News

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.

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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.

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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)

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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.

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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.

By Alicia Johnson, Graduate Researcher, Alexandria Centre For Maritime Archaeology & Underwater Cultural Heritage

While scouring the depths of the Red Sea in 1955, Jacques Cousteau, a famed explorer, discovered the famous Thistlegorm, a British merchant vessel submerged off the Southern tip of the Sinai. The extensive documentation and international media coverage of Cousteau’s discovery spurred significant public interest in maritime exploration and launched the shipwreck’s reputation as a remarkable dive site. It is estimated that Thistlegorm, a World War Two British warship sunk by Luftwaffe forces in 1941, brings in 5 million Euros of revenue a year and attracts thousands of visitors each year to the Red Sea of Egypt. Over time, as diving gained popularity, the wreck has become a large attraction for international divers and was recently awarded the #2 Best Shipwreck dive by PADI this year. 

Thistlegorm photogrammetric model by Simon Brown.

Throughout history, ships have been anthropomorphized and evolved alongside mankind, often taking on a life of their own; even in death, a ship’s demise is as dramatic as that of its flesh and bone crew. Akin to its makers, a ship’s death can be followed by its resurrection via explorers, filmmakers, musicians, story tellers, divers, maritime archaeologists, and museums. In short, a ship’s life does not cease just because it slips beneath the seas; instead, a shipwreck metamorphosizes into a valuable time capsule and an irreplaceable addition to humanity’s shared maritime cultural heritage. These historic shipwrecks can provide information benefitting academic research, stories, myths, and media which delight the public, sights of attraction for tourism and sports divers, and avenues of commerce, revenue, and employment which stimulate the local economy.

Protection of Historical Shipwrecks

Prior to the advent of recreational SCUBA diving, wrecks remained largely inaccessible to people and preserved by the anoxic underwater environment; however, with the popularity of recreational diving, shipwrecks have become SCUBA tourism destinations. Whereas deep sea wrecks remain largely unreachable by recreational SCUBA divers, shallow water wrecks have become an attraction for divers, a target for looters and salvers, and are at risk of decomposition and destruction.

Classified as Underwater Cultural Heritage (UCH) by UNESCO’s 2001 Convention on the Protection of the Underwater Cultural Heritage, historic shipwrecks (<100 years of age) are acknowledged to be “an integral part of the cultural heritage of humanity and a particularly important element in the history of peoples, nations, and their relations with each other concerning their common heritage.” As protection is afforded to shipwrecks older than 100 years, WWII ships, such as Thistlegorm, are excluded from protective legislative, leaving them in a purgatorial status of increased degradation.

Popular historic Wreck Dives of the World

Many diving destinations are found in developing countries which offer travelers a pleasing and budget friendly vacation. For example, several premiere wreck dives, such as Thistlegorm (Egypt), Basuanga Bay (Philippines), and Liberty (Indonesia) are historic sites which attract many visitors a year and stimulate the local economy. The positive influx of tourism benefits the local community and provides employment opportunities to the local population.  Dive tourism creates a need for hotels, marinas, boats, dive centers, restaurants, retail and so forth.  During the last half century, the Blue Economy has prospered and brings high value tourists to developing countries.

However, many of these historic shipwreck sites, such as the Thistlegorm in Egypt, are at-risk heritage sites and face difficulties with archaeological efforts to excavate, document, and manage the site. Effective heritage management can be hampered by domestic political issues, insufficient resources, limited funding, and a shortage of local specialists; mismanagement, or lack thereof, can lead to a lack of oversight, loss of archaeological integrity, unsustainable number of visitors, and little public outreach—all of which can be harmful to a site’s preservation and diminish cultural appreciation. Without effective management these sites deteriorate at a faster pace and face the risk of being irreparably damaged or lost.  

History of the Thistlegorm

While the Thistlegorm site has become a flagship of Scuba and Egyptian tourism, the wreck is, more importantly, a grave and a reminder of the sacrifices made during WWII’s North African theater. Lost during WWII, Thistlegorm was an armed commercial freighter ship carrying a cargo of vehicles, aircraft spares, and ammunition, and sunk by a Nazi Luftwaffe air raid in 1941. Operating with a crew of 42, the 131m Thistlegorm was an Albyn Line merchant refitted with 4in high angle anti-aircraft gun, 12pdr low angle gun for surface targets, and machine guns.

