News

By Marcy Rockman, Lifting Rocks Climate and Heritage Consulting, for the SHA Climate Heritage Initiative

New legislation! Which at first glance doesn’t look like heritage legislation but has several historic preservation provisions (hat tip to Preservation Action for noting this). It also doesn’t say it’s climate action but if enacted, it could be. 

Bill is the Revitalizing Downtowns and Main Streets Act (H.R. 9002, S. 4963) and it would create a new 20% tax incentive to convert older commercial properties and office space into affordable housing. This approach is modeled on the US Federal Historic Preservation Tax Credit program (and this is where I jump up and down and note that action taken to support heritage often can have wider applications and benefits. See also: 1906 Antiquities Act). There are several provisions in the bill that  support and link to preservation of historic buildings. 

On the climate side, climate and carbon aren’t mentioned in these bills. But if you scoot over to the Carbon Avoided Retrofit Estimator (CARE Tool), it’s possible to do some estimations of the carbon that is held (embodied) in the buildings that are to be reused and the carbon emissions that are avoided through doing so. This combination of valuing and reusing existing and historic buildings is brought together in the graceful words of architect Carl Elefante, “the greenest building is the one that is already built.”

Featured Link: https://www.congress.gov/118/bills/hr9002/BILLS-118hr9002ih.pdf

For a listing of all blog posts in this series, visit our Climate Heritage Initiative page.

Photo credit: Screenshot of H.R. 9002 taken on August 29, 2024

By Marcy Rockman, Lifting Rocks Climate and Heritage Consulting, for the SHA Climate Heritage Initiative

Perspective on historic buildings today. This op-Ed from NY state speaks up about adaptive reuse of older buildings, with particular attention to how this allows for maintenance of local architectural character and history. I’m not remotely arguing against this, but this point reminds me that we seldom talk about why we see and understand older buildings to have character and newer buildings (generally speaking) to have less, how this reflects current allocation of planning power and financial control, and the challenges of developing new alternate paths. For example, development of new approaches for mass production of modular housing is an effort to address real issues in housing shortages (NYT, will add gift link close to time of posting: https://www.nytimes.com/2023/12/18/opinion/editorials/housing-costs-modular-homes.html), but which may further erode use of local and historical architectural styles and their connections to local environments and climates  without careful attention to these factors.

Featured Link: https://www.goerie.com/story/opinion/columns/2024/07/28/reusing-historic-buildings-economic-preserve-culture-identity-erie-brennan/74441370007/

For a listing of all blog posts in this series, visit our Climate Heritage Initiative page.

Photo credit: Architectural rendering of planned adaptive reuse of the 1890-1940 Erie Malleable Iron facility, captured from Brennan, D., Demolition or reuse of historic buildings? It’s a question of community values. GoErie (2024). https://www.goerie.com/story/opinion/columns/2024/07/28/reusing-historic-buildings-economic-preserve-culture-identity-erie-brennan/74441370007/

By Marcy Rockman, Lifting Rocks Climate and Heritage Consulting, for the SHA Climate Heritage Initiative

Two cultural connections here to the growing risks and impacts of wildfire. First, sharing the announcement from the Southeast Climate Adaptation Science Center that they will be hosting a virtual workshop on September 26, 2024, about Tribal approaches to managing fire in a changing climate (registration link here).

Second is a look at how archaeology can complement current efforts to realign policy and practice regarding wildfire. In this 2021 paper, Roos and co-authors bring together fire scar data, sediment and pollen records, and other evidence of landscape management of the ancient wildland-urban interface (WUI) on the Jemez Plateau from ca. 1100s to 1600s CE. What this combination allows is an evidence-based estimation of what it may have looked, felt, and smelled like to live for generations in proximity to sufficient regular controlled burning to keep larger fires at bay. It also provides a basis for envisioning forms of cultural adaptation that could support developing relationships with fire into the future.

Featured Link: https://www.pnas.org/doi/pdf/10.1073/pnas.2018733118

For a listing of all blog posts in this series, visit our Climate Heritage Initiative page.

