https://orcid.org/0000-0001-8312-7928
Abstract
Integration of natural and cultural resource management is urgently needed to combat the effects of climate change. Scientists must contend with how human-induced climate change and rapid population expansion are fundamentally reworking densely inhabited coastal zones. We propose that a merger of archaeology, environmental science, and land management policy—different yet intertwined domains—is needed to address dramatic losses to biocultural resources that comprise coupled cultural-natural systems. We demonstrate the urgency of such approaches through analyses of coastal archaeological regions within the U.S. Atlantic and Gulf coasts where sea level rise is a primary threat, and we extend our findings globally through an assessment of primary risk factors and forecasts for archaeological sites in the Netherlands, Peru, and Oceania. Results show that across the U.S. Gulf Coast and in Oceania, where little hard infrastructure is in place to protect archaeological sites, hundreds of low-lying coastal sites will be lost under future climate scenarios. In other coasts, like that of the Rhine-Meuse Delta (the Netherlands), risks range from erosion caused by periods of flooding to the degradation of wetland sites caused by extreme droughts. In coastal Peru, population pressures pose the primary risk to archaeological sites through rapid agro-industrial growth, urban expansion, and El Niño climate variability. Across all risks, we propose that management strategies to mitigate losses to biocultural resources must be approached as a restoration process of linked sociocultural and physical environmental systems.
Introduction
Extreme weather events and the cascading effects of climate change are among the most pressing natural and cultural resource management issues affecting our rapidly changing world (1–3,). For example, catastrophic flooding inundated much of southeastern Spain in October 2024, and yet one town, Almonacid de la Cuba, was saved from much of the damage due to a 2,000-year-old Roman dam (4). Weeks prior, in late September 2024, unprecedented flooding from Hurricane Helene decimated the southern Appalachian Mountains in the United States, causing more than 200 deaths and $78.7 billion in damage (5). In the Horn of Africa, long-term cycles of drought have been linked to rapidly changing land-use patterns impacting evapotranspiration (6). Scientists estimate the cost of extreme weather in the United States to be $143 billion per year (7), with a global cost of more than $2 trillion dollars in the past decade (8). Yet, natural and cultural resource management remain siloed into separate monodisciplinary research and management systems, hindering our ability to synergistically tackle these issues. Indigenous worldviews remind us that the human worlds and the natural world are not distinct phenomena (9–11). Consequently, we should not forget the influence ancient societies exerted in creating archaeological landscapes that are fundamentally inseparable from the natural world [e.g. (12)].
In practice, the artificial separation of cultural and natural domains negatively impacts the preservation and restoration of biocultural resources like coastal archaeological landscapes that are inherently coupled systems (13, 14). Ecological restoration grounded in anthropological theory (15–18) acknowledges all environments have been influenced by human development and that no “pristine’ state exists today [e.g. (19)]. Consequently, choosing a restoration point to target must be accomplished by identifying precolonial landscapes and ancient landscape modifications, and incorporating those Indigenous frameworks into natural resource management protocols (20–22). Yet, the tangible archaeological archives that facilitate such knowledge are broadly endangered and rapidly disappearing from modern landscapes.
This paper assesses archaeological site vulnerabilities to environmental change as they vary by region (Fig. 1) and provides a framework for integrating natural and cultural resource management from the perspective of coastal archaeological sites and biocultural resources. We consider coastal biocultural resources to be marshes, deltas, littorals, and other coastal features alongside their nested and often persistent human adaptations and associations, most notably archaeological sites. We focus first on U.S. passive-margin coasts, primarily within the states of Louisiana and Florida (U.S. Gulf Coast) as especially vulnerable coastal systems. We then extend our assessment to comparative examples worldwide drawn from the Rhine-Meuse Delta of the Netherlands, Pacific islands of Oceania, and northern desert coast of Peru. The main focus of the paper is on archaeological sites, even though we are aware that cultural resources include a wider variety of heritage assets, and we occasionally touch on this diversity as well.
Modern population density at selected coastal locations where archaeological sites are at risk of inundation and other threats. This study focuses on (A) the Mississippi River Delta and (B) the Florida Big Bend of the U.S. Gulf Coast, (C) coastal Peru, (D) the Rhine-Meuse Delta, and (E) the Hawaiian Islands and (F) New Zealand (Aotearoa) of Oceania. The global map depicts lighting at night, a proxy for habitation/industrialization, and panels a-e show population density at the study foci as indicated in the color scale. Images modified from https://hub.arcgis.com/maps/esri::earth-at-night and https://luminocity3d.org/WorldPopDen.