Thistlegorm faces unavoidable threats such as weather and currents; however, our human impact on the site is manageable. Ongoing Maritime Archaeological Projects, such as the Wrecks at Risk and Project Thistlegorm, are working to document the site and have created a photogrammetric model of the wreck, similar to the recent Titanic scans. Simon Brown has also created an orthomosaic of the wreck. In the future, efforts are being made to create a more efficient mooring system and to have the site recognized as a UNESCO Cultural Heritage Site; but thus far, the shipwreck is open year-round to copious numbers of divers and a destination offered by many dive companies from the Sinai and Hurghada.

If you can visit Egypt…and want to dive Thistlegorm…

be sure to book a live aboard safari out of Sharm el Sheikh or Hurghada. Egypt has some of the world’s most beautiful and affordable diving and consistently ranks as one of PADI’s top countries to dive. Enhanced by historical shipwrecks, such as Thistlegorm and Carnatic, the Red Sea is characterized by the colorful aquarium like reefs teeming with sea goldies. Diving the Red Sea grants visitors an immersive and interactive experience with marine biodiversity and a chance to explore the rich history of the Indo-European trade and military history.  A visit to the underwater museum of Thistlegorm will be unlike any other trip you have ever had, and you’ll swim away with travel photographs to last a lifetime. If you would like to know more about the Thistlegorm, please check out the book: Diving the Thistlegorm: The Ultimate Guide to a World War II Shipwreck.

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By Allyson Ropp, Ph.D. Candidate, East Carolina University

Think back to your favorite story. What made it so exciting? Was it the characters? Was it the conflict or problem that the main characters needed to solve? Or was it how the characters ended up solving the problem? Maybe it was all three!

What all good stories have in common is a beginning, a middle, and an end – each setting up an important part of the story that brings you into the action. The beginning is the setup. It provides the exposition of the story, introducing us to the main characters and their world. The middle presents a problem, conflict, or situation the characters must address. This could be a wrecked ship on a voyage home or the loss of a parent, but regardless of what it is, it provides a problem for the characters. The end wraps up the story and allows the characters to solve or achieve a resolution of the problem. While the main character may have experienced a shipwreck on the way home, she was able to alert a passing ship and therefore made it home in time for her sister’s wedding. These three components reflect the “ABT” framework of storytelling.

Figure 1. Story Arc (Ropp, 2023)

The “ABT” framework, or the “And, But, Therefore” framework, has been used in storytelling for years, even if it was known by another name, such as the Hero’s Journey (Olson 2018:6; The Publication Plan 2020). Before this framework, scientists, including archaeologists, fell into the style of storytelling that was “And, And, And,” where all information was presented but did not provide a narrative for the work. Olson saw the need for more effective science communication; therefore, he brought storytelling to science through the ABT Framework (For more information on the ABT Framework, check out his books and TedTalk).

This framework has been utilized by the SHA Heritage at Risk Committee (HARC), drawing on inspiration from Marcy Rockman and Jakob Maase’s article “Every place has a climate story: finding and sharing climate change stories with cultural heritage” (2017). This article champions the use of the ABT Framework as a way to tell stories integrating climate change and cultural heritage, including tangible archaeological remains.

Since its inception in 2017, HARC has used different platforms to tell the climate stories of cultural heritage. One method is the Heritage at Risk – Climate Stories Pop-Up Exhibit. The pop-up exhibit allows archaeologists to share transformational stories of heritage at risk from our changing climate. As archaeologists worldwide are concerned about the multitudes of impacts that climate change can have on tangible and intangible heritage, the exhibit offers a space for archaeologists to learn from one another and share it with the public. This exhibit features a global collection of case studies highlighting the issue and looking for sustainable solutions. All the case studies within the exhibit utilize the ABT Framework to lay out the narrative of the impacted site, the impacts to the site, and solutions undertaken by professional and avocational archaeologists to combat the impacts.

Figure 2. Pop-Up Exhibit Title Panel and Case Studies (Grinnan 2020)

In 2022, the physical pop-up exhibition expanded to include a digital component. To reach a broader audience, the pop-up exhibit became an ESRI StoryMap. This StoryMap took the contents of the physical display, expanded on the stories of each site, and spatially showed the breadth of climate change impacts, allowing HARC to tell a global story about climate change impacts to cultural heritage.

Figure 3. Title card for the HARC Digital StoryMap (Wholey 2019; photo credit South Carolina DNR).

