several generations between 1163 and 1345, Notre Dame Cathedral has witnessed 850 years of French history. Perched on a riverine island in the medieval heart of Paris, it is a singular gothic masterpiece with fearsome gargoyles and soaring vaults – a symbol of France itself. But in April 2019 disaster struck: a fire broke out in its attic, probably sparked by an electrical short-circuit.

The flames quickly spread, and soon a monstrous blaze had engulfed the landmark. Firefighters battled the inferno for hours. Its distinctive rooftop, which was known as “The Forest” on account of its ancient wooden rafters, was lost forever. Its distinctive spire, known as “The Arrow”, tumbled too. But the main structure held. And eventually the fire was extinguished.

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As the cathedral smoldered in the aftermath, the fate of three beehives on the sacristy roof was uncertain. Installed in 2013 as part of a biodiversity drive, the hives had been home to some 180,000 honeybees. Their yard had not collapsed, but the blaze had reached blistering temperatures of roughly 1,470°F. Could any living thing survive such heat?

Meanwhile, researchers soon discovered that the hives on the sacristy roof were not the only ones at risk. Indeed, the impacts of the blaze extended far beyond the vicinity of the cathedral. Scores of hives and hundreds of thousands of bees right across the city had been touched by the disaster. The proof was in their honey.

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Of course, the impact had been exacerbated by the booming urban beekeeping scene. According to one estimate, the number of hives in the city may have more than trebled over the last decade, from 300 to more than 1,000. Scores of Parisian businesses and public landmarks now have working hives on their roofs, including the Grand Palais, the Opera Garnier and, of course, Notre Dame Cathedral.

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As such, delicious local honey can be found in the prestigious La Grande Épicerie de Paris food hall alongside other gastronomic delights. In fact, Parisian honey is now considered the finest in France. Where a pound of rural French honey tends to sell for around $12 to $23, the same quantity of Parisian honey can fetch $65.

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Naturally, discerning French chefs such as Michelin-starred Jérôme Banctel, along with Thierry Marx and Guy Savoy use Parisian honey in their recipes too, as beekeeper Audric de Campeau explained to the offbeat travel website Atlas Obscura in 2018. He said, “The honey is really delicious, it’s not a marketing thing… [it’s] a real prestigious recognition of our work.”

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That said, French fascination with bees is hardly a new phenomenon. Napoleon identified so much with the buzzing creatures that he used them as a personal and imperial logo. Likewise, bees have been adopted as icons by several prestigious institutions, including the Louvre art museum and the Guerlain perfume house. Hard-working and harmonious, bees are potent symbols of craft, community, diligence and industry.

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The bees on the roof of Notre Dame were in fact a type of European honeybee known as the Brother Adam Buckfast. Brother Adam was a Benedictine monk of German origin who arrived at Buckfast Abbey in the United Kingdom in 1910. By 1919 he was managing the monastery bee yard; in the 1920s he crossbred Italian and English bees to produce his own variety.

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Buckfast bees are highly productive. Their colonies can grow large and fast, particularly in the spring. They tolerate cold, damp weather, fare well in temperate climates, and tend to conserve their honey stocks in the winter. The insects have a generally mild temperament, rarely swarm and are considered an ideal variety for more inexperienced or casual beekeepers.

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Urban bees, such as those on Notre Dame cathedral, also tend to produce more honey than those in the countryside. Paris may be heavily concreted, but it also has plentiful green spaces. Window boxes, gardens, terraces and parks provide a wide variety of floral resources for the bees to forage. Importantly, those resources tend to be uncontaminated by pesticides.

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In 2018 while speaking to the travel website Culture Trip, the owner of the Opera beehives Jean Paucton suggested that bee mortality was a significant issue in rural France. He said, “Urban beekeeping is the future of apiculture. Most of the beekeepers have taken their hives back to the city because they realised bees were dying 30 percent more in the countryside.”

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The hives on Notre Dame cathedral were managed by a company called Beeopic. Headed by Nicolas Géant, the organization installs and maintains hives at the request of private companies and individuals. Presently, it manages a total of some 350 hives across the city. It has a strong social and environmental ethos, too, having donated hives to a children’s hospital and a prison.

