Agriculture

Deforestation, agriculture triggered soil erosion 4,000 years ago: Study

Increased sediment deposits and changes in land use showed the degradation of soil during the last four millenia

 
By DTE Staff
Last Updated: Wednesday 30 October 2019
Photo: Getty Images

Human activities such as agriculture and deforestation intensified global soil erosion 4,000 years ago, according to a study.

While weathering of soil and erosion have, since millennia, known to be controlled by changing climatic patterns and tectonic impacts of the planet, the new study suggests a role of human practices and land use-change.

Soil erosion has a direct impacts on climate and society, as it decreases the productivity of ecosystems and changes nutrient cycles

For the study, a team of researchers from the Max Planck Institute, a Germany-based non-profit, used radiocarbon dating techniques recorded temporal changes of soil erosion by analysing sediment deposits in more than 600 lakes worldwide.

Of these, 35 per cent showed an increasing sediment accumulation approximately 4,000 years ago, said Nuno Carvalhais, group leader at Max Planck Institute for Biogeochemistry.

To understand the cause they analysed pollen fossil records and observed a decline in the tree cover. 

The decrease indicated “land-cover changes, in particular land clearances, eg, for agriculture and settlement, that, in turn, are likely to lead to soil degradation and erosion,” said French geoscientist Jean-Philippe Jenny from the varsity.

Changes in land cover was identified as the main driver of soil erosion in 70 per cent of all studied watersheds. This suggests that human practices intensified soil erosion much before the advent of industrialisation.

Socio-economic developments during human settlements also correlated with sediment accumulation in lakes, a proxy for soil erosion. 

For example: Soil erosion was delayed in North America than in Europe. It was because agricultural practices was introduced to North America, only after colonisation.

“On the contrary, the decrease of soil erosion in 23 per cent of sites is likely associated with increased water use and river management practices, especially in the Roman and Chinese empires 3,000 years ago,” showed the study.

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