Photo credit: Prescribed fire under ponderosa pine, New Mexico, photo by the U.S. Geological Survey and posted by the National Park Service at https://www.nps.gov/articles/000/wildfire-and-archeology-in-the-jemez-mountains.htm

By Marcy Rockman, Lifting Rocks Climate and Heritage Consulting, for the SHA Climate Heritage Initiative

More here on the Intergovernmental Panel on Climate Change (IPCC) with attention to equity and potential impacts on representation of cultural heritage in IPCC reports. 

The 2015 Paris Agreement calls on its party countries to periodically assess progress they are making toward its goals (reducing greenhouse gas emissions to limit global warming to under 2℃), a process known as the Global Stocktake. The first was held last year, 2023, and under the Paris Agreement they are to be held every 5 years after that, placing the next one in 2028. In turn, the IPCC prepares its major reports on a seven year cycle. Its most recent one, the 6th Assessment Report, also was released last year (2023). Keeping to this cycle, the 7th Assessment Report would be published in 2030. However, with the next Stocktake set for 2028 and wide recognition of 2030 as a target year for reducing emissions, there has been a call for the IPCC to accelerate its schedule and complete its next assessment report by 2028. 

Here’s the problem: IPCC assessment reports are massive undertakings, drawing volunteer labor from hundreds of scientists around the world. Scientists in the Global South, who tend to have less institutional support than those in the North, are pushing back, noting that an accelerated schedule would increase the stresses on their contributions.

For heritage, this 2022 analysis of the global distribution of climate-heritage research shows that while research on connections of climate change and heritage remains sparse worldwide, it is particularly lacking in attention to the countries and heritage of the Global South. This raises concerns (mine, at least), that – if not otherwise addressed – an accelerated IPCC timeframe would further limit capacity of scholars in the Global South to gather, share, and incorporate new research on climate-heritage from across that region. 

Featured Link: https://www.climatechangenews.com/2024/08/05/ipccs-input-into-key-un-climate-review-at-risk-as-countries-clash-over-timeline/?utm_source=cbnewsletter&utm_medium=email&utm_term=2024-08-06&utm_campaign=Daily+Briefing+06+08+2024

For a listing of all blog posts in this series, visit our Climate Heritage Initiative page.

Photo credit: Global distribution of UNESCO World Heritage Sites per country, Fig. 1b from Simpson, N.P., Clarke, J., Orr, S.A. et al. Decolonizing climate change–heritage  research. Nat. Clim. Chang. 12, 210–213 (2022). https://doi.org/10.1038/s41558-022-01279-8

By Marcy Rockman, Lifting Rocks Climate and Heritage Consulting, for the SHA Climate Heritage Initiative

The Intergovernmental Panel on Climate Change (IPCC) is now taking nominations for authors for its upcoming special report on Climate Change and Cities (SR Cities). Nominations are made through national IPCC focal points; in the US, the IPCC focal point is the Dept. of State in collaboration with the US Global Change Research Program. US nominations, and self-nominations are welcome, can be made here: https://contribute.globalchange.gov/. More information and a list of all national focal points around the world are here. Deadline for nominations is September 16, 2024.

The outline for the SR Cities includes several touchpoints for archaeology and heritage. These include but are not limited to:

• Chapt. 1 Framing of multi-dimensional urban characteristics, including physical, socioeconomic and environmental features
• Chapt. 2 Understanding and learning from the past (global climate, hazards, crises, socioeconomic developments)
• Chapt. 3 Local risk assessments using scientific information, Indigenous Knowledge, and local knowledge of impacts, types and scales of adaptation responses
• Chapt. 4 Structural inequity, gender, colonialism, and justice

For inspiration, see the July 2024 special issue of Historical Archaeology, Urban Historical Archaeology of and as Dissonance—An Invitation for Collaboration. An example of archaeological concepts incorporated into broad issues of urban sustainability is here. New research on trends in adaptation in coastal cities around the world is here.

Featured Link: https://contribute.globalchange.gov

For a listing of all blog posts in this series, visit our Climate Heritage Initiative page.

Photo credit: Lower Manhattan, 1755, Fig. 1 from Aubey, M., Britt, K.M. & Gold, K. Policing, Power, and Protests: Landscapes of Surveillance in Private and Public Spaces in Lower Manhattan. Hist Arch (2024). https://doi.org/10.1007/s41636-024-00512-9

By Marcy Rockman, Lifting Rocks Climate and Heritage Consulting, for the SHA Climate Heritage Initiative

Welcome to Micro-Climate, the new small-size climate blog series from the Society for Historical Archaeology!

