Brown streams a 'triumph'
Some streams in the UK are becoming murkier
Also In The News
|
Directed by Kenneth Branagh, screenplay by Harold Pinter, out November 17th, starring Jude Law and Michael Caine, running time 90 minutes. |  |
Thursday, 22, Nov 2007 01:49
Streams running with brown water rather than clear may not look as pleasant but scientists say an increase in murky-coloured waters should be celebrated.
Over the last 20 years streams and lakes in remote parts of the UK, southern Scandinavia and eastern North America have become increasingly stained brown.
A study into the shift in colour, published today in the journal Nature, says it is a result of dissolved organic matter and is indicative of a return to a more natural, pre-industrial state following a decline in the level of acid rain.
Researchers led by University College London (UCL) studied over 500 sites across the northern hemisphere and analysed trends in dissolved organic carbon, air temperatures and a number of other chemical variables.
"We've found that the dominant factor in the whole process is not global warming," said John Stoddard from the US Environmental Protection Agency.
"The most important driver has actually been the major reduction in acid rain since the 1970s. As acidity and pollutant concentrations in the soil fall, carbon becomes more soluble, which means more of it moves into our lakes and rivers and more can be exported to the oceans."
Don Monteith, senior research fellow at the UCL environmental change research centre, added: "A huge amount of carbon is stored in the form of organic deposits in soils, and particularly in the peatlands that surround many of our remote surface waters.
"In the past two decades an increasing amount of this carbon has been dissolving into our rivers and lakes, turning the water brown."
The researchers concluded that more research is needed to study the implications for freshwaters.