Biodiversity: Even at ‘safe’ levels, pesticides are having catastrophic impacts on aquatic ecosystems

Dragonflies are taking a big hit from pesticides, even at levels deemed “safe” by lab tests. Bob Berwyn photo.

Study documents dramatic regional decline of insect species

By Summit Voice

SUMMIT COUNTY — After studying ecosystems contaminated with pesticides, scientists say they’ve been able to measure a dramatic loss of invertebrate biodiversity in polluted streams and rivers.

The study is one of the first to document the toxic effects of pesticides at a regional ecosystem level, rather than exptrapolating toxicity from lab tests.

“The current practice of risk assessment is like driving blind on the motorway”, said ecotoxicologist Matthias Liess. “To date, the approval of pesticides has primarily been based on experimental work carried out in laboratories and artificial ecosystems.”

The research looked at areas in Germany, France and Australia to get a global context and a regional perspective. In the European areas, the number of species in polluted rivers and streams dropped by 42 percent; in Australia, by 27 percent.

Stoneflies, mayflies, caddisflies and dragonflies were especially hard-hit. They are particularly susceptible to pesticides and are key species in the aquatic food chain, sustaining fish and birds.

The study results, published in the Proceedings of the National Academy of Sciences, suggests that the threat to biodiversity from pesticides has obviously been underestimated in the past, the researchers said.

The study shows that impact to insects and their ecosystems is catastrophic even at levels deemed safe by existing regulatory schemes, with legally-permitted maximum concentrations that don’t adequately protect the biodiversity of invertebrates in flowing waters.

New concepts linking ecology with ecotoxicology are urgently needed, the scientists said.

“To be able to assess the ecological impact of such chemical substances properly, existing concepts need to be validated by investigations in real environments as soon as possible,” Liess said.

“The latest results show that the aim of the UN Convention on Biological Diversity to slow down the decline in the number of species by 2020 is jeopardized. Pesticides will always have an impact on ecosystems, no matter how rigid protection concepts are, but realistic considerations regarding the level of protection required for the various ecosystems can only be made if validated assessment concepts are implemented,” Liess said.

Scientists involved in the study include: Mikhail A. Beketov and Matthias Liess from the Helmholtz Centre for Environmental Research in Leipzig, together with Ben Kefford from the University of Technology, Sydney and Ralf B. Schäfer from the Institute for Environmental Sciences, Landau.


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