Grounds for Climate Change Mitigation in South Korea’s Tidal Mudflats

By Gebby Keny, Rice University §

Blue Carbon

Muddy boots on the shore of Wah Ohn beach. Photo by author.

“The trick is to step with your right foot before your left foot touches the ground.” Offered with a knowing smile and scalding-hot bowl of blended mudskipper soup, this seasoned mudflat fisherman’s advice would prove vital as my fellow tidal mudflat ecology researchers and I ventured out from the shore’s predictably stable ground and into a terrain I had only just learned to pronounce: getbol. Extending miles out into the Yellow Sea, though appearing only twice daily in rhythm with the moon’s orbital trajectory around the Earth and the Earth’s around the sun, getbol are Korean intertidal mudflat zones. “Get” refers to a coastal area, and “bol” a wide-open or plain field. Despite constant interaction with seawater, air, and inland rivers, getbol and the surrounding material-forces which constitute them are not formally governed by the Ministry of Ocean and Fisheries of Korea as a coherent ecological unit (Koh, Khim 2014). Thus, when getbol are discussed in Korean environmental policy, the unit of concern is strictly limited to the semi-aqueous area of land situated between the annual mean low tide line and shore. This walkable ground, frequently inhabited by fishermen, beachgoers, and countless other organisms delineates the stakes of most conservation efforts involving getbol. Notably, such conservation efforts have primarily focused on sustaining the maximum possible surface area of getbol. This is due to the fact that large-scale land reclamation efforts, which seek to increase the nation’s terrestrial territory horizontally out into the Yellow Sea, have historically presented the greatest threat to Korean getbol. Indeed, since 1980, over 1000 square kilometers of tidal mudflat habitat have been lost due to land reclamation alone (Koh, Khim 2014).

Mudflats off Ganghwa Island at low tide. Photo by author.

In an era of anthropogenic climate change, however, where sea-level rise, energy insecurity, and a wide array of other concerns threaten the longevity of life within (and well-beyond) intertidal zones, the literal and metaphorical ground of tidal mudflat conservation is shifting. This shift is perhaps best expressed by recent state efforts to understand and govern the distribution of carbon sequestered within South Korea’s tidal mudflats via the sedimentation of biomass and photosynthesis. This sequestered carbon is referred to as blue carbon and, because it is temporarily trapped in tidal sediment and unable to enter the atmosphere via oxidation, Korean scientists and policymakers are interested in leveraging this naturally-occurring phenomenon as a source of potential carbon offset. The possibility of such logic is, in part, a response to a 1997 provision made at the United Nations Convention on Climate Change to include biological carbon sinks as a form of carbon offset for national carbon emission totals. This shift in global climate policy marshaled a reconceptualization of forests, oceans, and soils as potential variables within national carbon emission calculations. Scientists from the Intergovernmental Panel on Climate Change estimate that over half of anthropogenic carbon emissions released since the Industrial Revolution have been “naturally” sequestered within biological carbon sinks via the global carbon cycle. Crucially, this statistic is dropping precipitously due to increases in anthropogenic perturbation of the biosphere—evinced by wide-scale land reclamation practices in South Korea. Calculating the rate of such emission offset losses and the sequestration capacities of coastal zones more broadly, however, remains a highly contested and politically-fraught undertaking due to scientific uncertainties and variable material contexts. Investigating such messy phenomena empirically in South Korea’s globally-distinct getbol was precisely what my fellow mudflat ecology researchers and I had set out to do that hot summer day. As I would quickly discover, however, doing so would make it increasingly difficult to keep one’s footing.


Carbon Footprints

A blue carbon scientist “walks” through tidal mud in the Anpoong Wetlands. Photo by author.