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Speaking to the current affairs website NBC News in 2019, Géant explained that he had always dreamed of having a bee yard on Notre Dame – a building he described as “the most beautiful church in the world.” He said, “There is a historic relationship between the bees and the church. For a long time they used the wax from the bees to make the candles.”

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After the cathedral burned down, Géant waited anxiously for any news about his bees. And there was a sliver of hope. An aerial survey appeared to indicate that the hives were unscathed. He told NBC News, “If you look at the photos from the sky, you see that everything is burnt, there are holes in the roof, but you can still see the three beehives.” He added, “The policemen and firemen won’t let me go up there.”

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Then, a few days later, Beeopic shared a photo of a Notre Dame gargoyle on Instagram. Somewhat miraculously, a cluster of honeybees appeared to be crawling on its neck. The caption read, “Our bees from the Cathedral Notre-Dame de Paris are still alive!! Confirmation from site officials!! ❤🐝❤” Because the hives had been situated 100 feet from the main fire, they had escaped a roasting.

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Furthermore, the smoke had probably done little to the bees, except relax them. Bees have no lungs and apiculturists have long used smoke to sedate them. The fumes apparently inhibit the action of pheromones which would otherwise signal danger. They may also act as a biochemical signal, prompting the bees to consume honey and depart the hive.

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Nonetheless, the company could not physically access the hives for some time. Speaking to the British newspaper The Guardian, Beeopic hive manager Sibyle Moulin said staff used drone footage to assess the health and condition of the bees. She said, “We studied their behavior and saw they were carrying balls of pollen on their feet which meant they were building up stocks of protein to feed the young… it meant the queens were fine.”

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Indeed, according to Moulin, the bees “didn’t seem to have been affected at all.” And when she finally did visit the sacristy roof in July 2019 the hives appeared to be in rude health. Moulin harvested some 145 pounds of honey on that visit, but unbeknownst to her – or anyone else – bees across the entire city had been affected by the fire. Their honey was not as sweet as it seemed.

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To make honey, bees extract nectar from flowers and store it in their so-called honey stomach. They then fly back to the hive and regurgitate their harvest into the mouths of other workers. The workers pass the nectar around and chew it for 30 minutes or so, transforming it into honey.

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Because honeybees tend to forage in a relatively limited radius of 1 to 2 miles, their honey is the exclusive product of nearby blooms. As such, the quality of the nectar is influenced by seasonal changes in the local ecosystem. Moreover, when honeybees forage, they inevitably get plastered with pollen, which then ends up in their honey, changing its flavour and texture.

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For example, blueberry flowers can give honey a fruity flavour and a purplish tint. Buckwheat can make honey rich and smoky. And sometimes tree resin can end up in hives, too, adding a hint of pine or nut. So-called “univarietal” honeys are the product of a single type of flower, usually a crop that is deliberately pollinated by carefully placed hives.

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By contrast, Parisian honey has a distinctive cherry candy flavor thanks to the city’s wide range of blooms. In 2018 while speaking to Atlas Obscura, beekeeper Bruno Petit explained that high biodiversity was also linked to high output. He said, “The difference in yield comes mainly from the floral diversity in Paris. Orange trees, jasmine, and other exotic plants can be found on the Paris terraces.”

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Of course, a great deal can be learned about the environment by analysing the chemical composition of pollen and honey. For example, researchers in Mexico analysed the pollen stores of stingless Melipona beecheii bees to gain insights into rainforest ecosystems. Unlike European and Africanized bees, which tend to pollinate scraggly plants on the understory, Melipona bees were found to pollinate large trees.

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Equally, similar kinds of chemical analyses can identify toxins. In July 2019 scientists from Canada’s University of British Columbia collaborated with Beeopic beekeepers to assess the pollution caused by the Notre Dame fire. They took 36 honey samples from Parisian hives and compared them with samples from the previous year and with 2017 samples from the region of Auvergne-Rhône-Alpes.

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Specifically, the scientists analyzed samples from hives situated downwind from the fire. In a 2020 interview with the science news website Science Daily, Kate Smith, a lead author of the study said that the path of the smoke was easy to determine. She explained, “Because of the way the wind was blowing the night the fire burned, the direction that the smoke plume traveled is well-defined.”

