Plastic pollution harms bees, review finds

Plastic from films, fertilizers, water, and the air ends up on farmland

Microplastic particles are between one micrometre and five millimetres in size; still smaller particles are referred to as nanoplastics. Whereas the harmful effects of NMP in water and for individual species are well documented, there have as yet been no systematic reviews on how the particles affect agricultural ecosystems. To fill this gap, the authors of the review summarized 21 already published individual studies for the first time. They were interested particularly in the question of how pollinator insects and other beneficial insects come into contact with NMP and what consequences the ingestion of the particles has for them, as well as for the ecosystems that are dependent on them and for agricultural production.

In this way, the researchers first succeeded in identifying different sources from which NMP end up on agricultural land, including plastic films, fertilizers, polluted water, and atmospheric depositions. The plastic particles accumulate in the soil, and pollinators and beneficial insects that are important for pest control ingest them from the air and food or use them to build nests.

Damage to bees could lead to a decline in agricultural production

The authors of the study establish that the bees' ingestion of NMP leads, for example, to damage to their digestive system, to a weakening of their immune system, and to changes in their behaviour. This makes the bees more susceptible to diseases, possibly causing them to pollinate plants less effectively. 'We find microplastic in the gut of bees and see how wild bees use plastic to build nests. We therefore urgently need to investigate what interaction this has with other stressors, such as climate change, for the bees and their pollination services', says Prof. Dr. Alexandra-Maria Klein, co-author of the study and professor for nature conservation and landscape ecology at the University of Freiburg. A decline in pollination services has a negative effect on crop yield. Thus, plastic pollution could further aggravate existing uncertainties in the global food supply, the researchers warn.

Interactions with other environmental stressors exacerbate the problem

In addition, NMP also exacerbate the threats posed by other environmental stressors, such as pesticides, chemical pollution, fungi, and pathogens. For example, some areas become 'hotspots', where plastic particles interact with harmful viruses. As a result of such interactions, NMP could have serious effects on pollinators and thus on the stability of the food system.

However, the researchers also emphasize the limitations of their review. For example, only little data is available on important pollinators and beneficial insects like bumblebees and ladybirds. In addition, the current data doesnot allow for a differentiated account of the effects of different sizes and amounts of NMP. Researchers urgently need to conduct further studies to better understand the growing problem of plastic pollution and find solutions to it. 'It is already clear today, however, that there is a pressing need for political control of plastic pollution', says Klein.

The study included researchers from Westlake University (Hangzhou, China), Zhejiang University, (Hangzhou, China), Fudan University (Shanghai, China), and the Universities of Freiburg and Tübingen.