Old Honey Samples Reveal Changes In Bee Interactions Over Decades

Researchers show how 50-year-old honey may illuminate shifts in pollination and microbial exposure.

Honey, often viewed simply as a sweet treat, is now being recognized for its potential to provide deep insights about environmental changes over decades. Researchers from Ume University have found ways to extract and analyze DNA from honey produced as long ago as 50 years, allowing them to reconstruct the interactions between honey bees, the plants they visited, and the microorganisms present, thereby filling important gaps in our ecological history.

Published on March 14, 2025, the study investigates the historical baseline of these interactions, which have become increasingly difficult to assess against the backdrop of climate change and land-use alterations. Traditionally, knowledge about what plants honey bees have pollinated or what microbes they may have interacted with has been largely anecdotal or based on current patterns rather than historical data.

This research analyzed four honey samples collected from South Finland between 1967 and 1972 and compared them to eight new samples gathered from the same region in 2019. By utilizing DNA metabarcoding—an advanced technique for analyzing DNA from complex samples—the team successfully identified and quantified the plant, bacterial, and fungal DNA present in these honey samples.

Interestingly, the study revealed substantial differences between the ancient and modern samples. The researchers found 62 plant ZOTUs (Operational Taxonomic Units) representing 20 genera and 19 families from the old samples, whereas the new honey contained 159 plant ZOTUs, indicating more varied foraging behavior of modern honey bees. The older honey samples had approximately 10,336 sequences for plants, compared to the newer samples, which averaged 12,746 sequences. These findings suggest significant shifts in the types of plants visited by honey bees, perhaps due to environmental changes or shifts in agricultural practices.

For bacteria, the analysis showed 249 ZOTUs, 46 genera, and 36 families present in older honey samples, compared to just 122 bacterial ZOTUs found in newer samples. Notably, the new honey had high levels of the genus Apilactobacillus, which was absent from the old samples, highlighting how modern honey bee interactions have evolved alongside changes in the agricultural environment.

Fungal DNA findings were similar; the older samples identified 44 ZOTUs, six genera, and seven families, whereas new samples revealed 101 ZOTUs, indicating changes or losses of microbial diversity and populations over the decades. The significant variations observed raise questions about the ecological impacts on honey bee populations and their surrounding environments, prompting the need for more extensive biogeographical studies.

The researchers noted the importance of preserving old honey samples, even those stored under varying temperature conditions for decades. The findings indicate the potential for using honey as historical records—similar to the research conducted on ancient sediments or teeth—to provide insights about ecological interactions over extended time periods.

Dr. Anna R. Cirtwill, lead author of the study, explained, "This research offers us invaluable insight. Honey's role as more than just food can redefine its place within ecological studies, allowing us to peer back through layers of time at the interconnections between bees, plants, and microbes. It is both exciting and sobering to think about how our ecosystems have changed and continue to change."

The historical baselines garnered from these ancient honey samples can significantly inform conservation strategies and agricultural practices today. By identifying which plants supported honey bee populations historically, ecologists can derive recommendations for current environmental management strategies aimed at preserving biodiversity and ensuring the sustainability of pollinator species.

Overall, the study broadens the scope of ecological research, proposing honey as not only nourishment but also as a time capsule of ecological interactions. It highlights the need for continued investigation of historical biological data and its relevance to contemporary ecological challenges.

With global declines of pollinator populations, the urgency to understand and mitigate these trends becomes clearer. The study not only marks the potential for honey to serve as historical evidence but also opens the door for future inquiries aimed at preserving the delicate balance within ecosystems.