Anthropogenic noise can decrease tomato reproductive success by hindering bumblebee-mediated pollination

Anthropogenic noise is a little-studied type of pollution that negatively affects the physiology, nervous function and development of insects. Thereby, it has the potential to disrupt even key ecological services such as pollination. Here, we investigate the effects of anthropogenic noise on the pollination success of tomatoes pollinated by Bombus terrestris, under controlled conditions. We hypothesised that bumblebees avoid flowers exposed to noise more than flowers in non-noisy environments, leading to less efficient pollination and lower fruit quality. Three treatments were applied to randomly chosen plants and flowers in polytunnels in Hungary: noisy (with played traffic noise and allowing bumblebees to access the flowers); and two non-noisy, one allowing bumblebees and one excluding them. The flowers were bagged with nets before anthesis to prevent bumblebee visits, opened/unbagged exclusively during treatment, and re-bagged for three more days post-treatment. We recorded the market value of the fruits and the number of seeds they produced. We found no significant differences in the market value of fruits among treatments, but the number of seeds was significantly lower in the noisy treatment, suggesting that anthropogenic noise has substantial effects on bumblebee-mediated pollination. Although these effects may be mitigated by habituation, loud external noise of various machines (e.g. irrigation systems) within polytunnels is still likely to contribute to the everyday noise exposure of bumblebees and could thus potentially lead to hidden economic losses in production. Therefore, further research is needed to understand the behavioural effects of both direct and indirect noise pollution on bumblebees.