This blog series is part of the Society for Historical Archaeology’s (SHA) new Climate Heritage Initiative (CHI), which has the twin goals of growing capacity to work on and speak about climate change across the field of historical archaeology and building a new clear voice from SHA about archaeology, heritage, and climate change that will reach out widely. This small but mighty blog is taking on the challenge of doing both. 

Twice a week, climate archaeologist Marcy Rockman (and occasionally a guest writer) will share a piece of recent climate-related news with commentary from an archaeological, heritage, and/or cultural perspective in 300 words or less. 

With that, there’s no better place to start than this recent essay in The Conversation. In May and June of this year, there was a spate of articles about despair amongst climate scientists about the lack of sufficient progress in addressing climate change in the face of accelerating change and impacts. While this despair is not unwarranted, this article makes the key point that “…the concerns and practices of climate social scientists have not featured prominently in these discussions.” This is a significant oversight because 

“Climate natural scientists are not trained to understand why people aren’t listening to their entreaties or the obstacles to and opportunities for action. Climate social scientists, on the other hand…are experts in humanity’s efforts to address climate change.”

To be clear, I put archaeologists who work with processes of industrialization, colonization and globalization that have developed the modern world, and methods and practices of working with communities to engage with their histories, equity, and environmental justice in the column of climate social scientists.

As the essay notes, “The climate social science community starts their teaching and research where the bulk of the “climate scientists are despairing” type articles end their discussions.” Indeed. Archaeology in relation to climate change is a path for hope. This is where we begin. 

Featured Link: https://theconversation.com/heres-how-climate-social-scientists-are-finding-their-way-in-the-era-of-climate-crisis-229861?utm_source=cbnewsletter&utm_medium=email&utm_term=2024-06-10&utm_campaign=Daily+Briefing+04+06+2024

For a listing of all blog posts in this series, visit our Climate Heritage Initiative page.

Photo credit: Inspirational quote drawn from Hoffman, M., Here’s how climate social scientists are finding their way in the era of climate crisis, The Conversation (2024), shared at link above.

By Laura Seifert, Fort Pulaski National Monument, Savannah, Georgia

Work began on Fort Pulaski in 1829, but before one brick could be laid, a complex ditch and dike system was dug to engineer Cockspur Island from a marshy hammock into solid ground that could support the massive brick fort. In fact, it would be several years before the first bricks were laid due to the wide scope of the ditch and dike system. In addition, storms damaged the dikes and main ditch twice in the first few years forcing workers to rebuild some of the work. Despite subsequent small changes, including more storm repairs and the Civilian Conservation Corps’ (CCC) work that fixed damage due to neglect, Fort Pulaski’s ditch and dike system has remained largely intact and held the fort steady for nearly 200 years.

Image 1. 1843 map of Cockspur Island, showing Fort Pulaski and the surrounding ditch and dike system, which includes the wet moat around the fort and demilune. (Image courtesy of the National Archives <National Archives NextGen Catalog>)

Hurricanes and other storms are the refrain of Cockspur Island’s history. Situated near the mouth of the Savannah River, this low-lying, coastal Georgia island is very susceptible to storm damage. An 1804 hurricane largely removed an earthwork fort and wooden blockhouse from the landscape and killed half of those present. Another hurricane in 1854 lifted the Carpenter’s Shop off its foundation and swept away the building and its contents. Meanwhile, the fort’s caretakers huddled in the top floor of the only two-story building, having broken out the lower floor’s weatherboarding to allow storm surge to flow through rather than collapse the building. More recently, Hurricanes Matthew (2016) and Irma (2017) caused considerable damage. The island resembled a bathtub when storm surge water flooded over the dike then became trapped because broken culverts and clogged ditches could not let the water back out. Bridges to access the fort floated away, and historic wooden flooring in the casemates was displaced.