Our research confirms that site loss is rapid, acute, and ongoing. We contend that cultural heritage, cultural patrimony, and our shared and collective archaeological heritage is a fundamental part of who we are as humans, and that losing archaeological sites that comprise our heritage is akin to losing pieces of ourselves and our history (23). It is vital that we strive to maintain Indigenous cultural patrimony, which is the ongoing relevance and importance of history, tradition, culture, and identity through archaeological sites, artifacts, and objects of cultural value. Cultural sites, like museums, archives, libraries, and schools, are places where memory is retained through artifacts and archaeological contexts, through personal experiences during a visit, and through the ways in which they influence our understanding of identity, culture, and affiliation (24). These sites are not mundane assemblages of artifacts, but rather are irreplaceable keys to archaeological and ecological knowledge as well as core components of local, Indigenous, national, and world heritage identities.
Coastal regions and waterways have long been the geographic nuclei of humanity, evidenced for example by the coeval emergence of Earth's Holocene deltas alongside ancient societies [e.g. (25)] as well as their present-day population density, often centered in large coastal cities (Fig. 1). Effective modern governance of coastal landscapes requires interdisciplinary approaches due to their natural abundance, high population pressures, and challenging outlook—properties that inherently couple the natural (physical sciences) and cultural (social science) domains [e.g. (26, 27)]. With growing local awareness of how climate-driven sea level rise (SLR) is exacerbating erosion, land loss, and cultural site loss, federal coastal management agencies within the U.S. like the National Oceanic and Atmospheric Administration (NOAA) and the Bureau of Ocean Energy Management, and nonprofit organizations like the Coalition to Restore Coastal Louisiana and others across the United States, and the globe, like UNESCO and the Cultural Heritage Agency of the Netherlands, have initiated projects driven around both historic preservation, landscape restoration, and erosion abatement (28–32).
Immediate threats to coastal biocultural resources are widely documented, and suggestions have been offered to mitigate climate change threats (13, 26, 27, 33–41). Unfortunately, federal cultural resource initiatives within the United States have not sufficiently adapted or integrated climate change and natural resources into their organizational structure (26). As Rockman and Hritz (27) noted, there is a discrepancy between federal funding and infrastructure provided for natural resource management as opposed to cultural resource management. Here, we suggest that a more thorough integration of cultural heritage within environmental science and land management policies beyond regulatory compliance mandates provide one solution to this problem.
The U.S. Gulf Coast, especially within coastal Louisiana, is an ideal location to employ much needed integrated cultural-natural resource management approaches. Coastal Louisiana boasts diverse cultural resources, from ancient Indigenous sites to Colonial-era settlements representing a unique blend of Indigenous, African American, Caribbean, Acadian, French Creole, and Spanish influences. These often overlooked stories are crucial to America's cultural narrative and deserve preservation. Environmentally, the region faces numerous challenges including wetland loss, subsidence, SLR, hurricanes, high population density, and industrial activities. Over US$50 billion have been allocated to improve the condition of the Gulf Coast through the RESTORE Act (31 CFR 34), one of the largest environmental fines ever levied in history (42). A unified coastal management approach outlined in the government-designed and science-based Coastal Master Plan (43) are dedicated to combat Louisiana's coastal challenges. Yet, the area's rich archaeological heritage remains at great risk. While billions in environmental fines have been allocated for ecosystem restoration along the U.S. Gulf Coast, these funds rarely address cultural resources, and there is no explicit cultural resources management strategy, for example, in Louisiana's Coastal Master Plan. Despite calls to action, there remains little direct federal intervention on preservation of coastal cultural resources, with the exception of the most recent 2021 Infrastructure Investment and Jobs Act (44), which only indirectly addresses climate, resiliency, and cultural resources mitigation through regulatory mechanisms.