Blue carbon scientists collect sedimentation rate data in a mudflat near Wah Ohn beach, video by author

A blue carbon scientist collects sediment samples and temperature data in a mudflat near Wah Ohn beach, video by author

For those accustomed to walking upright along sidewalks or traveling in cars over asphalt, the idea that the ground is a solid surface containing various resources such as oil, minerals, or water is well taken. Indeed, one could argue that it is precisely our experience of the ground as a solid surface that allows us to conceive its capacity for containment in the first place. Unlike walking atop busy sidewalks in Seoul, however, walking in tidal mud is risky business. Surfaces leak and ooze. Unlike concrete, mud clings and sucks as it gives way. I step, I sink. Off balance, closer now to earth, I am reminded that legs are not lifted with will alone. Suction stalls sinking. The perpendicular tug of walls, forged by ties between skin and sediment, keep me from sinking all the way through—to what? Wresting skin from sediment, walls give—KER-FLURWP—a flood of cold, damp air lifts hairs off my calf and neck. Sinking, I lift one knee upward while scanning downward, seeking my—no, any—next step. Meanwhile, throughout all of this, I leave one-foot-deep (sometimes four-feet-deep) tracks in my wake. These holes, along with the thick layer of mud that has clung to my legs and abandoned its “natural” location in time and space, trouble the notion that what is contained beneath the ground here stays in place for very long.

In a recent essay titled “Ground,” Tim Ingold argues the state must be rendered calculable throughout time and space if it is to function as a foundation upon which a bounded territorial body and all of the human bodies living within it can stand (Ingold 2019). “Standing” in this context can signal all sorts of things, but for Ingold, it names a unique capacity to rationally delineate the when and where of a territorial body via its material composition. Put another way, it is only after ground has been fully accounted for that those standing upon it or, more precisely, those who wish to commit transgressions upon it, can be held accountable. In the context of blue carbon, accountability entails economic reward, as the ability to map and quantify carbon stored within tidal sediment offers a means of converting a naturally-occurring process into an economic resource owned by the state. By walking through tidal mud and collecting the amount of data necessary to prove its carbon contents, my colleagues and I helped stabilize an otherwise unwieldy ground into something upon which moral action and economic compensation could transpire. As I would learn back at the lab, mapping this newly minted economic resource temporally is an equally important aspect of such accounting efforts.


(Ac)countable Mud

In the context of South Korea, where speculative state funding is encouraging mudflat science researchers to develop methods for calculating blue carbon sums across vast coastal areas, core sampling is currently understood to be the most practical and scalable technique. This method requires three people to perform and involves driving a plastic tube vertically one-meter-deep beneath a mudflat surface. Once the tube is properly filled with mud, it is vacuum-sealed and taken to a freezer back at the lab. After the tube is frozen, mud samples are removed and cut into 5 cm long cylinders, producing 20 cross-section samples in total. Samples are then baked to remove all water contents, soaked in hydrochloric acid to remove all inorganic carbon like shells, and, finally, placed in a machine called an elemental analyzer. This machine vaporizes the remaining material and sends it through what is called a thermal conductivity detector, which produces an electrical signal proportional to the concentration of carbon present within a gas. Not only can each carbon concentration value within a given cross-section sample be aggregated with those of other cross-section samples to quantify an original core sample’s total carbon concentration amount, but each cross-section can be mapped temporally as well.

Scientific instruments are organized at the edge of Jeung Island. Photo by author.

Samples further towards the bottom of the core are understood to be older, whereas those near the top have been formed more recently. To quantify the time between cross-section samples, the general sedimentation rate of the mudflat from which the core sample was drawn must be calculated. This information is acquired via a somewhat less-sophisticated method than the elemental analyzer, by using a wooden stick, two hammers, and a sharpie marker. When I joined my interlocutors on monthly visits to their respective mudflat field sites, one of our tasks was to locate a 3-foot-long stick, which they had hammered into the mud months prior, and trace a thin sharpie line along the mud’s surface. Much like marks on a door frame that document the increasing height of children within a household, these sticks, once removed from the mud, chart a given area of mudflat’s vertical growth (i.e. its rate of sedimentation) through time. Once this sedimentation rate value is understood, the amount of time it took for each 5cm cross-section to form and ultimately store the amount of carbon confirmed by the elemental analyzer results can also be extrapolated. This then allows scientists to quantify how much blue carbon a given volume of mudflat likely sequestered within a given year, which ultimately allows environmental policymakers to say things like “for every year we preserve a given volume of mudflat space, we receive X amount of blue carbon in return.” This total can then, the logic goes, be subtracted from domestic carbon emission totals or traded within international carbon markets.



