Is erosion an effect of aging



10.04.2017 17:00

Climate change: unimagined role of soil erosion

Johannes Seiler Department 8 - University Communication
University of Bonn

The study by a research group from Belgium, Germany and Switzerland with the collaboration of scientists from the universities in Bonn and Augsburg shows a previously neglected feedback link between the long-term effects of man-made deforestation and soil displacement on global greenhouse gas emissions since the beginning of human agriculture. Around 40 percent of all carbon emissions resulting from the conversion of grassland or forest into arable land are bound in sediments. The surprising results have now been published in the journal “Nature Climate Change”. ATTENTION BLOCKING PERIOD: Do not publish before Monday, April 10th, 5 p.m. CEST!

Since the beginning of agriculture around 8000 years ago, humans have been influencing the global carbon cycle and thus the production of greenhouse gases through extensive deforestation and the associated changes in ecosystems and soils. "Historically, the focus of previous research on arable land use and its effects on soils was largely on the aspects of soil fertility and soil erosion," says first author Dr. Zhengang Wang from the Université catholique de Louvain (UCL) in Belgium. "The fact that soil erosion also creates carbon-rich sediments and that a large part of the eroded carbon can be replaced by photosynthesis in plants and returned to the soil was often ignored," adds last author Prof. Kristof van Oost from der UCL.

"The reason for this is not an intentional omission of this knowledge, but the fact that erosion studies often only extend over short measuring periods, while sedimentation and soil formation processes have to be considered on much longer time scales," adds private lecturer Dr. Thomas Hoffmann from the University of Bonn. For this reason, there have so far been no global studies that consider both sides of the coin on the soil carbon balance together: on the one hand, the release of carbon dioxide through deforestation and erosion and, on the other hand, the retention of carbon through sediment formation in soils. These two opposing processes make it extremely difficult to estimate the long-term effects of agriculture on the release of the greenhouse gases carbon dioxide, nitrogen oxides and methane.

Without sediment storage, climate change would be even more dramatic

Based on the analysis of archived data from several thousand soil profiles distributed over different regions of the world, the researchers were able to develop a model that shows that over the last 8,000 years around 80 billion tons of carbon were stored in sediments and thus withdrawn from the atmosphere. The amount corresponds to around ten percent of the total carbon content in the atmosphere or around 40 percent of all carbon emissions resulting from the conversion of grassland or forest into arable land. "This carbon dioxide-binding function is therefore an essential factor, without which the current problem of increasing greenhouse gas emissions would be even more dramatic," says co-author Dr. Sebastian Dötterl from the University of Augsburg. As a result of the introduction of machine farming and other reforms in agriculture in the 19th century, the rate of erosion and with it the creation of carbon-rich sediments increased almost five-fold compared to previous ages.

The scientists emphasize that their work is by no means to be understood as a recommendation to increase erosion rates. Soil erosion is responsible for many negative consequences that endanger ecosystems and the food supply of the world population. In addition, the carbon stored in the sediments is not permanently fixed, so it can be released back into the atmosphere with a time delay. "In the current discussion about rising temperatures and the consequences of climate change, however, our work makes a significant contribution to a better understanding and long-term modeling of greenhouse gas emissions," emphasize the scientists.

Publication: Human-induced erosion has offset one-third of carbon emissions from land cover change, Nature Climate Change

Contact:

Privatdozent Dr. Thomas Hoffmann
Institute for Geography
University of Bonn
Tel. 0261/13065592
Email: [email protected]

Dr. Sebastian Dötterl
Institute for Geography
University of Augsburg
Tel. 0821/5982776
Email: [email protected]


Additional Information:

http://dx.doi.org/10.1038/nclimate3263 Publication on the Internet


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