Warming rivers make marked contribution to global greenhouse gas levels

Warming streams and rivers could be disproportionately contributing to greenhouse gas emissions.

Warming streams and rivers could be disproportionately contributing to the amount of planet-warming greenhouse gases, according to a new study.

Many such watercourses with high levels of fine sediment and organic materials building up in their streambeds could be increasing greenhouse gas emissions from rivers, as well as increasing the risk of communicable disease and putting wildlife at risk.

Rising river temperatures are anticipated globally because of climate change and this will be made worse by increasing abstraction of cool groundwater that helps to reduce high temperatures in summer.

Researchers from the University of Birmingham and the British Geological Survey have discovered that warming rivers can cause marked increases in carbon dioxide and methane production.

Publishing findings in Nature Communications, their comparison of potential greenhouse gas emissions from UK streambed sediments shows that sensitivity to temperature varies with geology, organic matter and sediment size.

It is expected that temperature increases will be particularly important in agricultural lowland rivers and streams representing large areas of Europe, North America and Asia.

University of Birmingham co-lead researcher Sophie Comer-Warner said: “Our findings highlight the substantial risk of future greenhouse gas emissions from warming rivers, especially those which are small but have high organic matter concentrations.

“Under future climate-warming scenarios and changes in land use leading to more organic matter ending up in warmer rivers, the emission of greenhouse gases from such watercourses could increase disproportionately relative to their size in the landscape.”

Small rivers are known to have the highest rates of greenhouse gas emissions, with relatively large concentrations of carbon dioxide and methane found in their sediments. There has been little previous research into the origin and changing composition of these sediments and how this impacts greenhouse gas production.

University of Birmingham co-lead author Paul Romeijn commented: “Our comparison of potential greenhouse gas emissions from UK streambed sediments revealed levels of carbon dioxide and methane that were especially raised in chalk rivers, such as the River Lambourn in the North Wessex Downs, and in sediments rich in small particles and organic matter.

“If we are serious about reducing future emissions from rivers under climate warming, land management attention needs to focus on reducing sediment rich in organic matter content, and decreasing groundwater abstraction.”

ENDS

For more information or interviews, please contact Tony Moran, International Communications Manager, University of Birmingham on +44 (0) 121 414 8254 or +44 (0)782 783 2312. Out-of-hours +44 (0)7789 921165.

Notes to Editors

  • The University of Birmingham is ranked amongst the world’s top 100 institutions, its work brings people from across the world to Birmingham, including researchers and teachers and more than 6,500 international students from over 150 countries.
  • ‘Thermal sensitivity of CO2 and CH4 emissions varies with streambed sediment properties’ is published in Nature Communications. It was written by Sophie A. Comer-Warner, Paul Romeijn, Daren C. Gooddy, Sami Ullah, Nick Kettridge, Benjamin Marchant, David M. Hannah and Stefan Krause. Read the paper.
  • The British Geological Survey (BGS), a component body of the Natural Environment Research Council (NERC), is the nation's principal supplier of objective, impartial and up-to-date geological expertise and information for decision making for governmental, commercial and individual users. The BGS maintains and develops the nation's understanding of its geology to improve policy making, enhance national wealth and reduce risk. It also collaborates with the national and international scientific community in carrying out research in strategic areas, including energy and natural resources, our vulnerability to environmental change and hazards, and our general knowledge of the Earth system. More about the BGS.
  • The Natural Environment Research Council is the UK's main agency for funding and managing world-class research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, food security, environmental influences on human health, the genetic make-up of life on earth, and much more. NERC receives around £300 million a year from the government's science budget, which it uses to fund research and training in universities and its own research centres.
  • Part of the project funding comes through the EU Marie Curie Initial Training Network – an initiative aimed at driving scientific excellence and innovation; bringing together universities, research institutes and other sectors from across the world to train researchers to doctorate level.