The Impact of Environmental Pollution on Dragonflies and Damselflies (Odonata) and the Role of Climate Change as an Interactive Stressor

Globally, 16% of dragonfly and damselfly species (Odonata) are threatened with extinction, primarily due to the loss and degradation of freshwater habitats. These threats are exacerbated by environmental pollution, particularly from pesticides and heavy metals, and are further compounded by climate change. Despite their recognised value as bioindicators of environmental pollution, comprehensive assessments of the impacts of widespread and hazardous pesticides and heavy metals on Odonata remain limited. The available studies often focus narrowly on either dragonflies or damselflies, specific species, particular life stages, or individual contaminants, resulting in fragmented evidence and substantial knowledge gaps. This review synthesises findings from 54 peer-reviewed articles to assess the effects of pesticide and heavy metal pollution on Odonata across their life cycle, while also considering potential synergistic interactions between these pollutants and climate change. Three categories of impact were assessed: (1) community composition and diversity metrics, (2) mortality and sublethal effects, and (3) behavioural endpoints. Across these categories, broad-spectrum neurotoxic insecticides-particularly neonicotinoids (e.g., imidacloprid), phenylpyrazoles (e.g., fipronil), and pyrethroids-emerged as the most harmful pesticide groups. Among heavy metals, copper was consistently identified as the most toxic. Evidence for synergistic interactions between environmental pollution and climate change, particularly warming, was mixed, with both additive and synergistic effects commonly reported. Notably, research on behavioural endpoints and the impacts of multiple concurrent stressors remains scarce. This review concludes that climate change, particularly warming, is likely to exacerbate pollution-related pressures on Odonata, potentially resulting in synergistic effects that could accelerate local population declines and increase species' extinction risk.