Image 2. Fort Pulaski National Monument consists of two islands: McQueens Island that is largely tidal marsh and the smaller Cockspur Island to the north, which holds Fort Pulaski itself. (Image courtesy NPS/Seifert)

Compounding these deferred maintenance problems with the drainage system, the fort faces new challenges due to human-caused climate change. Sea level rise and higher tides are obvious on the landscape and predicted to worsen. During king tides, water can be more than 10 feet over the MLLW (mean lower low water <NOAA Tides & Currents>). Rising groundwater and saltwater intrusion are the hidden threats. Park archeologists were horrified to find their units nearly full of water after a simple rain event in January 2023. This flooding severely delayed fieldwork to the extent that no fieldwork was conducted in February, and then excavation could only be conducted intermittently with breaks of several days or up to two weeks depending on the rainfall. Even when the units did not contain standing water, excavation was often conducted in very short bursts as archeologists would dig five to ten cm before encountering groundwater again. Repeated groundwater flooding sometimes caused the unit’s walls to erode. For two units, this damage, in addition to persistent groundwater, caused us to abandon and backfill the units before we reached subsoil.

Image 3. Archaeologist Sam Matera expresses our feeling about flooded units in late January 2023. (Image courtesy NPS/Seifert)

As sea level rises, saltwater inundation will be an increasingly destructive factor. Saltwater’s effect on terrestrial artifacts can be surmised through studying marine archeological sites. More, or perhaps all, the terrestrial artifacts excavated will need to undergo conservation or different cleaning techniques due to the artifacts’ exposure to salts and salt water. There are examples from England of white clay tobacco pipes spalling after excavation because they were not desalinated before permanent storage. “Pipes from marine or estuary conditions will have absorbed salts and these need to be removed by soaking the fragments in frequent changes of fresh water for a week or two before allowing them to dry out” (Higgins 2017:5). At our most recent excavation, all the iron artifacts were severely corroded, most beyond identification, from excess amounts of water, including saltwater and brackish water. Fort Pulaski archeologists are considering soil testing to determine salinity levels to guide future laboratory methods and conservation decisions. All of the above factors will lead to greatly increased costs for archeological projects.

Image 4. Cutlery handle from a kitchen at the Fort Pulaski’s Workers’ Village. While the carved bone is in excellent shape, the iron has rusted and oozed everywhere. Right: Iron hook from the same site. This artifact was by far the best-preserved iron object found. (Image courtesy NPS/Seifert)

As the island becomes more saturated, soils could become less stable–essentially, a wet sponge doesn’t hold as much weight as a dry one. Park staff have begun a project to monitor Fort Pulaski with crack monitors and tilt monitors to analyze the fort’s structural stability over the next decades. While stopping sea level rise is above my pay grade, we are working on ways to adapt and keep the sponge (Cockspur Island) dry, or at least drier. One project is repairing and raising the dike to keep the water out. A group of students from Georgia Institute of Technology studied this problem for their senior capstone project and worked with the US Army Corps of Engineers (USACE), Savannah District, to develop a concept plan for raising the dike. We are currently seeking funding for the final design and implementation.

Image 5. Projected sea level rise for Fort Pulaski National Monument in 2050. Note the flooded ditch and dike system; this model assumes no alterations or improvements to the drainage system. (Image  courtesy NPS/Seifert)

The complimentary project is to clean out the ditches, repair culverts, and replace tide gates to allow the island to drain, as well as being able to flush the system on a regular basis to promote a healthy wetland ecosystem. The first phase of this project took place in early 2024. It was ugly.

Image 6. After vegetation removal, wooden matting (right) was placed to support heavy equipment used to clean out Ditch 5, seen at left. This picture was taken after the ditch was cleaned out but before the area was reseeded. (Image courtesy NPS/Seifert)

Wooden matting was placed along the ditch, and heavy equipment was used to dig out accumulated sediment and vegetation. The culvert was repaired, and the flap gate allowing access to the Savannah River was replaced. Then the matting was removed, and the area reseeded. An archaeologist monitored the project, but few artifacts were found, which is not surprising considering the CCC picked the moat nearly clean. (Today, the park has approximately 1,000 accessioned artifacts from the CCC repairing the ditches and moat in the 1930s.)

This initial phase began with Ditch 5, which was the most severely damaged. There are still roughly 3.5 miles of ditches to repair, with varying levels of damage. For comparison, Ditch 5 is approximately one-third of a mile, which is less than 10% of the total length of the ditches. The final designs are finished, so once we receive more funding, we can complete more work. Our local USACE, the Savannah District, has been our preservation partner in engineering the work, creating plans, and contracting the project. They feel personally involved in this project. Fort Pulaski, as a US Army fort, is their legacy project, and the USACE staff is considered a descendant group.