Footprints left in tidal mud by the author near Hwah Island. Photo by author.

Despite the development of techniques like core sampling to quantify blue carbon, efforts to calculate carbon stored within South Korea’s mudflats have faced considerable scientific uncertainty due in large part to both the dynamic material processes which animate this unique carbon sink and the habits of organisms living within it. Most notably, it is the way tidal forces and the movements of organisms living within tidal sediment mutually constitute and variably alter the material substance of tidal mud that trouble blue carbon science certainty. As was explained to me by one of my colleagues, South Korea’s tidal mud is a lot more like oatmeal than cereal. Because cereal is composed of large particles, its structural integrity is more easily compromised after it is penetrated. With oatmeal, however, a hole that is dug will likely sustain its form for some time. This is due to the size of oatmeal’s constitutive particles and the amount of water and or milk one might have added. In tidal mud, a Goldilocks threshold of varying dampness coupled with a vast distribution of small sediment particles from ocean-feeding rivers creates a similar phenomenon. Indeed, it is precisely this oatmeal effect that tidal sediment is so effective at sequestering carbon. An additional consequence of this, however, is that when benthic macro-organisms such as crab and bivalve burrow holes into tidal sediment, the structure of these holes is sustained for a considerable amount of time. This is referred to as bioturbation and is a variable of significant concern for scientists studying blue carbon.

When macro-organisms burrow in tidal sediment, a fundamentally anaerobic environment is temporarily made aerobic due to the penetrating column of air made possible by the open tunnel left in the organism’s meandering path. Due to this temporary shift in environmental conditions, bacteria that would otherwise not be able to exist in this area are able to feed on microparticles of organic matter and, crucially, produce carbon dioxide, which then freely floats into the atmosphere. Accounting for the amount of carbon dioxide released through such processes is something my scientist colleagues are struggling to account for in their blue carbon calculations. Additionally, as these creatures push, drag, and consume sediment on their winding journeys through tidal mud, they disrupt the material basis of core sample temporality. In the process, they also trouble the very ground of the state itself, confusing lines are drawn between nature, culture, and who gets credit for allowing life to unfold in specific ways, in particular parts of the world. In a way, such journeys exist outside time and space, as do the journeys of blue carbon scientists whose large boots leave one-to-four-foot-deep footprints in their wake. Nevertheless, despite existing outside the purview of blue carbon science, these footsteps are essential to its production. In my research, I’m trying to understand how this is the case and, more broadly, how such practices animate an unremarkable material—mud—with qualities integral to the preservation of state sovereignty and the world as we know it. This is where I’m currently stuck. But, lucky for me, nothing in tidal mud stays fixed for very long…

Jindongri tidal mudflat at high tide. Photo by author.


I would like to thank my friends and mentors at Seoul National University’s Benthos Lab as well as Young Rae Choi from Florida International University for her mentorship and supportThe ideas in this piece also took shape from the comments and encouragement of my fellow panelists at the annual meeting of the AAA in San Jose in November 2018.

Works Cited

Ingold, Tim. 2019. “Ground.” Volumetric Sovereignty Part 1: Cartography vs. Volumes. Frank Billé, ed. Society and Space ( Accessed 9/4/2019.

Koh, Chul-Hwan, Khim, Jong Seong. 2014. “The Korean Tidal Flat of the Yellow Sea: Physical Setting, Ecosystem and Management.” Ocean and Coastal Management 102:398-414.

Video Links: Video 1, Video 2

Gebhard Keny is a rising third-year PhD student in Rice University’s Anthropology Department. His dissertation research is situated in South Korea where he investigates how emergent climate change mitigation strategies and ongoing military practices animate the physical and conceptual terrain of the country’s western coastline. He is principally interested in how such processes align on intertidal mudflats, causing intertidal mudflats to become scientifically and existentially intelligible in new ways

This post is part of our thematic series: Ecological Times.