Changing odour landscapes: the effect of anthropogenic volatile pollutants on plant–pollinator olfactory communication

Olfactory signals, often in synergy with visual signals, mediate the interactions between plants and animals. However, urbanization and agricultural practices are both sources of volatile organic compounds (VOCs) and reactive oxygen species (ROS) that have the potential to interfere with plant–animal communication and to disrupt mutualistic interactions. In this review, we explore how anthropogenic airborne pollutants may disrupt chemical information transfer between flowering plants and flower visitors. The emission of anthropogenic volatile pollutants (AVPs) including VOCs and formation of ROS, for example from traffic or industries, and non-natural biogenic VOCs, for example from introduced crops, may have a number of effects: (i) changes in plant signalling as a consequence of plants experiencing physiological stress; (ii) chemical interference (chemical degradation/transformation of infochemicals); (iii) increased levels of background noise impeding signal detection; and (iv) changes in pollinator signal perception and behaviour. All of the above in turn could have consequences for the biological fitness of plants and animals that rely on olfactory information as pivotal functional signals. The study of anthropogenic airborne pollutants and their effects on plant signalling is just emerging and the impacts of this aspect of anthropogenic emissions are barely understood. Volatiles emitted from anthropogenically changed landscapes could, however, have far-reaching consequences for ecosystem functioning in adjacent natural zones, particularly in fragmented landscapes. In response to the wide gap in our knowledge on the mechanisms that govern interference of anthropogenic VOCs with olfactory information, future research directions are proposed with the aim to inspire research to help elucidate the risks of anthropogenic VOCs for plant–pollinator communities and improve risk assessment strategies. A lay summary is available for this article.