In the first study of its kind to examine the long term, continuous impact of urbanisation on carbon production in our waterways, researchers from the University of Bristol have found population increase is more closely correlated to rising levels of Dissolved Organic Carbon (DOC) than previously thought. This has major implications for the future of aquatic wildlife and ecosystems and for the management of water treatment processes at a time of increased urbanisation.
Researchers in Civil Engineering considered more than 20,000 samples of water colour and Dissolved Organic Carbon (DOC) concentration from the Thames River between 1884 and 2014, to find that DOC levels doubled in the space of 130 years, from 1.7mg/L to 4.3mg/L.
Whereas previous studies focused on shorter time periods and rural basins, this particular study looked at the Thames basin over a critical period covering intense industrialisation and urbanisation, as well as both World Wars, which saw grasslands converted for agricultural production.
Urbanisation increased by a factor of 2.5, while the population quadrupled, causing a dramatic hike in the quantity of carbon entering the river due to sewage effluents.
During the same period, between 63 and 89% of the DOC released from the terrestrial biosphere was lost from the river (which equates to 26,800 metric tonnes), part of it emitted into the atmosphere.
Lead researcher Valentina Noacco said:
“We now know that population increase was the biggest cause of riverine carbon increase during this period. This has implications at a global level because the majority of the world population now lives in cities, and that is only going to increase, so we need to consider how we can use nature-based measures to mitigate against the likelihood of future carbon release.
“It may be necessary to reduce agricultural activities in sensitive basins, while also restoring grasslands and creating more buffer zones that can help minimise the human impact.”
Investigators
- Dr Valentina Noacco, Department of Civil Engineering, University of Bristol
- Prof Thorsten Wagener, Department of Civil Engineering, University of Bristol
- Dr Nicholas Howden, Department of Civil Engineering, University of Bristol
Collaborators
- Prof Fred Worrall, Department of Earth Sciences, Durham University
- Prof Tim Burt, Department of Geography, Durham University
Funders
Natural Environment Research Council (NERC)