The current exhibits include case studies from North America and Europe. These case studies cover sites dating from the Archaic period to the mid-twentieth century, with site types ranging from shell middens and shipwrecks to plantations and industrial structures. These case studies provide unique context-dependent climate stories and cross-continent comparative examples of similar climate impacts and management strategies. For example, coastal erosion is a common thread in many current climate stories. This erosion impacts shell middens in Maine and Florida, heritage resources and modern-day communities in Alaska, and fishing and industrial sites across the British Isles. While these different sites face a similar threat, the contributions of the contributing partners to this exhibition provide a variety of techniques that can be applied to other sites worldwide. For example, organizations such as the Florida Public Archaeology Network and CHERISH in Ireland and Wales utilize emerging technologies like terrestrial laser-scanning and unmanned aerial vehicle/drone-based photogrammetry to survey sites. Other initiatives, like the Maine Midden Minders, SCAPE in Scotland, and the Society of Black Archaeologists at the Estate Little Princess in St. Croix, leverage community groups to record sites and conduct assessments before, during, and after large-scale erosion events and hurricanes.

Figure 4. Map of current case study locations (Wholey 2019)

Finally, HARC has sponsored several 3-Minute Climate Story panels at the annual SHA conferences. These panels bring together climate stories from around the world. These stories are told using the ABT Framework and Rockman and Maase’s “Every place has a climate story” themes through a video format. To help make cultural heritage research and climate change impacts more accessible for archaeologists and the public, the video allows archaeologists and heritage professionals to tell the story of a site and share the video across different platforms. This year’s 3-Minute Climate Story panel will focus on Rockman and Maase’s first theme – “Change in the Material World.” This theme makes climate change tangible, focusing on how material culture changes and how archaeologists can identify and monitor this change (Rockman and Maase 2017:110).

These storytelling efforts promoted by HARC represent only a small fraction of the sites at risk and the stories that can be told. As heritage sites are facing these impacts across the globe, we want to help you tell the story of a heritage site at risk from climate change. If you are working on a site at risk from our climate crisis, we would love to help share its story and your work in mitigating the effects! Please complete this Google Form to tell us about your site’s story and share it with the larger archaeological community. Are you unsure if your site fits into our exhibition? Want to participate in a future 3-Minute Climate Story session? Email Allyson Ropp at roppal14@students.ecu.edu for more information.

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Citations:

Olson, Randy

2018    Don’t Be Such a Scientist: Talking Substance in an Age of Style, 2^nd Edition. Island Press, Washington DC.

The Publication Plan

2020    The ABTs of science communication: expert advice from a scientist-turned-filmmaker. The Publication Plan: News for Medical Publication Professionals. https://thepublicationplan.com/2020/11/17/the-abts-of-science-communication-expert-advice-from-a-scientist-turned-filmmaker/. Accessed 7 June 202

Rockman, Marcy and Jakob Maase

2017    Every place has a climate story: finding and sharing climate change stories with cultural heritage. In Public Archaeology and Climate Change, Tom Dawson, Courtney Nimura, Elias Lopez-Romero, and Marie-Yvane Daire, editors, pp. 107-114. Oxbow Books, United Kingdom.

By Susan B.M. Langley, Maryland State Underwater Archaeologist

2023 celebrates the 35^th anniversary of the Maryland Maritime Archaeology Program

In Maryland, April is Archaeology Month and May is Preservation Month, so this is an appropriate time to consider these tiny creatures that pose a large threat to the preservation of submerged archaeological resources. While these marine woodborers have impacted commerce and safety since humanity took to the sea, changes in construction materials of ships and harbor infrastructure, as well as the use of effective but environmentally dubious chemical treatments, greatly reduced their negative effects. There is still a toll; damage to harbor infrastructure by shipworms was estimated at $1 billion USD globally in the early 21st-century (Cobb, 2002) but this still compares favorably to the $500-$900 billion (based on 2009 dollar values) in damage over just two years, 1919-1921, in San Francisco Bay alone (Rayes et al. 2015:488). However, climate change appears to be a factor in the spread and adaptation of these woodborers enabling them to tolerate both fresher and much colder waters and permitting them access to a veritable smorgasbord of historic vessels.

It should be noted that various fungi and bacteria also degrade and rot wood and are the subjects of ongoing studies regarding their effects and the extent to which climate change may be affecting them.  This discussion considers the three main categories of marine woodborers.

