Scientists find agricultural soil erosion acts like a 'carbon sink'
A great number of human activities is being scrutinized to find out whether they contribute to climate change. From damming rivers to deforestation, the quest is on to study the impacts of these interactions with nature through the spectrum of global warming. Luckily not all of man's actions contribute to the problem. A major process that is bad enough as it is - soil erosion caused by agriculture - is not a source of carbon dioxide to the atmosphere. On the contrary, it acts like a mild 'carbon sink'. This is the (surprising) finding of research published today in the journal Science. The study was carried out by an international team of researchers from the University of California Davis, the Catholic University of Leuven in Belgium, and the University of Exeter in the U.K.
The results of the research are important in the context of energy farming, because to calculate the carbon balance of bioenergy accurately one has to take into account all changes to the carbon cycle during the entire production chain, including potential indirect emissions arising from agriculture. Farming can both cause and combat soil erosion.
Carbon emissions are of great concern worldwide because together with other greenhouse gases they trap heat in the Earth's atmosphere and are a major cause of global climate change. But for a whole range of natural processes and human activities the research is ongoing.
Erosion, therefore, creates what can be described as a 'sink' of atmospheric carbon. The team improved previous estimates of the amount of carbon being sunk.
energy :: sustainability :: biomass :: bioenergy :: biofuels :: agriculture :: soil erosion :: carbon cycle :: carbon sink ::
In other words, erosion captures the equivalent of about 1.5 percent of annual fossil-fuel emissions worldwide. Earlier studies suggested a broad range of erosion's effects, from a sink equaling 10 percent of fossil-fuel emissions, to a source equaling 13 percent.
But even without major carbon impacts, the researchers said, erosion is a problem that must be addressed, because it has a detrimental effect on agricultural productivity and the surrounding environment.
Funding for the study was provided by the University of California's Kearney Foundation of Soil Science, the European Commission under the Marie Curie IntraEuropean Fellowship Programme, and the Fund for Scientific Research, Flanders.
Image: severe soil erosion brought about by animals overgrazing and vegetation being cleared in Kenya. Credit: Photo Researchers.
References:
K. Van Oost, et al., "The Impact of Agricultural Soil Erosion on the Global Carbon Cycle", Science, 26 October 2007, Vol. 318. no. 5850, pp. 626 - 629, DOI: 10.1126/science.1145724.
UC Davis: Agricultural Soil Erosion Is Not Adding to Global Warming - October 25, 2007.
The results of the research are important in the context of energy farming, because to calculate the carbon balance of bioenergy accurately one has to take into account all changes to the carbon cycle during the entire production chain, including potential indirect emissions arising from agriculture. Farming can both cause and combat soil erosion.
Carbon emissions are of great concern worldwide because together with other greenhouse gases they trap heat in the Earth's atmosphere and are a major cause of global climate change. But for a whole range of natural processes and human activities the research is ongoing.
There is still little known about how much carbon exactly is released, versus captured, by different processes in terrestrial ecosystems. We urgently need to quantify this if we are to develop sensible and cost-effective measures to combat climate change. - Johan Six, professor of agroecology at UC DavisIn their new study, the researchers found that erosion acts like a conveyor belt, excavating subsoil, passing it through surface soils and burying it in hollows downhill. During its journey, the soil absorbs carbon from plant material; when the soil is buried, so is the carbon.
Erosion, therefore, creates what can be described as a 'sink' of atmospheric carbon. The team improved previous estimates of the amount of carbon being sunk.
Some academics have argued that soil erosion causes considerable emissions of carbon, and others that erosion is actually offsetting fossil-fuel emissions. Now, our research clearly shows that neither of these is the case. - Kristof Van Oost, lead author, Catholic University of LeuvenBy using caesium-137 and carbon inventory measurements from a large-scale survey, the scientists found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, they estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year resulting from erosion in the world's agricultural landscapes:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: agriculture :: soil erosion :: carbon cycle :: carbon sink ::
In other words, erosion captures the equivalent of about 1.5 percent of annual fossil-fuel emissions worldwide. Earlier studies suggested a broad range of erosion's effects, from a sink equaling 10 percent of fossil-fuel emissions, to a source equaling 13 percent.
But even without major carbon impacts, the researchers said, erosion is a problem that must be addressed, because it has a detrimental effect on agricultural productivity and the surrounding environment.
Funding for the study was provided by the University of California's Kearney Foundation of Soil Science, the European Commission under the Marie Curie IntraEuropean Fellowship Programme, and the Fund for Scientific Research, Flanders.
Image: severe soil erosion brought about by animals overgrazing and vegetation being cleared in Kenya. Credit: Photo Researchers.
References:
K. Van Oost, et al., "The Impact of Agricultural Soil Erosion on the Global Carbon Cycle", Science, 26 October 2007, Vol. 318. no. 5850, pp. 626 - 629, DOI: 10.1126/science.1145724.
UC Davis: Agricultural Soil Erosion Is Not Adding to Global Warming - October 25, 2007.
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