Neonicotinoids disrupt aquatic food webs and decrease fishery yields

Science ‘Cascading effects of pesticide use

It is now well known that neonicotinoids negatively affect pollinators. As research has expanded, it has become clear that these globally used insecticides directly affect other ecosystem components, including vertebrates. Yamamuro et al. now show that these compounds are indirectly affecting species through trophic cascades (see the Perspective by Jensen). Since the application of neonicotinoids to agricultural fields began in the 1990s, zooplankton biomass has plummeted in a Japanese lake surrounded by these fields. This decline has led to shifts in food web structure and a collapse of two commercially harvested freshwater fish species. The authors argue that such dynamics are likely occurring widely.

Invertebrate declines are widespread in terrestrial ecosystems, and pesticide use is often cited as a causal factor. Here, we report that aquatic systems are threatened by the high toxicity and persistence of neonicotinoid insecticides. These effects cascade to higher trophic levels by altering food web structure and dynamics, affecting higher-level consumers. Using data on zooplankton, water quality, and annual fishery yields of eel and smelt, we show that neonicotinoid application to watersheds since 1993 coincided with an 83% decrease in average zooplankton biomass in spring, causing the smelt harvest to collapse from 240 to 22 tons in Lake Shinji, Shimane Prefecture, Japan. This disruption likely also occurs elsewhere, as neonicotinoids are currently the most widely used class of insecticides globally. Click here access the paper

The Guardian report on this work Common pesticides found to starve fish ‘astoundingly fast’ by killing aquatic insects    Damian Carrington Environment editor

The Silent Spring prophecy that pesticides could “still the leaping of fish” has been confirmed, according to scientists investigating the collapse of fisheries in Japan. They say similar impacts are likely to have occurred around the world. The long-term study showed an immediate plunge in insect and plankton numbers in a large lake after the introduction of neonicotinoid pesticides to rice paddies. This was rapidly followed by the collapse of smelt and eel populations, which had been stable for decades but rely on the tiny creatures for food. The analysis shows a strong correlation but cannot prove a causal link between the insecticides and the collapse. However, independent scientists said other possibilities had been ruled out and that the work provided “compelling evidence”.   Click here to read more