Their study, the first of its kind in the world, found pesticides caused wide scale species loss even when they were used legally. “Ecological risk assessment of pesticides falls short of protecting biodiversity,” they report today in the journal Proceedings of the National Academy of Sciences.
Co-author Ben Kefford, of the University of Technology, Sydney, said regulations governing the use of pesticides were based on studies in laboratories or “semi-natural” settings such as simulated river sections. “They’re not doing any studies in the real world,” he said.
Dr Kefford said the species most affected included mayflies, stoneflies, cattus flies and dragonflies. He said aquatic invertebrates were an important food source for “fish, birds, platypus and the like” as well as being critical to the healthy functioning of streams.
“This is an area of species loss which is essentially being ignored. You can see habitat modification or invasive species just by looking. Pesticides are not something you can see with the naked eye. You have to do complex chemical analysis to work out what’s in the water.”
Dr Kefford said pesticides caused environmental harm in “pulses” when currents funnelled them into particular locations, raising concentration levels. The species most at risk were those that reproduced slowly or couldn’t relocate easily.
“If you’ve got a life cycle of a few weeks, even if your population is drastically reduced by pesticide contamination, the population can recover within a few months. But some organisms last six months, 12 months, even two years. Even if a very occasional pesticide pulse comes down, they will be most affected.”
He said pesticide regulations needed to be informed by real field studies, backed up by regular monitoring. “You could never monitor every creek, but you need some targeted studies where you check whether they are an issue.”