Cultural resource management is conducted through federally mandated regulatory compliance under the National Historic Preservation Act of 1966. The National Historic Preservation Act of 1966 stipulates that impacts to cultural resources must be considered as part of any federally funded undertaking with potential for (sub)surface ground impacts. As such, cultural resources are typically only considered on the back end of projects from the perspective of impacts from a landscape restoration project itself, rather than being part of overall project goals. Here, we suggest that cultural resources should be baked into coastal restoration strategies from the outset as a key component of coupled natural and cultural systems,
Archaeological site vulnerability in eastern and southern coastal United States
Recent analyses of the passive-margin Atlantic and Gulf coasts of the United States highlight the need for a coordinated effort “like that seen in the Great Depression (when unprecedented federal efforts were undertaken to conduct salvage archaeology through public works), to document that which (archaeological sites) will be lost if the effects of sea level rise are not mitigated” (33). An analysis of SLR impacts to coastal archaeological sites, historic properties, and other places of cultural significance on the Gulf and Atlantic coasts of the southeastern United States (33) showed that 5,762 sites are presently located at or below sea level (33). At current sea level projections (45), 19,676 known Atlantic and Gulf coast archaeological sites will be underwater by 2100 (33). Projecting against modern population data (46), they model a potential impact to over 3 million Americans living at elevations <1 m above mean sea level and an additional ∼3.5 million living between 1 and 2 m above mean sea level.
SLR impacts are not felt equally along coasts due to their varying topography and substrates, habitation patterns, and dynamic processes. Island landscapes like the Florida Keys experience flooding and erosion differently than the Florida Big Bend, which has high-elevation topographic features like the Cody Scarp and deeply incised rivers adjacent to a low lying coastal plain. Nevertheless, Indigenous archaeological sites are numerous in the Florida Big Bend, and there can still be many losses of the most coastward, low-elevation sites (34). In the Mississippi River Delta of southeastern Louisiana, an extremely low-lying deltaic landscape, land loss, erosion, subsidence, and SLR continue to impact archaeological sites and landscapes dramatically (47). Along this passive margin, thick sedimentary sequences have accumulated to build a low gradient delta plain. The flat expanse of topography (48) in combination with shallow compaction of Holocene strata [e.g. (49, 50)] can enhance the vulnerability of Mississippi River Delta cultural heritage sites to storm surge and relative sea-level rise (rSLR) impacts. The local variance of landscapes including their dynamic processes, topography, and ultimately vulnerability, necessitates new in-depth analyses for sea-level risks to archaeological sites at a regional scale.
We utilized LiDAR digital elevation models, site location data, and NOAA SLR models to define impacts and inundation of archaeological sites for the U.S. Gulf Coast regions of the Florida Big Bend and the Mississippi River Delta. For the Florida Big Bend (11,000 km2), our modeling demonstrates 11 Indigenous sites dating from the beginning of the first millennium CE until just before European contact are already at or below current sea levels (see Supplemental Information S1 and Table S1 for data tables and Materials and Methods). With 1 m of SLR anticipated for the next century (51), 142 additional and different mound and midden sites will become vulnerable to submergence (Fig. 2B, C). This is more than a 10-fold projected increase. Impacted sites would include Garden Patch (Fig. 2B), an Indigenous monumental complex with 6 earthen mounds and considerable potential for future study. Researchers have barely uncovered the political, economic, and social dynamics of this civic ceremonial center (52–55). Unfortunately, with just 1.5 m SLR, much of the low-lying portions of the site will be inundated and/or eroded away through tidal fluctuations and wave-action at the new coastline.
Vulnerability to SLR of indigenous archaeological sites in (A) the Mississippi River Delta and (B) the Florida Big Bend of the U.S. Gulf Coast. (C) For these regions, the cumulative number of sites below mean sea level is projected for SLR up to 3 m. Filled circles indicate cumulative values, and open circles indicate incremental values. The sites of Garden Patch (GP), Magnolia Mound (MM), Bayou Grand Cheniere (GC), and Adams Bay (AB) are indicated by open white rectangles. (Images A and B created by Tara Skipton).
The NOAA Sentinel Site Cooperative (56) estimates that the Mississippi River Delta will experience 1 m SLR by 2060, sooner than Intergovernmental Panel on Climate Change global estimates. This is mostly due to the ephemeral nature of Louisiana's coastal marshes already impacted by oil exploration and subsidence [e.g. (57)]. Along 25 coastal parishes in southeastern Louisiana, we identified 11 known Indigenous archaeological sites at or below current sea levels. Our modeling indicates that the 1 m SLR forecast by 2060 will endanger 107 Indigenous mound and midden sites (Fig. 2A, C). Terrebonne, Jefferson, Lafourche, and St. Bernard parishes will experience the most significant vulnerability of losses. Geomorphically, these parishes are built upon relict lobes of the Holocene Mississippi River Delta [e.g. (58, 59)] and they make up much of the Mississippi River Delta (MRD) in the coastal zone. These relict regions of the delta have the lowest-lying topography, no longer receive sediment to offset relative SLR, and are experiencing erosion and subsidence (49, 60). At risk are Indigenous monumental landscapes like the Magnolia Mounds complex (Fig. 2A) and the Bayou Grand Cheniere site (Fig. 2A), two understudied multimound civic-ceremonial centers that are notable for their scale and complexity for monuments built by largely egalitarian hunter-gatherers (13, 38, 47, 59, 61–66). Well-known Indigenous monumental complexes like Adams Bay (www.adamsbayproject.org) (Fig. 2A) are documented in more detail but well on their way to being completely inundated (14, 63).