Image 7. Completed Ditch 5. Picture taken in June 2024. (Image courtesy NPS/Seifert)

Ultimately, this project should help manage water and flooding on Cockspur Island while also rehabilitating and maintaining a historic element of the cultural landscape, one that is part of our enabling legislation. As we celebrate the national monument’s Centennial in October, we look forward to keeping the fort above water and accessible to the public for another 100 years.

Image 8. CCC workers excavating the fort’s moat in the 1930s. It’s not going well. (Image courtesy of the Fort Pulaski archives)

Sources

Higgins, David

2017    Guidelines for the Recovery and Processing of Clay Tobacco Pipes from Archaeological Projects. September 2017. National Pipe Archive, University of Liverpool. http://www.Pipearchive.co.uk/pdfs/howto/Guidelines%20Ver%201_2%20030917.pdf

By Charlotte Jarvis and Ole Varmer

Bottom Trawling 

Ecologists and fishery scientists have been concerned about bottom trawling for centuries. The first known reference to the activity is in a 1375 English Parliamentary document and that initial mention highlights the destructive nature of the practice (Petition by the Commons to King Edward III, 1376 seen in Bolster 2012, p. 235). Bottom trawling impacts the natural heritage of the ocean in many ways, including by reducing topography, compression, and resuspension of sediments, decreasing complexity, causing both physical and chemical damage to the ecosystem, and the collapse of fish stocks. But it is not just the natural heritage that is impacted by this activity. 

Although legislation that limits trawling can help biological communities rebound, the archaeological material lost can never be recovered (Brennan et al. 2015). Maritime archaeologists and marine ecologists need to communicate and work together with fishers and policy makers to find ways to limit harm. Damage to shipwrecks can include mixed sediments, changing chemical degradation processes, artefact damage and movement, and destruction of a site’s context. Additionally, nets and other fishing gear can snag on a wreck, warping the metal features or cutting through wooden elements. The site’s integrity can be completely destroyed. 

Deep Seabed Mining 

There are also future challenges facing UCH. Deep seabed mining operations (DSM) that interact with tangible UCH and intangible. Deep seabed mining (DSM) is a potential commercial industry attempting to mine mineral deposits from the seafloor, in the hopes of extracting commercially valuable minerals such as manganese, copper, cobalt, zinc, and rare earth metals. However, this mining is posed to destroy a thriving and interconnected ecosystem that hosts a staggering array of biodiversity: the deep ocean.

Commercial DSM has not started, but various companies are trying to make it a reality. Current proposed methods of nodule mining include the deployment of a mining vehicle, typically a very large machine resembling a three-story tall tractor, to the seafloor. Once on the seabed, the vehicle will vacuum the top four inches of the seabed, sending the sediment, rocks, crushed animals, and nodules up to a vessel waiting on the surface. On the ship, the minerals are sorted and the remaining wastewater slurry (a mix of sediment, water, and processing agents) is returned to the ocean via a discharge plume. 

Current International Seabed Authority (ISA) exploration and exploitation draft regulations are not sufficiently protective of UCH. For example, the regulations do not require the real time monitoring of operations and transmission of relevant data, which would enable identification of tangible UCH and the halting of destructive activities to protect that heritage. 

DSM will also affect intangible cultural heritage. In one specific example, noise from DSM has the potential to negatively impact local practices, such as shark calling, as well as the migration of whales– which have cultural importance to many people globally (Tilot et al. 2021). Concerns have also been raised about DSM’s interactions with some cultures’ understanding of responsibility to the ocean or special regard for the deep ocean. Such conversations have not found a place in regulatory development at the ISA but a new intersessional is meeting to work on this. 

Figure 1. Threats to UCH from seabed mining. A sample of the UCH at risk from the ISA’s proposed seabed mining activities (Source: Image created by Charlotte Jarvis based on ISA Information, SPREP Pacific Wreck Database and Turner et al. 2020).

Potentially Polluting Wrecks

Additional threats to heritage, both natural and cultural, can come from the material itself. While the wrecks from the World Wars are part of our cultural heritage, they are also posing a significant pollution threat to the marine environment, fishing, and other livelihoods that are dependent upon a healthy ocean. A potentially polluting wreck (PPW) is a shipwreck containing a cargo or a large volume of its own fuel that remains within the wreck and has the potential to cause an environmental hazard should the structure become compromised and either leak or catastrophically release (see Brennan et al. 2023 for more information). 

