Whenever we talk about the increasing greenhouse emission in the world, we are quick to point our finger at the fossil fuels, transportation, and agriculture. However, the latest study conducted by the researchers at the Washington State University revealed that a silent climate change culprit is lurking amidst us unnoticed: the dams!
After 15 years of study, the researchers found that more than one giga-tonnes of carbon dioxide is annually added to the atmosphere by the reservoirs all over the globe. This figure is higher than the greenhouse emission of Canada.
The discovery leads us to one important question: why is the greenhouse emission phenomenon observed only in human-made reservoirs? Why is the same not depicted by the natural water bodies? The answer lies in the underlying process that leads to the construction of the artificial water bodies. Unlike a natural body of water, the building of a water reservoir often leads to flooding of soil rich in organic matter. On decomposition, the vegetation and organic nutrients are converted into methane, carbon dioxide, and nitrous oxides.
The latest research concluded that the emissions from the water reservoirs make 1.3 percent of the global emissions. Another finding that surprised Bridget Deemer, the research associate at the Washington State University, concerned methane and its impact on the climate change.
“We had a sense that methane might be pretty important but we were surprised that it was as important as it was. It’s contributing right around 80 percent of the total global warming impact of all those gases from reservoirs. It’s a pretty important piece of the budget.”
Albeit the lower atmospheric concentration of methane, it traps gas much more efficiently than carbon dioxide. Thus, the impact of methane is more significant than the CO2 that outweighs it.
“Methane is less soluble in water than are the other greenhouse gases included in this study (carbon dioxide and nitrous oxide). Because of this, a large fraction of methane emission can occur as bubbles. If these bubbles aren’t captured by measurements, reservoir methane flux can be underestimated.”
However, the future is not as bleak as it seems. In fact, the researchers reassured that these findings would help the humans to come up with better plans for the water reservoirs to reduce the overall carbon footprint.
“Because reservoirs are human designed and human operated, there may be an opportunity for greenhouse gas mitigation at both the planning and the operation stages. The results of our study suggest that reservoirs sited in locations downstream of ‘nutrient’ inputs will produce more methane than those receiving fewer nutrient inputs. It is also possible that reducing nutrient inputs to existing reservoirs could reduce methane emissions, but this remains to be tested in the field.”
The study will be published in the BioScience journal and will be the most comprehensive research conducted on the topic till date.