These estimates inform vulnerability to SLR based on a “bathtub’ scenario that does not account for leveeing/impounding of the coast or local hurricane impacts [e.g. (67)]. While many sites are protected from inundation by hard infrastructure within the highly modified Louisiana coast, these measures are not foolproof. Coastal Louisiana is underlain by a thick succession of deltaic muds and sands that offer relatively low permeability compared with the karstic landscape of the Big Bend region of Florida, meaning that levees and sea walls have a chance at stopping or postponing the ingression of coastal waters. Yet, levees are not a failsafe, especially in an environment with high-energy tropical storms and cyclones like the U.S. Gulf Coast [e.g. (68)]. As sea level rises, coastal infrastructure is likely to experience increased strain. The anticipated result is that even impounded coastal sites become increasingly vulnerable to future inundation. For example, a levee breach or other flooding during a high-magnitude storm event would drive rapid, catastrophic loss of numerous sites (67).
Marine impacts are not limited to the immediate coastline. In 2020, Hurricane Laura made landfall as a Category 4 hurricane off the coast of western Louisiana, followed just 2 weeks later by Hurricane Delta, a Category 2 hurricane that took a very similar path into already weakened environments. Hurricane Laura recorded the strongest hurricane winds to hit Louisiana since 1856 and was novel in that it sustained hurricane-force winds over 100 miles inland, resulting in unprecedented damage to upland environments even less resilient to coastal extreme weather events. More than 800,000 acres of timber were destroyed by these storms (69). Much of the impact occurred within Kisatchie National Forest, a protected area encompassing 605,000 acres in north-central Louisiana, ∼150 linear km inland from the coast (Fig. 2A). Here, hundreds of archaeological sites were significantly damaged by uprooted trees, necessitating more than $1 million in archaeological data salvage (70). Hurricanes Laura and Delta illustrate the expanding range of coastal climate change impacts as storms intensify in numbers and severity and coastal buffers like wetlands continue to be lost.
Primary risk factors in other coasts and regions
While sea level is of clear importance to archaeological site risk in the U.S. Gulf and Atlantic Coasts, other factors can influence site risk: here, we assess primary risks in select coasts outside the United States.
The Rhine-Meuse delta, the Netherlands: flooding, erosion, and drought
The Netherlands has always been a highly dynamic, predominantly low-lying country (71). Coastal areas consist of an elongated series of dunes and beach ridges, with behind them vast stretches of tidal flats, salt marshes, peatlands and the floodplains of the Rhine-Meuse delta. A significant part of these wetland areas are situated below sea level (Fig. 3A), and the wetlands have been drained and embanked from circa 1000 CE onward (73). The rich cultural heritage of the coastal and other low-lying parts of the Netherlands is highly diverse, ranging from prehistoric waterlogged archaeological sites to ancient dykes and mounds, and reflects its history and identity (74). Different potential climate scenarios have been developed for the Netherlands (75), the potential effects of which are presented in a national-scale interactive “climate effect atlas” (https://www.klimaateffectatlas.nl/nl/). Currently, various regional “climate stress tests” are being conducted, which aim to analyze the vulnerability of an area to SLR, flooding, extreme weather events, heat and drought and may form input for climate adaptation and mitigation strategies (https://klimaatadaptatienederland.nl/stresstest/monitor/).
(A) Despite a significant portion of the Netherlands lying below sea level, inundation risk to archaeological sites is relatively limited here by (B) an extensive network of dikes. (A and B) Images modified from Haasnoot et al. (72) and the map “Living with Water” (https://rce.webgis.nl/nl/map/leven-met-water) maintained by the Dutch Cultural Heritage Agency (72). NAP, Normaal Amsterdams Peil.
