Searching for stratigraphic signatures to define the start of the Anthropocene in Korea

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Searching for stratigraphic signatures to define the start of the Anthropocene in Korea

Myung Ae Choi

In September 2019, a group of natural and social scientists from the Center for Anthropocene Studies (CAS) gathered at Bongpo Wetland, Goseong-gun, Gangwon-do. Two sets of boring devices were soon placed to extract wetland sediments as deep as 8.5 meters under the ground. This field data collection was one of the first research activities in the country to collect and identify stratigraphic signatures of the Anthropocene in Korea.

The recent diagnosis of the Anthropocene claims that humankind has emerged as an earth-changing force. An immediate follow-up question would be when the Anthropocene started. Four proposals have been made to separate the Anthropocene from the Holocene: 1) The spread of agriculture and deforestation in the Neolithic Period; 2) The Columbian Exchange between Old World (Europe) and New World in the 17^th century; 3) the Industrial Revolution at around the 19^th century; 4) the mid-20^th century. While scholars support different proposals for diverse and convincing reasons, the international community of relevant geologists, the International Commission on Stratigraphy (ICS), favours the mid-20^th century hypothesis that the rapid population growth, urbanisation, and industrialization, what is called as “the Great Acceleration”, has become responsible for the unprecedented changes in earth systems.

Then, what would be the geological evidence of the Anthropocene in the Earth’s geological history? With a view of formalising the Anthropocene as a new and additional geological epoch, the ICS has been searching for stratigraphic signatures of the Anthropocene in sediments and ice. They are looking for:

• New anthropogenic materials: aluminum, plastics, concrete
• Radiogenic signatures and radionuclides: excess Carbon-14, Plutonium-239
• Changed geochemical signatures: elevated concentrations of polyaromatic hydrocarbons, polychlorinated biphenyls, pesticide residues
• Carbon cycle evidences: increased concentrations of atmospheric CO² and CH⁴

(source: Waters et al (2016) “The Anthropocene is functionally and stratigraphically distinct from the Holocene”, Science, vol 351, no.6269)

Korean geologists affiliated with CAS have recently started to search for stratigraphic markers of the Anthropocene in Korean estuaries and wetlands. Prof. Guan-Hong Lee, Inha University, and his research team have collected estuarine sediments from four major rivers – Han, Geum, Yeongsan, and Nakdong. They are tracing new anthropogenic materials – such as microplastics, black carbon – and geochemical markers, while examining lithological characteristics that are distinctive from that of the Holocene. Korean estuaries would provide useful data to define the beginning of Anthropocene specific to the Korean context, as they are very close to urban and industrial complexes, and also heavily altered. Dr. Wook-Hyun Nahm, Korea Institute of Geoscience and Mineral Resources, has worked on the timing when the anthropogenic signals of global warming overwhelmed the natural signals of climate fluctuation in Korea during the past 2000 years. While collecting and analysing geological records, the team also collects historical cases of human activities, such as cultivation, logging, and reclamation, which could explain the artificial sediments in the strata.

At Bongpo, Prof. Lee’s team collected recent wetland sediments as deep as 1.5 meters under the ground. Alongside other estuarian sediments collected from major rivers of Geum, Yongsan, and Nakdong, these samples are brought into his lab for geological analysis. Dr. Nahm’s team went into deeper by digging down to 8.5 meters, which would allow the team to look at geological records of the past 10,000 years. Dr. Myung Ae Choi, a human geographer at CAS, joined these geologists at Bongpo to collect the stories of how local residents have used the wetland for the past decades. These researchers work together by putting the geological data in conversation with the written and verbal accounts of human intervention in the recent past. Such interdisciplinary work, although at its early stage, could shed some light on the important question when the Anthropocene started in Korea.