Pill Bugs (a.k.a. Roly-Poly, Rollie Pollie, Doodle Bug, Potato Bug, and more) are not insects but terrestrial crustaceans (Figure 1).  Although Armadillidium vulgare is one of the most common, they are so diverse that they are usually referenced by Family; Armadillidiidae.  Although they are crustaceans and breathe through gills they cannot live under water (Reconnect 2023) but live in wet environments like mangroves.  They can damage the latter extensively, which has a bearing on low-lying areas that are coming to rely on mangroves for protection against storms and sea level rise, as well as maritime infrastructure built in these environments.  Because of their larger size compared to the much smaller shipworm and gribble, they were recognized and studied earlier.  They do not eat wood but chew through it to create burrows for shelter and, historically, have had far less impact on ships and harbor structures than the other woodborers. 

Figure 1. Pill Bugs. (Pestworld.org 2023).

It took longer to differentiate gribbles and shipworm because of their small size and the apparent similarity of the damage they caused, despite the gribble being a crustacean and the shipworm being a mollusk.  Both actually digest the wood as opposed to burrowing through it.  There are more than 50 species of marine isopod in the gribble Family Limnoriidae and many of these bore into plants and grasses as well as wood (Figure 2).  The gribble (Limnoria lignorum) as a threat to vessels was identified in 1799.  These are the smallest of the woodborers and leave tiny entry holes that belie the extent of the internal damage they can cause. On the wreck of the vessel believed to be James Cook’s Endeavour off Rhode Island, Reuban Shipway identified both gribbles eating the exterior of the vessel and shipworms devouring the interior of the hull (Kuta, 2022).  A further concern is that as the wood weakens and breaks, creatures that feed on the woodborers can cause additional damage by rooting for them.  There are not a lot of known predators as long as the piece of wood is intact, but when the wood disintegrates, they are rapidly eaten by fishes, crabs, and other predators. They are vulnerable to protozoan parasites, such as Minchinia teredinis, which can cause extensive mortality (Hillman et al. 1990)” (Smithsonian 2023).  Nelson (1925) also suggests the Warty Comb Jelly, or sea walnut (Mnemiopsis leidyi), a species of tentaculate ctenophore, that is known to be a significant predator of mollusk larvae.  Gribbles appear to be native to western Atlantic coastal waters, but have become established as an invasive species in European and western Asian regions.

Figure 2. Gribbles; image on left is 0.5mm (Encyclopedia of Life 2023).

The most infamous of these “termites of the sea” is the shipworm.  While there are a number of species, often named for the regions where they are found, the eponymous Teredo navalis can represent them all (Figure 3).  It does not look like the bivalve it is, because most of its body is external, taking the form of a worm, with the two shells being reduced to small plates at the head designed to auger through wood.  It has been found in fossil form dating from the Cretaceous period (145-66 MYA) but the earliest evidence of them impacting humanity comes from Egypt.  Hull planks from excavations show Teredo damage and efforts to address this through use of thicker planks on oceangoing watercraft versus river vessels, additional sacrificial wood at joints and seams, choices of denser, more finely grained woods like cedar (Cedrus libani) and Nile Acacia (Acacia nilotica), and the application of a coating of pine tar to the hulls (Rayes et al. 2015, Ksenija Borojevic et al. 2010, Polzer 2011, Ward and Zazzaro 2009). So it continued through time, with various coatings being applied; from Pliny the Elder’s reference to zopissa (bee’s wax and resin) to substances like tar, brimstone (sulphur), or arsenic. Then there were efforts to sheath the hulls from additional layers of sacrificial wood to lead sheathing from Greek and Roman times through similar endeavors by Spain and England in the 14^th and 15^th centuries.  The tacks holding the lead sheathing to the hull tended to corrode and the metal then fell off exposing the wood. Japanese boatbuilders even scorched the exterior of the hulls to deter the borers (Thunberg 1796).  Again, there was an effort to find Teredo-resistant wood species.  Two that offered promise were Cuban cedar (Cedrela odorata) and the Cabopa tree (Mitragyna stipulosa) from Cacheu; a region of what is now Guinea-Bissau, and since Spain built about a third of its Navy in Cuba in the 18^th century this connection demonstrates the merit of studying placement of shipyards in proximity to where teredo-resistant timbers grew (Aderinto 2007, McNeill 2004). Copper sheathing had its first success when applied to the Royal Navy vessel Alarm in 1761 and became widespread thereafter whenever a builder could afford it.  The late 19^th and 20^th centuries saw a return to applied coatings, but of metallic anti-fouling paints of significant toxicity including mercury, and chrome copper arsenate, as well as somewhat less toxic turpentine and borax, although these are still undesirable (Paalvast and van der Velde2011) and most were outlawed by the late 20^th-century.  The widespread use of ferro-concrete in harbor structures after 1900 also aided in reducing damage.  In the 20^th-century, increased Teredo activity was experienced by urban and developed areas after steps were implemented to reduce the level of pollution in the waters.  New York City, after the Clean Water Act of 1972, saw improved water quality but also extensive woodborer damage between 1995-1997 such that a 21-meter(23-yard) section of a wharf dropped into the East River, and a 6-meter (6.6-yard) section fell from the Brooklyn pier (Rayes et al. 2015:488, Paalvast and van der Velde 2011:119). Similar situations have occurred in Maine in 2000, on the Rhine River and in the port of Rotterdam (Cobb 2002), and are currently occurring in Venice (Figure 4).  Ironically, pollution had been protecting these and, by extension, submerged heritage resources.

