Researchers from the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, working together with colleagues from Australia and the United States, have suggested that commonly used pesticides may be having a greater impact on aquatic life than has previously been thought.

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Pesticides commonly used in Europe and Australia are reducing the diversity of invertebrate creatures in streams and rivers by up to 42 percent, the researchers said on Tuesday, following the publication of their study in the Proceedings of the US Academy of Sciences (PNAS).

The researchers analysed the impact of insecticides and fungicides, on the regional biodiversity of invertebrates in streams and rivers (flowing waters) in Germany, France and Australia. The researchers claimed theirs is a landmark investigation into the effects of plant protection products on regional biodiversity; they said they were driven to conduct the research because "The biodiversity crisis is one of the greatest challenges facing humanity, but our understanding of the drivers remains limited."

UFZ researchers Mikhail A. Beketov and Matthias Liess explained that, although agricultural pesticides are amongst the most well-investigated and regulated groups of common pollutants, until now, scientists did not know whether, to what extent, or even at what concentrations their use can affect biodiversity (the variation of life-forms within a certain ecosystem).

Study results show inadequacies in current risk assessment strategies

The regions studied by the international team were the Hildesheimer Boerde near Braunschweig, Germany, southern Victoria in Australia and Brittany, France. Their investigation demonstrated "considerable losses in the regional biodiversity of aquatic insects and other freshwater invertebrates" in all regions. In Europe, a 42 percent difference was identified between the biodiversity of non-contaminated regions and strongly-contaminated, comparable areas; in Australia, the difference was 27 percent.

The researchers also discovered that the overall decrease in biodiversity is primarily due to the disappearance of several groups of species that are especially susceptible to pesticides. These mainly include species of stonefly, mayfly, caddisfly, and dragonfly. They are all important members of the food chain, supporting fish and birds.

The researchers said the species affected are particularly good indicators of water quality, and that their loss is a major blow for biological diversity in such aquatic environments.

Furthermore, UFZ scientists warned, "the impact of pesticides on these tiny creatures is already catastrophic at concentrations which are considered [benign] by current European regulation." They found impacts on both species richness and diversity within species, even when chemicals were detected within legally permitted concentrations.

The researchers reiterated that, according to their findings, pesticide use is an important driver of biodiversity loss and declared that "the current ecological risk assessment of pesticides falls short of protecting biodiversity". They called for the development of "new [risk assessment] approaches, linking ecology and ecotoxicology."

Matthias Liess, one of the study's lead authors elaborated, "The current practice of risk assessment is like driving blind on the motorway. To date, the approval of pesticides has primarily been based on experimental work carried out in laboratories and artificial ecosystems. 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."

Speaking plainly, Dr Liess added that his results suggest the risks presented by pesticides to certain ecosystems have been underestimated. He said, "The aim of the UN Convention on Biological Diversity to slow down the decline in the number of species by 2020 is jeopardised. 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 assessment [is effective]."