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The scientists found that the honey from hives downwind from the fire contained three-and-a-half times more lead than samples from the previous year. Furthermore, the downwind honey contained four-and-a-half times more of the toxic metal than the countryside honey. Indeed, the content of one sample showed levels a staggering nine times higher than normal.

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Lead was frequently used in construction during the Middle Ages. So when Notre Dame cathedral went up in flames, it released hundreds of tonnes of lead oxide aerosols into the atmosphere. Carried by the wind, clouds of toxic dust settled over the city, contaminating schools, parks, day-care centers and playgrounds. And as the bees foraged local blooms, they brought the dust back to their hives, too.

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Speaking to Science Daily, co-author Dominique Weis said that the findings were unsurprising. She said, “We were able to show that honey is a helpful tracer for environmental pollution during an acute pollution event… It is no surprise, since increased amounts of lead in dust or topsoil, both of which were observed… are a strong indicator of increased amounts of lead in honey.”

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Of course, lead poses severe health risks to humans if consumed in high enough quantities. In fact, lead is a somewhat persistent heavy metal that accumulates in bones and tissues, causing a range of long-term symptoms such as tiredness, abdominal pain, memory loss and headaches. Lead poisoning can cause permanent neurological damage and disturbing behavioral changes in young children, too.

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However, the honey sampled by Weis and Smith was nowhere near such toxic levels. In fact, the honey contained around 2.3 nanograms of lead per gram, meaning it was fit for human consumption under European Union law. Lead does bioaccumulate – that is, it accrues in the body with repeated exposure – but one would have to consume an enormous quantity of the honey to experience a toxic effect.

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As Weis explained to Science Daily, the concentrations were practically negligible. She said, “The highest levels of lead that we detected were the equivalent of 80 drops of water in an Olympic-sized swimming pool. So even if the lead is relatively elevated, it’s still very low. It’s actually not higher than what we see in honey from downtown Vancouver.”

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In fact, the Paris study follows on from another study of beehives in metropolitan Vancouver. Using similar methods of chemical detection, Smith and Weis analyzed beehives in six neighborhoods to find trace quantities of heavy metals. However, Paris differs from Vancouver in one important respect: for centuries, lead was used in Parisian construction work.

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Speaking to Science Daily, Weis said, “In a city as young as Vancouver, we are able to trace sources of the metal using distinct isotopic signatures. In Paris, however, the long history of lead use throughout the city made the interpretations more challenging. This provides an important consideration for future lead sourcing studies in very old cities.”

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For while the honey did not pose any significant safety risks, the lead in the local environment was another story. Controversially, the authorities failed to conduct any toxicity tests in the neighborhoods around Notre Dame for an entire month after the blaze. And according to an investigation by The New York Times newspaper, they had received ample and timely warnings about potential contamination from several civil agencies.

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The tests, when finally conducted, showed that at least 18 primary schools, preschools and day-care centers had been contaminated with more lead than regulations allowed. The soil in some public parks was heavily contaminated, too, and scores of streets and plazas contained as much as 60 times the safe level of lead.

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As detailed in confidential documents from the Culture Ministry, the very worst areas were those closest to the cathedral. However, it took the authorities four months to fully decontaminate them. And as of September 2019 they still had not completed toxicity tests of every school in the immediate vicinity, according to The New York Times.

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Furthermore, according to a study by Columbia University, residents living downwind of the fire within 1,100 yards had probably experienced levels of lead exposure higher than officially indicated. Meanwhile, according to the French news site Mediapart, the Regional Health Agency (ARS) and the Regional Prefecture recorded a dozen cases of lead exposure in children as of October 2019. Some 78 others were under medical supervision.

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More positively, Weis and Smith demonstrated the potential for bees to act as pollution sensors. Since many forms of pollution are diffuse and invisible, researchers typically rely on technology to detect it. Speaking to Science Daily, Weis said, “We were able to show that honey is also a helpful tracer for environmental pollution during an acute pollution event like the Notre-Dame fire.”

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In conclusion, the relationship between bees and humans is ancient and complex. Bees provide human communities with honey, royal jelly and wax, from which scores of products are derived, including food, cosmetics and medicine, to name a few. Now, thanks to advances in chemical analysis, bees are serving as scientific research assistants, too.

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