Figure 3. Teredo navalis (David Fickling 2020).

 

Figure 4. Teredo damage to a wharf in Venice (Langley 2022).

The origins of these marine woodborers are not clear since they were not studied until they became a threat.  Pill Bugs are believed to have originated in southern Europe and/or northern Africa (Higgins 2023).  Gribbles, as previously, noted, are native to the western Atlantic but Teredo are thought to have originated in the Pacific and Indian Oceans (WreckProtect 2023).  As they were in Egypt’s harbors so early, it may speak to their introduction to the Mediterranean via vessels brought overland from Egypt’s Red Sea/Indian Ocean trading and fishing expeditions and, like most invasives, they spread rapidly.  The introduction and widespread proliferation of shipworm outside of the Mediterranean correlates with the expansion of European maritime trade into the Indian Ocean and subsequently to the Caribbean and beyond.  Although they are considered warm water species, they adapted sufficiently rapidly to Atlantic waters to force the beaching of the vessels Capitana and Santiago during Columbus’s fourth voyage, in 1503.  In 1731, they caused extensive damage to the wooden seawalls holding back the ocean from the reclaimed lands of The Netherlands and kept the citizens living in fear of a disastrous flood for the two years it took to repair and reinforce the seawalls.  In an 1873 publication about the laying of communications cables, Sir James Anderson, complained about them boring through the core of the cable in shallow water, and devouring the hemp covering in a few months and inhabiting the interior gutta-percha covering at depths of 2.2 km (1.37 mi) and said that the only protection was burying the cables but noting that they could not be relied upon to stay buried (Anderson 1873).

Conventional wisdom has been that shipworm requires warm salty water to survive and this seemed to hold for the Mediterranean where ship remains only survived if they were buried or covered by cargo like amphorae.  Cold, more brackish, waters preserved vessels beautifully, as is evident in the myriad vessels in the Baltic Sea.  However, more recently it has become apparent that climate change is increasing salinity, as well as warming the waters, of the Baltic (WreckProtect) and, also, many European Rivers are experiencing a migration of salinity upstream (Paalvat and van der Velde 2011:120).  Species of Teredo are also adapting to tolerate much colder and fresher waters.   This has been reported by WreckProtect during a two-year project funded by the European Union between 2009-2011.  Also, a log was recovered by a research vessel from 250 m (273 yards) depth and only 1100 km (683 miles) from the North Pole and with a water temperature of -1.8°C (28.8°F) that was riddled with a living multi-generational colony of Teredo (Kintisch 2016).

The Chesapeake Bay covers an area of 4,479 square miles in both Maryland and Virginia, with five major rivers in Maryland and a further 111 square miles of State coastal waters.  Certainly, climate change is evident and being addressed through the State’s Climate Change Program and its sub-programs. However, Teredo and another woodborer present in the Bay, Bankia Gouldi L., are not considered in these.  Most of the studies of shipworm in Maryland date from the early 1950s (Maryland Tidewater News 1951, Schelema and Truitt 1956). The average depth of the Bay, outside of the 80-foot deep shipping channel, is about 45 feet, which means it is heating very rapidly; 1°C (1.8°F) over the last 30 years (NOAA 2023).  This is already being expressed in the proliferation of the flesh-eating bacteria Vibrio vulnificus (NOAA 2022).  At present, submerged historic resources in Baltimore Harbor may be benefitting from the double-edged sword of the extant pollutants, but the more than 5000 wrecks in Maryland waters are increasingly at risk.  Until more studies are undertaken, the best resources available for managing the maritime resources are the detailed manuals produced by WreckProtect which offer guidelines for protecting submerged wooden cultural sites (2011a) and guidelines for predicting shipworm damage (2011b).  Although the latter focuses on the Baltic, it is relatively recent and can be adapted.  While it will take time for the 100 WWI vessels in the Mallows Bay-Potomac River National Marine Sanctuary to be under direct threat from shipworm, it may be sooner than anticipated.  It would be a sad irony for ships that faced all the challenges of seafaring with storms, reefs, and battles, to be lost to a 15mm (0.5 inch) mollusk.

