Forest Fallout

Mountain pine beetles have decimated huge swaths of forest in the West. Now researchers have found that the pests’ attack also has lowered water quality in Colorado.

Climate change has brought more drought and warmer winters to the Rocky Mountains, helping the beetles infest millions of acres of lodgepole pines. The trees’ deaths have caused widespread changes in the forest, such as increasing erosion and soil moisture. Those conditions in turn can alter the levels of organic matter in water and encourage harmful disinfection byproducts to accumulate.

The team studied water quality data from five water treatment plants at Colorado sites that had been severely infested, averaging 3 killed trees per hectare. The researchers then compared the measurements to data from four Colorado plants with only 0.8 killed trees per hectare.

The highly-infested sites had more organic matter in their water and almost ten times more disinfection byproducts, including higher levels of potential carcinogens called trihalomethanes (THMs), the researchers report in Nature Climate Change. The organic matter and THM concentrations appeared to increase after 2008.

The results show that climate change can trigger a chain of events that ultimately affect water quality in the area, the authors say. Researchers will have to wait and see what happens as new plants grow in the forests and fallen trees decay. Roberta Kwok | 31 October 2012

Source: Mikkelson, K.M. et al. 2012. Water-quality impacts from climate-induced forest die-off. Nature Climate Change doi: 10.1038/nclimate1724.

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