06
Nov
Neonicotinoid Insecticides Deprive Fish of Food in Lake Shinji, Japan
(Beyond Pesticides, November 6, 2019) Between 1981 and 1992, Japanese fishers annually reaped an average of 240 tons of smelt from Lake Shinji. After 1993, their nets turned up about 22 tons – a 90% drop in their yield. Eel catches dropped by 74%. New research, published in the journal Science, implicates the introduction of neonicotinoids to the abutting watershed in the decimation of these aquatic populations, stating, “In Lake Shinji, neonicotinoids indirectly reduced fishery yields by decreasing the abundance of invertebrates that serve as food for smelt and eels.”
Researchers analyzed decades of data on zooplankton, midges, and water quality as well as annual fishery yields of eel and smelt spanning from 1981-2014. Zooplankton biomass, an important fodder for smelt, plummeted from 108 µg C L−1 to 18.2 µg C L−1 after imidacloprid was introduced for use on rice paddies in May of 1993. Midges (Cyathura muromiensis) that were found in abundance in 1982 totally disappeared from all sample sites by 2016. While the smelt and eel populations drastically declined, the authors note that icefish, which eat a more diversified diet, were not impacted. Though researchers considered the possibilities of other influencing factors such as invasive species, hypoxia, and changes in fish stocking, they did not relate to the observations.
“This study, although observational, presents compelling evidence,” Professor Olaf Jensen, PhD of Rutgers University, a scientist unaffiliated with the study, told The Guardian, “A fishery that was sustainable for decades collapsed within a year after farmers began using neonicotinoids. This is a large and astoundingly fast response.”
This research provides yet another illustration of how pesticides cause ripple effects through ecosystem structures; an ecological phenomenon known as a trophic cascade. Drew Toher of Beyond Pesticides notes in “Pesticide Use Harming Key Species Ripples through the Ecosystem” that, “In both still and fast-moving aquatic environments, pesticides act powerfully on the foundational levels of the food web.”
Trophic cascades are not limited to aquatic environments, of course. As an avian example, French researchers recently pointed to the decline of insects (estimated at about -80%) as the main cause for the dramatic collapse of bird species in their countryside over the last decade – declines measured at over a third, and in some cases two-thirds.
Rachel Carson sparked monumental change in the 1960’s as she called out the role of toxic pesticides in ecosystem collapse with her seminal work, Silent Spring. Despite the positive influence her work had on illuminating the problem of environmental contaminants, her ominous predictions are being invoked in observational research. Yamamuro et al. end their paper with a reference to Carson, “She wrote: ‘These sprays, dusts and aerosols are now applied almost universally to farms, gardens, forests and homes – nonselective chemicals that have the power to kill every insect, the ‘good’ and the ‘bad’, to still the song of birds and the leaping of fish in the streams.’ The ecological and economic impact of neonicotinoids on the inland waters of Japan confirms Carson’s prophecy.”
There is plenty of evidence that toxic pesticides are causing cascading crises and plunging us into a future devoid of the richness that unpolluted ecosystems offer. We stand, as Carson once said, at a crossroad. Beyond Pesticides continues to advocate for organic farming as a healthy and economically viable alternative for people and the planet. While chemical-intensive agriculture is currently a major driver of biodiversity loss worldwide, organic practices can, conversely, bolster wild populations.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Science
