- If left to its own devices, this carbon-rich water remains below ground for hundreds to thousands of years before surfacing in oceans or freshwater bodies. But humans are now extracting groundwater at an unprecedented pace to sustain a growing population
November 16, 2017 American Geophysical Union Read full ScienceDaily article here
Humans may be adding large amounts of carbon dioxide to the atmosphere by using groundwater faster than it is replenished, according to new research. This process, known as groundwater depletion, releases a significant amount of carbon dioxide into the atmosphere that has until now been overlooked by scientists in calculating carbon sources, according to the new study.
The study’s authors estimate groundwater depletion in the United States could be responsible for releasing 1.7 million metric tons (3.8 billion pounds) of carbon dioxide to the atmosphere every year.
Based on these figures, groundwater depletion should rank among the top 20 sources of carbon emissions documented by the US Environmental Protection Agency (EPA) and the Intergovernmental Panel on Climate Change (IPCC). This would mean the carbon dioxide emitted through groundwater depletion is comparable to the carbon generated from aluminum, glass, and zinc production in the United States, according to the study’s authors….
…Rain falling from the sky contains the same amount of carbon dioxide as is present in the atmosphere. But soil carbon dioxide levels are up to 100 times greater than carbon dioxide levels in the atmosphere, because soil microbes degrade organic carbon into carbon dioxide. When rainwater hits the ground and percolates through Earth’s rocks and sediments, the water dissolves extra carbon produced by these microbes.
If left to its own devices, this carbon-rich water remains below ground for hundreds to thousands of years before surfacing in oceans or freshwater bodies. But humans are now extracting groundwater at an unprecedented pace to sustain a growing population….
…Groundwater depletion’s impact on carbon emissions is significant yet relatively small compared to the leading contributors, according to the authors. For example, scientists estimate fossil fuel combustion in the United States is responsible for releasing more than 5 billion metric tons (11 trillion pounds) of carbon dioxide into the atmosphere every year, close to 3,000 times the amount released from groundwater depletion. Still, the study authors argue that understanding all sources of carbon dioxide emissions is important for making accurate climate change projections and finding solutions….
Warren W. Wood, David W. Hyndman. Groundwater Depletion: A Significant Unreported Source of Atmospheric Carbon Dioxide. Earth’s Future, 2017; DOI: 10.1002/2017EF000586