Last updated May 31, 2018 at 1:04 pm
We can’t ignore those that don’t always flow.
Credit: iStock
Rivers that sometimes stop flowing and even dry up completely still have a significant impact on CO2emissions around the globe, according to a collaborative study involving 94 international partners.
In fact, the researchers say we may have to increase estimates of daily carbon dioxide emissions from inland watercourses by as much as 150 per cent.
Dusty, dry riverbeds accumulate leaves, wood and other plant material, and this is fine while they stay dry. However, when water starts flowing again it significantly speeds up the microbial breakdown of this plant matter and the release of CO2.
The researchers suggest these intermittent rivers could represent half of the world’s river network and, in response to climate change and increasing water demands, may come to dominate the landscape in some regions.
212 rivers in 22 countries
The project, which was led by France’s National Research Institute in Science and Technology (IRSTEA), quantified and analysed the plant litter deposited along the dry beds of 212 rivers in 22 countries, including several in Australia and New Zealand.
Sub-samples of leaf litter were analysed following standardised assays to simulate short-term (24-hour) rewetting events. High respiration rates were measured, reflecting the reactivation of microbial communities within the litter.
In turn, this activity released substantial quantities of CO2. A rough extrapolation indicates that estimates of daily CO2emissions from inland watercourses could rise by between 7 and 152 per cent if data from intermittent rivers are added to existing data from perennial rivers. One rewetting event could contribute up to 10 per cent of this increase.
The researchers say their results highlight the need to incorporate intermittent river ecosystems into further studies exploring the contribution of inland waters to carbon cycling at the global scale.
The paper published in Nature Geoscience.
