First posted on 06-21-2013
Pesticides, primarily those used in agriculture, are among the most investigated and most regulated of pollutants. Recent studies have concentrated on the influence of pesticides on the biodiversity of aquatic habitats.
International researchers recently demonstrated biodiversity losses of 27 to 42 percent in streams across the globe as a result of pesticide runoff. Biodiversity refers to the variety of living organisms in a particular habitat.
Most of the loss occurred as groups of animals that were particularly susceptible to pesticides disappeared. Those organisms included species of stoneflies, mayflies, caddisflies, damselflies and dragonflies. All of these invertebrates are crucial to the survival of a stream ecosystem both as feeders that help keep streams clean, and as a food for other animals such as fish and birds.
The diversity of these invertebrates in the nymph or larval stage are important indicators of overall water quality.
Of concern to the research team is that the decline of invertebrates is already occurring at catastrophic levels even with pesticide concentrations considered safe in many parts of the world.
Matthias Liess is a toxicologist and was part of the research team from the Helmholtz Center for Environmental Research. He cautioned, “The current practice of risk assessment is like driving blind on the motorway.” Liess went on to remark that most current legal limits for pesticides are inadequate for biodiversity protection in flowing waters.
Pesticide approval is typically based on experiments carried out in laboratory conditions. Liess advocates validating chemicals based on investigations in real environments.
“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,” according to Leiss. He feels the threat to ecosystems from pesticides has been underestimated in the past.
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