The Cultural Heritage Agency of the Netherlands has recently performed a national-scale quick-scan of the vulnerability of cultural heritage for the effects of climate change, making a distinction between the domains of archaeology, built heritage, immaterial heritage, cultural landscapes, and cultural collections (https://storymaps.arcgis.com/stories/02252ae6ffcc4e178577eab18ff59035). A wide variety of potential threats are identified. These range from damage and erosion of heritage sites caused by flooding to periods of extreme drought leading to degradation of waterlogged archaeological sites in peatlands. Compared with the other regions under study in this paper, the direct effects of SLR are expected to be less severe because of major past investments in dikes (Fig. 3B), dams, and storm surge barriers along the Dutch coast (76). However, they will probably lead to increased wetness and salinization of drained landscapes and require major further investments in dyke reinforcements.
Despite the first positive steps taken to investigate potential consequences of accelerating climate change and landscape dynamics, clear regulations or policies for climate change adaptation for cultural heritage still need to be developed (77). Cultural heritage sites are not consistently incorporated in existing climate and spatial adaptation policies, such as the National Delta Programme (78). Recent studies have stressed that culturally rich and fragile Dutch wetland sites, such as the UNESCO World Heritage sites of the Wadden Sea and Schokland, result from an intricate combination of physical geography, biology, and cultural history, and should be managed from a holistic point of view (79, 80). This requires the bridging of institutional silos and enhancement of coordination among relevant institutions and actors (77).
Oceania: SLR and natural disasters
It is hard to imagine a region that will be impacted by SLR more directly than the islands of the Pacific. However, progress on documenting, predicting, and mitigating the impacts to cultural heritage in Oceania has been frustratingly slow. For example, Johnson et al. (81) raised the alarm on how SLR will inundate Pu‘uhonua on Honaunau National Historical Park on Hawai‘i Island, a U.S. National Park with impressive ancient architecture that draws in 300,000 visitors per year. As one of the few examples of a well-preserved Hawaiian royal center, it is a location of enormous cultural and historical importance, but in this case, it was not the looming impacts of SLR that initiated their study. A 2011 tsunami event that temporarily flooded the coastline instigated this study that foreshadows the long-term trajectory damage to cultural heritage.
Episodic disasters not only generate immediate attention, they also hold the potential to promote new lines of scientific research. Elsewhere on Hawai‘i Island, storm damage to a known coastal site in 2016 instigated salvage excavations as part of stabilization efforts (82). An analysis of the midden deposits recovered was undertaken in the hopes that they might inform us about the earliest periods of human settlement in the archipelago. In that specific case, salvage excavations did not produce the hoped-for early deposits, but cumulatively, similar coastal excavations have significantly shaped our picture of the long-term human history of the Hawaiian Islands (83).
Postdisaster studies like the previous examples have not translated into more systematic long-term planning around SLR in Oceania, in part, because they focus on individual locations, rather than on the entire coastline. In a review on how archaeologists are addressing the challenges of SLR with different geospatial technologies (remote sensing, high-resolution documentation, geodatabases), McCoy (84) examined the problem of SLR across New Zealand (Aotearoa) (Fig. 4). Using a national site database, and 25 m resolution digital elevation model, he estimated that at least 9,430 known sites, or 14% of all known sites, were within 5 m of current sea level, with many plotting at or below sea level already.
Erosion from SLR is projected to impact 1,954 known coastal archaeological sites in New Zealand (Aotearoa). Image adapted from Figs. 1 and 5 in Jones et al. (85).
Long-term planning around SLR requires large-scale, rich geospatial data on the location of known sites as well as an understanding of the natural environments in different coastlines and how these are likely to change in the coming years [e.g. (67, 86, 87)]. In New Zealand's (Aotearoa) 15,000 km long coastline, Jones et al. (85) not only presented an improved snapshot of which parts of the coast will be impacted more than others, but also highlighted the cultural value of certain types of sites (burials) over other kinds of sites. They suggested that 22% of all coastal archaeological sites are situated in low-lying landscapes where the risks of flooding and erosion are greatest (85).
