Plight of the Bumblebees: How Traffic Noise Disrupts Bumblebee-Mediated Tomato Pollination
Featured Image Caption: A bumblebee covered in pollen sits on a blooming flower. Image Source: Judy Gallagher via Flickr, CC-BY-2.0.
Source Article: Varga-Szilay Z, Szövényi G, Pozsgai G. 2025. Anthropogenic noise can decrease tomato reproductive success by hindering bumblebee-mediated pollination. Basic and Applied Ecology. 87:11–19. doi: 10.1016/j.baae.2025.05.008
Supplementary Sources:
- Pyko A. et al. 2023. Long-term exposure to transportation noise and ischemic heart disease: A pooled analysis of nine Scandinavian cohorts. Environ Health Perspect. 131(1): 17003. doi:10.1289/EHP10745.
- Clark C. et al. 2017. Association of long-term exposure to transportation noise and traffic-related air pollution with the incidence of diabetes: A prospective cohort study. Environ Health Perspect. 125(8): 087025. doi:10.1289/EHP1279.
- Cocenas-Silva R., Droit-Volet S., & Gherardi-Donato E. C. S. 2019. Chronic stress impairs temporal memory. Timing Time Percept. 7(2): 108–130. doi:10.1163/22134468-20191138
(W)Ringing (Y)Ears: Chronic Noise Exposure Harms Human Health
People are noisy! Whether it be the screeching of brakes on a city bus, the wailing sirens of a passing firetruck, or the regular din of rush-hour traffic, humans have created an outdoor environment that is overwhelmingly packed with constant noise.
Although we may be able to tune it out, our bodies have not adapted to life in an urban soundscape. Health issues such as heart disease1, diabetes2, and memory impairments3, among other unwanted complications, all may be associated with life in the big, clamorous city.
But how does all this racket affect the organisms that live alongside us?
Bumble, Bumble, Toil and Trouble: Human-Based Noise May Disrupt Bumblebee Pollination
Studies have shown that some animals, such as birds and marine mammals, can experience increased levels of stress and impaired communication because of anthropogenic (human-based) noise pollution. However, little is known about how this new noisy world affects bumblebees. Do they avoid areas with more noise, or are they able to cope with the commotion?
As pollinators, bumblebees (Bombus sp.) are key to the continued success of wild-grown plants and farm-grown crops. In fact, bumblebees have been sold commercially to farms since the 1980s, leading to increased overall yield of fruits, as well as improvements in the weight, size, and taste of produce. Therefore, if noise pollution negatively affects the pollination behavior of bumblebees, agriculture may begin to suffer as the human population continues to grow.
Make Some Noise! Exposing Bees and Tomato Plants to Different Decibel Levels
In response to this mounting concern, researchers at Eötvös Loránd University and the University of the Azores decided to investigate how well buff-tailed bumblebees (Bombus terrestris) could pollinate tomatoes under different levels of simulated anthropogenic noise.
To do so, they began by planting and growing tomato crops in a controlled greenhouse environment. Once the plants were ready for pollination, they were separated into three treatment groups, which determined the level of noise exposure as well as whether the bumblebees would have access to the plant’s flowers.
One group of tomato plants (referred to as “DN-open”) had a mini Bluetooth speaker placed within 10 cm of select flowers. The speaker played traffic noise between 60 dB and 90 dB while the bees were interacting with the plants, which is a level of intensity comparable to the actual volume of traffic noise. The plants were left physically unobstructed, allowing bumblebees to pollinate the crops at will.
A second treatment group (referred to as “NN-open”) had a fake paper speaker placed beside each tomato flower and were left unobstructed, creating a consistent physical environment between this treatment and the previous one. However, these crops were not exposed to any traffic noise.
A final treatment group (referred to as “NN-bagged”) had neither a real nor fake speaker placed next to the flowers. Instead, a mesh bag was placed over top of the whole plant, preventing the bumblebees from pollinating the plants. This meant that self-fertilization was the only fertilization process taking place for these crops.
Once the experiment was set up, bumblebees were allowed to interact with the plants for three hours. After this period, all the plants were bagged to prevent any further pollination.
Tomat-Oh No! Noisy Environments Reduce Bumblebee Pollination
Three key measures were used to determine pollination success between the treatments: bumblebee bite marks on the flowers, market value of the resulting tomatoes (as determined by local farmers), and the number of seeds per tomato.
The researchers hypothesized that these three metrics would all be lower in the “DN-open” condition (the “noisy” condition) compared with the “NN-open” condition (the “non-noisy” condition), since traffic sounds should deter pollination behavior. Essentially, flowers with more bite marks, better-quality tomatoes, and higher seed counts would have been pollinated more frequently.
So, were their predictions correct? Kind of.
There was no difference in the number of bite marks on the flowers between the “DN-open” and “NN-open” groups. Additionally, tomatoes from all three treatment groups were of similar quality in terms of size and color, so traffic noise did not lead to lower market value for these fruits. At first glance, these results suggest that the bumblebees were unbothered by all the racket.
However, one key finding suggests that noise truly does decrease pollination activity: “DN-open” tomatoes had significantly fewer seeds than “NN-open” tomatoes. Since seed count has historically been used as a reliable measure of pollination and is extremely sensitive to small changes in pollination activity, this metric was seen as the gold standard for evaluating bumblebee activity. The other measures, although important, were less reliable and somewhat subjective.
The number of seeds per tomato is an excellent indicator of pollination success. Image Source: Varga-Szilay Z, Szövényi G, Pozsgai G. 2025. Anthropogenic noise can decrease tomato reproductive success by hindering bumblebee-mediated pollination. Basic and Applied Ecology. 87:11–19. doi: 10.1016/j.baae.2025.05.008.
Planting the Seed: Where Do We Go from Here?
Based on these results, this study concluded that noisier environments do negatively affect bee-mediated pollination of tomato plants. However, there is still a long way to go to fully understand how closely noise pollution and pollination success are intertwined. For example, does the noise just affect the bees, or could it impact the plants themselves? Are these results consistent across plant species, or are they limited to tomatoes?
With urban infrastructure gradually encroaching on farmland, it’s important to work towards answering these questions, as well as the many others that will undoubtedly help improve modern agriculture. Unfortunately, it isn’t possible to just give bees little earplugs and call it a day (partially because they have no ears!). Despite this, with continued research and collaboration with farmers, agricultural practices will surely shift and grow to succeed in the hustle and bustle that the future will bring.
Reviewed by: Cassie Welander
