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Pesticides Tied To Reduced Biodiversity In Streams And Rivers

A new study of water habitats in Europe and Australia, that for the first time examines the effect of pesticides on regional biodiversity, concludes pesticide use significantly reduces regional biodiversity of invertebrates in streams and rivers, in some areas by as much as 42%. The researchers say it is time to find new ways to look at how pesticide use affects the natural environment.

The study team includes members from Helmholtz Centre for Environmental Research (UFZ) in Leipzig, the Institute for Environmental Sciences Landau, both in Germany, and the University of Technology in Sydney, Australia. They write about their findings in the 17 June online issue of the Proceedings of the US Academy of Sciences (PNAS).

Pesticides, such as as insecticides and fungicides used in agriculture, are some of the most regulated environmental pollutants.

But despite this, little is known about their impact on the biodiversity of water environments like rivers and streams, and in particular, the levels at which they begin to have an effect. Study Compared Biodiversity of Streams to Amount of Pesticide Contamination For their study, Mikhail Beketov, an aquatic ecologist, and Matthias Liess, an ecotoxicologist, both from the Helmholtz Centre in Leipzig, and colleagues, analyzed data from Europe and Australia to assess the effect of pesticides on the regional diversity of invertebrates in rivers and streams.

They gathered data on 16 streams in Brittany in France, 23 streams in the Hildesheimer Boerde near Braunschweig in Germany, and 24 in southern Victoria in Australia. The data allowed them to analyze pesticide levels against bidiversity in terms of the numbers of different aquatic species in the different regions.

They categorized the biodiversity of the streams according to the level of pesticide contamination: uncontaminated, slightly contaminated and highly contaminated.

The results showed that in both Europe and Australia, there were considerable differences in biodiversity between regions of high pesticide contamination and regions with no contamination. In Europe, the difference was as much as 42% difference in biodiversity; in Australia it was 27%.

When they looked in more detail at the species that were absent in the more polluted areas, they found they were mainly ones known to be sensitive to pesticides, such as stoneflies, caddisflies, mayflies, and dragonflies.

These sensitive species are also important members of a food chain that leads to fish and birds. Current Measures Are Failing to Protect Biodiversity The researchers were disturbed to find that this severe loss of biodiversity is happening at pesticide levels deemed safe under current European legislation.

Describing use of pesticides as a driver of biodiversity loss, they say their results show the currently permitted levels are not adequately protecting the biodiversity of invertebrates in flowing waters.

They say new approaches as urgently needed to look more closely at the links between "ecology and ecotoxicology".

In a press statement, Liess says the current ways of assessing risks that pesticides pose to biodiversity is "like driving blind on the motorway". Pesticide Risk Assessment Models Should Be Tested In Real Environments Pesticides currently gain approval based on evidence from experimental work done in labs and artificial ecosystems.

To get realistic estimates of pesticide impact on the environment, the existing models should be validated in real environments. This should be done as soon as possible, says the team.

Failure to do so will jeopardize the aim of the UN Convention on Biological Diversity to slow down the decline in the number of species by 2020, says Liess.

While human subjects did not feature in this particular study, there is evidence to suggest that pesticide exposure affects us too, and in ways we may not readily be aware of.

For instance, in a recent analysis of over 100 studies from around the world, researchers in Italy suggest exposure to pesticides and solvents is linked to a higher risk of developing Parkinson's disease.

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