Australasian Science: Australia's authority on science since 1938

Pesticides Are Destroying Aquatic Ecosystems

By Stephen Luntz

Pesticide run-off from agriculture has been blamed for a crisis in aquatic ecosystems despite laboratory studies supporting current regulatory levels.

Dr Ben Kefford of the University of Technology, Sydney measured the decline in aquatic insects in waterways in France, Germany and Victoria and observed the loss of 42% of European species compared with uncontaminated sites. The findings were published in the Proceedings of the National Academy of Sciences.

Kefford and his co-authors established that there was little or no correlation between other possible causes of decline, such as rising salinity, and the loss of species. The team also predicted species whose lifecycle and physiology would make them most vulnerable to pesticides.

“These mainly include representatives of the stoneflies, mayflies, caddisflies and dragonflies, and are important members of the food chain right up to fish and birds,” Kefford says. He found that these were indeed the species most likely to disappear from waterways near high pesticide use.

The Australian end of the study did not measure losses to the species level, but found that 27% of insect families had been lost from the most contaminated Victorian rivers, closely resembling the 30% of families that had disappeared in Europe.

“To date, the approval of pesticides has primarily been based on experimental work carried out in laboratories and artificial ecosystems,” says lead author Dr Mikhail Beketov of the Helmholtz Centre for Environmental Research in Germany. These have guided the legal pesticide limits used in Europe that Beketov and Kefford’s fieldwork indicates is inadequate.

“It may be that there are safer varieties of pesticide available,” Kefford says, “but the nastier ones are no longer permitted. The ones in use are those that seemed acceptable in lab studies. We need more studies in the field.”

Another possibility Kefford raises is to increase the use of vegetated buffers around streams to prevent bursts of pesticides entering them after heavy rains.