Rivers have the ability to bounce back to health from years of pollution, offering hope for rivers worldwide, according to the results of a new Victorian study.

 

Melbourne University researchers Vincent Pettigrove and Bryant Gagliardi studied the rivers in the Ovens Valley, north east Victoria, which had been polluted with pesticides from 150 years of tobacco farming.

 

They found that by examining the mouthparts of a common river insect, the non-biting midge, or 'chironomid', they could ascertain whether pesticides — for example DDT, a now-banned carcinogenic toxin — were present in the river. Deformities included missing, additional or fused 'teeth'. The researchers said that insect deformity can be a cheaper measure of river health than traditional chemical analysis and can assist agriculture in managing land more sustainably.

 

The Oven's River Basin is located in the Murray Darling catchment. Tobacco cultivation occurred from the 1850s and peaked during the 1970s. The use of pesticides such as DDT were banned in Victoria in 1981, and, after years of declining profit margins, the industry completely closed in 2006.

 

The study examined midge larvae at tobacco sites, in 1988 and again in 2010, as well as sites 10km upstream and downstream, to see changes over time. The 1988 research showed a significantly higher amount of deformities in the larvae collected at the tobacco sites compared with upstream and downstream samples. But in 2010, the amount of deformities was not significantly different between the different locations.

 

The results in the Ovens Valley showed that improved farming practices can significantly improve the health of local rivers within a short space of time. The findings could be used to help rivers worldwide.

 

The findings were published in the journal Agriculture, Ecosystems and Environment.