Peru: El Niño Southern Oscillation climate variability and human-driven threats
In Peru, archaeological sites have long been seen as inseparable from the natural landscape. In fact, the Peruvian term for archaeological site, huaca, derives from the Quechua word wak’a, which ethnohistorically referred to the spiritual energies housed within archaeological ruins and prominent landscape features such as waterfalls and mountains [see (88)]. Here, Indigenous biocultural heritage plays an integral part in the country's national identity, and tourism accounts for nearly four percent of the country's Gross Domestic Product (89). As such, risks to archaeological sites on the coast and elsewhere in the country are of immediate concern for Peru's livelihood. The arid Andean coast provides ideal conditions for archaeological preservation and is an incredibly large repository of Indigenous settlement of the Americas. The largest impacts to archaeological sites in coastal Peru are urban sprawl, industrial agriculture and irrigation expansion, and El Niño Southern Oscillation (ENSO) climate variability.
Peru has seen a significant coastal population increase over the past 50 years, leading to population pressures around the periphery of urban coastal centers where unregulated sprawl has collided with Peru's archaeological heritage (90). Major ancient centers such as the Chimú Empire's capital of Chan Chan, a UNESCO World Heritage Site currently on the List of World Heritage in Danger (91), are at risk. A Landsat study within Peru's Moche Valley revealed that out of 477 archaeological sites documented 50 years ago, only 113 remain (92). Similar examples are found in nearby valleys like the Chicama Valley (Fig. 5), where significant expansion of municipality and sugarcane monoculture over the past decade are observed at the coast proximal to the El Brujo archaeological complex. Occupation of El Brujo extends to 12,500 BCE and early inhabitants of the continent (93). The entire adjacent coastline is being rapidly modified by people today (Fig. 5) and hosts archeological archives of the livelihoods of these early people and their adaptations to a changing environment [e.g. (94)].
Satellite images from (A) December 2023 and (B) November 2013 document the expansion of sugarcane monocultural agriculture (green outline) and municipal infrastructure (blue outline) adjacent to the El Brujo archaeological complex of the Chicama Valley, Peru. Images obtained from Google Earth.
Agriculture and urban expansion are by far the two biggest contributors to site destruction here. Many of Peru's coastal sites are located on river valley margins, which are now located in arable zones due to recent irrigation advances aimed at corporate export agriculture, which endangers archaeological heritage as well as local land rights and water sustainability (95). Housing and agricultural solutions that focus on biocultural sustainability could help to alleviate pressures on archaeological sites, as well as to prevent further environmental degradation within urban peripheries and major agricultural zones.
Like the Mississippi River and Rhine-Meuse delta examples presented here, many valleys of coastal Peru are shaped and fed by relatively large rivers which have supported ancient and present communities. Yet, unlike the U.S. and Dutch examples, Peru has a relatively stable active margin coastline with hard substrate and only a thin veneer of Holocene sediment. It therefore has lower vulnerability to inundation than regions like the Rhine-Meuse and Mississippi River deltas where relative SLR is enhanced by sediment compaction and land surface subsidence. Unique to the other examples, a large unknown for coastal Peru is how climate change will impact ENSO intensity and variability in the future. Rainfall associated with major ENSO events rapidly erodes and washes away coastal archaeological sites, including those made of mud brick architecture and especially stone geoglyphs (96) note that flooding associated with increased extreme weather pose particular risk to geoglyphs such as the world-renowned Nazca lines in southern Peru and Chile (96). Significant rainfall associated with ENSO is difficult to predict (97), and further analyses of archaeological paleoclimate records could provide valuable data to better understand climate change associated with ENSO behavior (98).
Regulatory frameworks for coastal biocultural resource protection
SLR, rapid-onset hurricanes, long-term erosion, and subsidence present the primary threats to biocultural archaeological resources along the U.S. Gulf and Atlantic Coasts and Oceania. Flooding, salinization, and drought are the primary impacts in the Netherlands, while coastal Peruvian biocultural archaeological resources are mostly impacted by unregulated development, industrialized agriculture/irrigation, and episodic climatic flooding brought by ENSO events. In these diverse regions, regulatory and policy frameworks do not effectively manage meaningful actions to mitigate the effects of climate change and development to leverage enhanced coastal environmental protection measures. The examples herein demonstrate an urgent need for cohesive management strategies, legislation, and funding to protect coastal archaeological and biocultural resources from the combined impacts highlighted in this study. Long-term research projects in different parts of Europe, including SCAPE Scotland (99) and intensive work in along the coasts of Western France (100, 101), show how successful such approaches can be. Part of this success is grounded in the important role of local community groups in heritage management.
