Cleaning up rivers to fight climate change

Reducing river pollution offers “real benefit” against climate change

Plans to spend £3 billion on cleaning up English and Welsh rivers under European legislation will also help in the fight against climate change – this according to new research from Cardiff University and Radboud University in the Netherlands.

The team used laboratory studies and over 40,000 thousand samples from British rivers to show how some aquatic animals are less able to tolerate warmer temperatures in polluted water. 

In the laboratory, mayflies such as the green drake (Ephemera danica) and the blue-winged olive (Serratella ignita) were able to survive temperatures 3-5 °C higher where oxygen was plentiful than when it was reduced. 

Similarly, in English and Welsh rivers, poor oxygenation caused by pollution drastically reduced the occurrence of these species, with the effect especially pronounced in warmer conditions. 

This is the first time that field and laboratory studies have been used in this way to assess how reducing pollution can help to adapt rivers to climate change.

“Cool water insects like many mayflies are in triple jeopardy in warmer, polluted waters,” explained the study’s senior author, Professor Steve Ormerod. 

“First, at higher temperatures, water can hold less oxygen.  Secondly, insects need more oxygen to keep pace with their needs as temperatures increase.  Thirdly, oxygen is used in the breakdown of organic pollution, with this effect occurring most rapidly in warmer waters. 

“These three effects mean that warm polluted waters are the worst combination.”

Professor Ormerod believes that these results could fuel debate about the value of Britain’s EU membership in environmental protection. 

Implementing EU laws such as the Water Framework directive are expensive, he says, yet on this evidence can drive important aspects of environmental improvement and protection as the climate changes. 

Dr Isabelle Durance, Director of Cardiff University’s new Water Research Institute added:

“Our work presents real hope in the fight against climate change. We need to find ways to reduce the future effects of warming, and our data show how regulating and reducing pollution offers real benefit. 

“Our past analysis shows how the recovery from pollution in Britain has been fastest in urban rivers – where warming effects from climate change is often most acute.”

Extensive field data for the study were provided by long-term monitoring by the Environment Agency and Natural Resources Wales. 

The work is published in the leading Journal Global Change Biology.