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Citations:

Aderinto, Saheed. 2007. “Shipyards,” T. Falola and A. Warnock (eds.). Encyclopedia of the Middle Passage. Greenwood Press: Westport, CT. Pp.343-344
Anderson, James. 1873. “Ocean Cables,” The Popular Science Monthly 3:41.

Borojevic, Ksenija, Warren Steiner, Rainer Gerisch, Chiara Zazzaro and Cheryl Ward. 2010. “Pests in an Ancient Egyptian Harbour,” Journal of Archaeological Science 37(10):2449-2458.
Cobb, Kristin. 2002. “Return of a Castaway,” Science News 162:7-74.

Encyclopedia of Life. 2023. Image of Gribbles. Accessed May 14, 2023: https://eol.org/pages/7300

Fickling, David. 2020. “The naval shipworm Teredo navalis is an under-appreciated marker of globalization.” Twitter post Dec. 30, 2020.

Higgins, Lila. 2023. “Nature Gardens Pill Bugs.” National History Museum, Los Angeles County. Accessed: May 14, 2023. https://nhm.org/stories/nature-gardens-pill-bugs#:~:text=An%20Introduction,southern%20Europe%20and%20northern%20Africa.

Hillman, Robert. Susan Ford, Harold Haskin. 1990. “Minchinia teredinis n. sp. (Balanosporida, Haplosporidiidae), a parasite of teredinid shipworms,” Journal of Protozoology 37(5): 364-368.

Kintisch, Eli. 2016. “Arctic shipworm discovery alarms archaeologists,” Science 351(6276): 901.

Kuta, Sarah. “Shipworms Are Eating a Wreck That Could Be Captain Cook’s ‘Endeavour’” Daily Correspondent. August 18, 2022.

Langley, Susan. 2022. Image of Teredo damage in Venice, Italy.

Maryland Tidewater News. 1051. “Ship Worm Study Advances,” Maryland Tidewater News 8(7):1.

McNeill, J. 2004. “Woods and Warfare in World History,” Environmental History 9(3):398.

Nelson, T.C. 1925. “On the occurrence and food habits of ctenophores in New Jersey inland coastal waters” Biological Bulletin 48:92-111.

NOAA. Accessed May 14, 2023: https://www.fisheries.noaa.gov/topic/chesapeake-bay/climate-change

NOAA. 2022. Accessed May 14, 2023: https://coastalscience.noaa.gov/news/noaa-forecast-predicts-occurrence-of-pathogenic-vibrio-bacteria-in-chesapeake-bay-in-2022/

Paalvast, Peter and Gerard van der Velde. 2011. “New Threats of an old enemy: The distribution of the shipworm Teredo navalis L. (Bivalvia: Teredinidae) related to climate change in the Port of Rotterdam area, The Netherlands,” Marine Pollution Bulletin 62(2011):1822-1829.

Pest World. 2023. Image of Pill Bugs. Accessed May 14, 2023: https://www.pestworld.org/pest-guide/occasional-invaders/pillbugs/

Polzer, Mark. 2011. “Early Shipbuilding in the Eastern Mediterranean,” A. Catsambis, B. Ford, and D. Hamilton (eds.) The Oxford Handbook of Maritime Archaeology. Oxford University Press: NY. Pp. 349-378.

Rayes, Courtney, James Beattie, and Ian Duggan. 2015. “Boring Through History: An Environmental History of the Extent, Impact and Management of Marine Woodborers in a Global and Local Context, 500BCE to 1930s CE,” Environment and History 21(4):477-512.

Reconnect. Reconnect with Nature. The Nature Foundation of Will County, Illinois. https://www.reconnectwithnature.org/news-events/the-buzz/roly-poly-pill-bugs/ Accessed May 14 2023.

Scheltma, Rudolf and R.V. Truitt. 1956. “The Shipworm Teredo navalis in Maryland Coastal Waters,” Ecology 37(4):841-843.

Smithsonian Nemesis. Marine Invasions Lab. “Teredo navalis.” Accessed May 14, 2023: https://invasions.si.edu/nemesis/species_summary/81862

Ward, Cheryl and Chiara Zazzaro. 2009. “Evidence for Pharaonic Seagoing Ships at Mersa/Wadi Gawasis, Egypt,” The International Journal of Nautical Archaeology 39:27-43.

