Deteriorated rivers breathe out greenhouse gases
Rivers and streams have been found to release up to 3.9 billion tonnes of carbon annually1. Whereas carbon emission from rivers is a natural ecosystem process, the emission rates can be significantly increased by human-induced degradation of rivers. This problem is especially pronounced for urban rivers. A study from the Cuenca urban river system in Ecuador showed, for instance, a clear relationship between pollution status and greenhouse gas emissions, and the global warming potential of heavily polluted rivers was up to ten times higher than that of rivers with acceptable water quality2. Similarly, a study of rivers in Hong Kong showed that emissions of carbon dioxide, methane, and nitrous oxide were 2.2, 1.5 and 4.0 times higher, respectively, from polluted rivers than from those in better condition3.
A consequence of such findings is that the protection and restoration of rivers could significantly decrease emissions of greenhouse gases from these water bodies. In the EU, the implementation of river restoration programmes as part of the European Green Deal, the Water Framework Directive and the EU Biodiversity Strategy for 2030 is vital in order to improve the state of European rivers. The urgency of such measures was recently highlighted in a scoping paper by the Living Rivers Europe Coalition4, which builds on a position paper by more than 20 NGOs in Europe.
3. See https://www.bbc.com/future/article/20210323-climate-change-the-rivers-that-breathe-greenhouse-gases, which was the main source of information for this text