The Wandle in south London was officially designated an open sewer in the 1960s. After serious efforts by government, water companies and conservation groups to clean it, the river today is teeming with life, as Theo Pike, chair of the environmental nonprofit Wandle Trust records. Scroll down for photograph of volunteers at work.
Pilita Clark, the FT’s environment correspondent, reports on a 21-year study published in the Global Change Biology journal (26th May). It found that in the period 1991-2011 more than 2,300 rivers and tributaries, from the Thames in the south to the Tyne in north, snails, mayflies and other small creatures have become far more prevalent in previously polluted waters.
Because temperatures in Britain’s rivers have risen 1-2 degrees Celsius on average over the past 20 years, the findings surprised author/researchers Dr Ian Vaughan and Professor Steve Ormerod, from Catchment Research Group, Cardiff School of Biosciences.
They thought the benefits of cleaning up city rivers might have been offset by problems caused by climate change. As waters warm, there is a decline in the oxygen supplies that many species need to thrive. However, 40 of the 78 types of small invertebrates they studied have become more widespread, despite their warmer habitats, as cities have cleaned up the run-off allowed into rivers – but the prevalence of 19 types of animal typically found in dirtier waters has shrunk.
The study’s lead author, Dr Ian Vaughan, said: “It seems that efforts over the last two to three decades to clean up pollution from sewage and other sources have allowed many of these sensitive organisms to expand their range.”
Professor Steve Ormerod added, “The bigger lesson here is that if we manage other stresses on the environment, there is just a chance we could be able to lessen the impact of climate change.”