World Economic Forum. 2018. Image of Gribbles. https://www.weforum.org/agenda/2018/12/a-tiny-crustacean-could-help-us-create-biofuel-from-wood/

WreckProtect. 2023. Home Page. Accessed: May 9, 2023. http://wreckprotect.org/

2011a. “Guidelines for the Protection of Submerged Wooden Cultural Heritage,” Accessed May 14, 2023.

http://wreckprotect.org/fileadmin/site_upload/wreck_protect/pdf/Guidelines_Protection_web.pdf

2011b. “Guidelines for Predicting Decay by Shipworm in the Baltic Sea,” Accessed May 14, 2023.

http://wreckprotect.org/fileadmin/site_upload/wreck_protect/pdf/Guidelines_Predicting_web_1.PDF

By Lindsey Cochran, Assistant Professor, East Tennessee State University; Grant Snitker, Director of the Cultural Resource Sciences and Fire Lab, New Mexico Consortium

An urgent question for archaeologists as we race to react to the climate crisis is: what are we losing? The biased nature of the collective archaeological dataset presents an unequal assessment of heritage at risk. As we know, today’s cultural landscape boundaries are different than those in the past. The majority of known cultural heritage sites are driven by cultural resource management and compliance, meaning known sites are often located near roadways, pipelines, reservoirs, and military installations. We propose that in addition to assessing which cultural heritage sites are at risk, archaeologists should also work to understand how under-investigated landscapes contribute to how we evaluate landscapes most likely to change enough to threaten, damage, or destroy our ability to interpret the past for future generations.

Figure 1. An optimized hot spot analysis of the relative densities of known archaeological sites in Georgia, USA. This map shows statistically significant hot and cold spots of identified archaeological sites using the Getis-Ord Gi* statistic. The red hotspot is Fort Stewart Army Base where NHPA catalyzed a fuller survey of cultural resources. Cells with no value indicate an absence of documented archaeology sites. Cells represent density of known sites within that hexagon, not site locations.

Within those known sites, archaeologists most often only excavate a small fraction of an area where people may have left cultural materials behind. Of those, only a few certain materials persist over time and are available for recovery. So when we ask “which non-renewable cultural heritage resources are we losing” because the climate emergency, the answer is that we’re not really sure.  Rather than using only the things people left behind, we propose to leverage the bias inherent in archaeology: non-uniform excavation strategies within and between sites, and differential preservation of material culture, by using historical maps to supplement the places in-between excavations.

Historical maps allow archaeologists to gain a greater understanding of how past people viewed and navigated the world around them. However, these documents were created by people and for a purpose, meaning that historical maps depicting the same place at the same time, but created by different people, can tell dramatically different stories. Despite an element of inherent bias, historical maps are a tether to, at minimum, a cultural understanding a landscape and the potential presence of previously undocumented archaeological resources.

Here, we propose to leverage our biases: What could be known that we haven’t thought to investigate (yet)? For example, on the coast of Georgia, USA, can we use historical maps to estimate the location of resources that have little or no documentation, specifically Irish landholdings, farmsteads, small plantations? What elements of the landscape influence the presence or absence of a resource that has not yet been archaeologically documented?

We propose that historical documents, specifically historical maps, can be used as input data to investigate where significant archaeological sites may be located, the landscapes they occupy, and what future risks form climate change they might experience.  

Then, machine learning algorithms can be used to identify places on the landscape where there may be very significant cultural heritage resources that we are unaware of. These locations can then be cross-referenced with NOAA models of climate change or an archaeological triage assessment of those models to identify which potentially significant areas should be first surveyed prior to probable destruction.

Our case study is from a coastal t-sheet from Sapelo Island, Georgia, USA created by H.S. DuVal in 1857 and reported to his superintendent, A.W. Evans in the same year. Alone, these documents contain useful information about how the landscape has changed over the last 200+ years. One such example is a simple note: “A new channel developed leading into Sapelo sound, Ga., three-quarters of a mile southward, and better than the one in use, 1860” (1863:78). The reconnaissance map maker is potentially indicating the new use of the Cabretta inlet, which is now undergoing rapid change. The report of DuVal to Evans also contains useful information about the cultural context of the survey—plantation owner Thomas Spalding hosted DuVal and encouraged him to place one of his five transect lines through the Gullah-Geechee Behavior Settlement.