The wrecks identified as PPWs are most thought to be those sunk during World War II, particularly oil tankers, but also include freighters, and include ships from parts of the twentieth century that foundered in storms. Only in the aftermath of the Deepwater Horizon spill and the research conducted in the Gulf of Mexico since, do we have a better understanding of some of the environmental impacts of such disasters to the deep-sea ecosystem. While some oil leak origins are known, many come from mystery sources and will pose future damage (NOAA 2012). 

A New Project and Steps Forward

TOF has a new project that aims to bring awareness to these threats to UCH from bottom trawling, potentially polluting wrecks, and deep seabed mining. The project is in partnership with the Lloyd’s Register Foundation Heritage and Education Centre and has cooperation from The International Committee on Underwater Cultural Heritage (ICUCH) within the International Committee on Monuments and Sites (ICOMOS. It is an endorsed Activity under the UN Decade for Ocean Science. While the UN Decade for Ocean Science (2021-2030) has hundreds of endorsed ocean science activities, projects, and programmes that relate to natural heritage and ocean biosciences, there are very few endorsements that focus on cultural heritage. The Cultural Heritage Framework Programme, led by the Ocean Decade Heritage Network was the first and is to date, one of the only ones still. We are also very fortunate to have some of the Framework Programme team as well as the Heritage Network team writing contributions for the books and helping develop the themes. 

Cultural heritage and natural heritage are intertwined when it comes to the ocean. UCH can support ecological marine biodiversity and helps boost sea connectivity. For example, with fishing, Pearson, and Thompson (2023, 3) argue that it is beneficial for sites with high UCH and high natural heritage to co-occur and be used strategically together. Shipwrecks often function as artificial reefs providing habitats, shelter, and adding hard materials to an otherwise soft seafloor (Brennan 2016, 172; Krumholz and Brennan 2015). Through this process of ‘spill over,’ protected shipwrecks can help increase the strength of surrounding fish stocks. Shipwrecks can be as indispensable to the seafloor ecology as a natural coral reef or seamount. Thus, shipwrecks should not be viewed solely in a cultural significance context; they are part of the natural ocean landscape as well as our cultural history.

Sources

Bolster, W. Jeffrey. 2012. The Mortal Sea: Fishing the Atlantic in the Age of Sail. Cambridge, Mass. London: Belknap Press of Harvard Univ. Press. 

Brennan, Michael L., Dan Davis, Robert D. Ballard, Arthur C. Trembanis, J. Ian Vaughn, Jason S. Krumholz, James P. Delgado et al. 2015. “Quantification of Bottom Trawl Fishing Damage to Ancient Shipwreck Sites.” Marine Geology 371, no. 2: 82–8. https://doi.org/10.1016/j.margeo.2015.11.001.

Brennan, Michael L. 2016. “Quantifying Impacts of Trawling to Shipwrecks.” InSite Formation Processes of Submerged Shipwrecks, edited by Matthew E. Keith, 157–79. Gainesville: University Press of Florida.

Krumholz, Jason S., and Michael L. Brennan. 2015. “Fishing for Common Ground: Investigations of the Impact of Trawling on Ancient Shipwreck Sites Uncovers a Potential for Management Synergy.” Marine Policy 61, 127–33. 

National Atmospheric and Oceanic Administration. 2012. 2012 Risk Assessment for Potentially Polluting Wrecks in US Waters. https://sanctuaries.noaa.gov/protect/ppw/pdfs/2013_potentiallypollutingwrecks.pdf.

Pearson, Natali, and Benjamin S. Thompson. 2023. “Saving Two Fish with One Wreck: Maximizing Synergies in Marine Biodiversity Conservation and Underwater Cultural Heritage Protection.” Marine Policy 152, 105613. 

Tilot, Virginie, Klaas Willaert, Bleuenn Guilloux, Wenting Chen, Clement Y. Mulalap, François Gaulme, Tamatoa Bambridge et al. 2021. “Traditional Dimensions of Seabed Resource Management in the Context of Deep Sea Mining in the Pacific: Learning From the Socio-Ecological Interconnectivity Between Island Communities and the Ocean Realm.” Frontiers  in  Marine Science 8  (April):  637938. https://doi.org/10.3389/fmars.2021.637938.