Proof of Concept Methodological Steps

In this proof-of-concept study, we georectify and vectorize elements of the historical landscape that were noted by the reconnaissance surveyor that could have influenced the presence or absence of an historical site. Those elements are then used as testing and training samples to determine if there are relatively standard cultural and environmental landscape attributes that can be used to determine is likelihood of the presence or absence of a plantation site on the Georgia coast.

We have established four basic steps to this machine-learning methods for identifying plantation sites using datasets derived from historical maps:

1. Georectify the historic map to place it into real space.

Figure 2. Location of Sapelo Island, Georgia with the DuVal (1857) reconnaissance map georectified to the modern landscape.

2. Digitize model inputs within the landscape using archaeological experiences like pedestrian surveys and Phase I/II surveys, historical sources, and expert inputs to create landscape variables. In this case, we used vector inputs within the computational extent of the project area, vegetated areas, potentially arable land, proximity to structures, proximity to roads, and proximity to other cultural features (Figure 3).

Figure 3. Binary and continuous variables for classification into the machine learning algorithm.

3. Create a training set for the random forest classifier. A random forest classifier is a supervised machine learning algorithm that essentially grows multiple uncorrelated decision trees (Figure 4). After training samples are run through the many decision trees, results are aggregated into a majority class. The benefits of a random forest classifier are that the estimates fit a number of decision trees and sub-samples of the data to improve accuracy of the model and reduce over-fitting the training samples (Figure 5).

Figure 4. Random forest classifier in machine learning. (Image from https://www.tibco.com/reference-center/what-is-a-random-forest)

Figure 5. Testing versus training inputs, closeup of the Spalding Sugar Plantation, Sapelo Island, Georgia, USA

4. Classify the entire landscape based on the training results (Figure 6).

Figure 6. Results of the random forest classifier. Yellow indicates a high probability of the presence of an element of a plantation site, whereas blue indicates a high probability of the absence of a similar site.

Overall, the model performs well to identify already known and potential plantation sites and activity areas within our study landscape. The model processing and production took place in R, which means that the processing steps and code is freely available, shareable, adaptable, and replicable. Finally, we are working to automate the digitization and vectorization process. However, because the historical map-makers are human, each map contains elements that need to be interpreted by a human. A computer might interpret the ink blot highlighted in Figure 7 as a structure, rather than an accidental mark made by the mapmaker.  While this process was time intensive and limited to what is observed in each map, the next steps of this project are to expand our case studies beyond Georgia’s barrier islands and to the more inland sites that have been the subject of fewer or no studies at all.

Figure 7. A red circle is around a selection of archaeologically verified slave cabin, whereas the blue squares are around ink-blots pretending to be archaeologically significant.

Conclusion

What makes archaeology so interesting to us is that the nature of archaeology prohibits a complete understanding of our data. The puzzle will always remain a puzzle, but ideally with fewer missing pieces as research projects continue. Despite the ever-incomplete nature of our discipline, historical archaeologists have a unique relationship with a dataset uncommonly used when researching heritage at risk sites.

We propose the development of a carefully interpreted machine learning approach, such as the one presented here, for using existing datasets in a new way to address a developing crisis. A create reinterpretation of existing data may facilitate our disciplinary creation of endangered sites lists that include probabilities of an area to contain as-of-yet undocumented resources. We suggest that a part of our response to the climate emergency includes a conversation about prioritization: should we direct more resources to preserving sites that what we already know about or to identify what we could know but may never have the chance to know.

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Citations:

Bache, A.D.

1864     Report of the Superintendent of the Coast Survey, Showing the Progress of the Survey during the Year 1863. Washington Government Printing Office. Washington, D.C. Accessed 6 Feb 2023. <https://library.oarcloud.noaa.gov/docs.lib/htdocs/rescue/cgs/001_pdf/CSC-0012.PDF>

DuVal, H. S.

1857 Topographical Reconnaissance of Sapelo Island, Georgia. United States Coastal Survey, A. D. Bache, Superintendent. Atlanta: Surveyor General Department, Office of the Georgia Secretary of State. https://nosimagery.noaa.gov/images/shoreline_surveys/survey_scans

Evans, A.W.

1857 Letter of the Secretary of the Treasury, Communicating the Report of the Superintendent of the Coast Survey, Showing the Progress of That Work During the Year Ending November 1, 1857. Appendix No. 39: 347-377.  <ftp://ftp.library.noaa.gov/docs.lib/ht-docs/ rescue/cgs/001_pdf/CSC-0006.PDF>.