Turner, Phillip, Sophie Cannon, Sarah DeLand, James Delgado, David Eltis, Patrick Halpin, Michael Kanu, et al. 2020. “Memorializing the Middle Passage on the Atlantic Seabed in Areas Beyond National Jurisdiction.” Marine Policy 122. https://doi.org/10.1016/j.marpol.2020.104254.

By Steven J. Filoromo, RPA, TerraXplorations, Inc., Baton Rouge, Louisiana

Bayous are subject to constant change over the long course of history. The rate of change today is unprecedented. As a result, many archaeologists working in southern Louisiana are developing unique approaches to understand the changing environments and their heritage at risk.

Mentions of Louisiana’s swamps and bayous conjure images of a shifting landscape of wild or bucolic imagery. These images often include scenery where Spanish moss hangs over still water while cypress knees chart clear paths for flat boats to cross. One could imagine the diversity of bird calls filling the air while a sea of lush green forests directs one’s path through a seemingly thick and remote wood.

Set back from the Mississippi River’s modern levee system, agricultural fields become a sea of sugarcane set ahead of a thick backdrop of swamps and bayous. Nevertheless, this seemingly remote landscape is a significant cultural resource. While difficult to navigate now, these waterways provided the same pathways where enslaved individuals formed networks towards freedom during times of antebellum oppression, and others including, but not limited to: Isleños, Acadians, and the ancestors to modern Chitimacha, Coushatta, and Houma (to name a few) who used these waterways to transport items and ideas. Archaeologically speaking, probability modeling relies upon data that, not to the researcher’s fault, may not consider historical environments, land use, and other environmental data that may not necessarily appear within historic cartographic sources. The core issue with researching settlements in these environments is that archaeologists could assume relative stability over time. The course of the bayou is not static. In the face of a changing climate suffering from significant losses to land and heritage, we are left with opportunities to develop creative ways to identify this heritage at risk. One such methodology we can employ is shallow geophysical surveying.

Figure 1. Sugarhouse ruins in the backswamp, Ascension Parish. Photograph by Steven Filoromo, July 2022.

Within southern Louisiana, my colleagues and I are fortunate to have had opportunities to employ magnetometry across various sites. Magnetometry is a unique form of shallow geophysical surveying. The data in total across a site or landscape create a palimpsest of natural and cultural features, condensing approximately two meters of stratigraphy within an atemporal two-dimensional image. Things like relict streams, landscape modifications, hearths, architecture, and more can appear. While those distinct cultural features are generally the target of archaeological research, locations of relict landforms such as ancient bayous or relict streams (coulees in Acadiana) are also critical to understanding changes in the landscape. The appearance of these features within magnetic data depends on mixed variables. In a basic sense, the magnetic gradient of sediment layers ranges depending on their residual (remanent) magnetization from the acquisition from an external field and their ability to be magnetized from an applied field (magnetic susceptibility). These differences in the gradient are significant as relict channels have different remanent magnetization, thus appearing in contrast to the surrounding environmental and cultural features (e.g., Stele et al. 2020; Heller & Evans 2002).

During recent archaeological projects in Iberville Parish, where we were determining the integrity of a sugarhouse site (Phase II testing) and a full-scale excavation of a large Coles Creek village (Phase III data recovery), we conducted a magnetometry survey before any new ground disturbance. We covered approximately 3.3 acres for the sugarhouse, and at the Coles Creek period village, we surveyed 7.33 acres. Fortunately, both sites sit within a similar location set back from the levee, along with the exact change in elevation within the adjacent sugarcane fields. For the sugarhouse, there were very few indications of any distinct cultural features; whereas, at the village, there were numerous anomalies related to structures, a historic road, and several ditches. Notable between both datasets were subtle contrasts in low magnitude (between 2 and -2 nT, or nanoTeslas) magnetic variations across both areas. The general trend between both locations was that an area of low magnitude negative magnetic variation defined the boundary between the fields and bayous. The difference between the two locations was that the interior of the former bayou at the village contained more prominent, subtle anomalies with positive magnetic variation.