Returning to the U.S. Gulf Coast, we scrutinize current U.S. regulatory frameworks, financial resources and whether they are fully realized for site protection. Within the United States, the 2021 Infrastructure Investment and Jobs Act promotes archaeological research through construction projects and federal land management. It addresses climate change via rail upgrades, electric vehicle infrastructure, ecological initiatives, clean water access, pollution mitigation, and clean energy investments (102). However, it lacks a direct response to SLR impacts on coastal archaeological sites. The RESTORE Act was established in 2012 as a response to the BP Deepwater Horizon rig explosion, which released approximately 4.9 million gallons of oil into the Gulf of Mexico, and which impacted over 1,000 miles of Gulf Coast shoreline, the entirety of which is blanketed in Indigenous and historically important archaeological sites and biocultural landscapes. Approximately $16.6 billion from the act and subsequent Clean Water Act fines made their way to various Gulf Coast state governments, federal agencies, and nongovernmental organizations, to be used for restoration, recovery, and/or research programming (42, 103, 104). Of hundreds of projects supported by RESTORE Act funding, few, if any, have involved restoring and preserving archaeological landscapes that are inherently constituent elements of coastal ecosystems (Fig. 6). While funds have been used for many different marsh and habitat rehabilitation programs, for species management, and on water quality issues, critical issues still remain. We contend that (i) archaeological sites must be incorporated into a unified biocultural resource management program and (ii) spatial and temporal scales of restoration must include long-term anthropogenic influence to environments (105).
Flowchart designating select restoration funding opportunities for the U.S. Gulf Coast that could be better leveraged for cultural resource protection. Legend: National Fish and Wildlife Foundation (NFWF), Coastal Protection and Restoration Agency (CPRA), National Oceanic and Atmospheric Administration (NOAA), National Academy of Sciences-Gulf Research Program (NAS-GRP), Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA), National Science Foundation (NSF), Human, Disasters, and the Built Environment (HDBE), National Endowment for the Humanities.
Synthesis and recommendations
Our analysis of select global coasts demonstrates that severe impacts to archaeological sites are occurring now and many sites are at risk of future loss. Despite decades-old calls to address this issue, little action has been taken. Rising oceans threaten to inundate or erode entire landscapes of cultural and natural resources. Drought risks are increasing site loss in some low-lying environments. In others, rapid development and industrialization threaten natural and cultural heritage.
This problem is globally relevant, particularly in low-lying regions where studies advocate holistic approaches to climate risk mitigation (106–110). Based on a global selection of regionally focused analyses, we demonstrate the urgent need for policies integrating coastal ecosystem management with archaeological and historical resource preservation. Furthermore, we propose using participatory methods, Indigenous Traditional Ecological Knowledge (ITEK), and cultural-ecosystem services (CES) approaches to enhance resilience and align preservation with local and global heritage priorities. Local, state, federal, and global policies should be aligned to explicitly protect and promote archaeological sites as part of environmental restoration goals.
The Millennium Ecosystem Assessment and Intergovernmental Panel on Climate Change reports outline climate crisis management practices (111, 112). One approach is CES (111), utilized for ecological restoration planning in the Eastern Cascades of Washington State. Using participatory mapping with local and Indigenous collaborators, Helmer et al. (111) found some restoration practices positively impact cultural ecosystems, while others may negatively affect resources overlooked by typical surveys. The CES approach views ecosystems as coupled natural-cultural systems, identifying valuable landscapes that might be missed by current policies and providing a method of identifying synergies and trade-offs among cultural and natural impacts of restoration projects (Fig. 7). Identifying linked cultural-natural components of landscapes require first a theoretical leap in which nature is conceived to also be the product of human intervention, and that these places of natural character have been influenced by human efforts since they were first occupied. Participatory geographical information systems (PGIS) methods, used globally, involve stakeholder communities in defining culturally significant areas (113–120). The ecosystem services approach balances cultural and natural systems management by measuring benefits and trade-offs of an action, offering a comprehensive framework that could be utilized in coastal landscape protection, despite its anthropocentric focus.
Schematic diagram illustrating how indigenous infrastructure like earthen and shell mounds, ITEK, and traditional cultural modification to the landscape buffer hazard sensitivity. Anthropogenically enhanced soils and Indigenous, human-made mounds, middens, and monuments positively influence the net biodiversity of coastal marsh, thereby creating a coupled natural-cultural system. We call this phenomenon CER. In the figure, solid lines indicate direct influence and impact, and the width of the lines indicates a relative scale of impact. Dashed lines indicate buffered sensitivity to natural hazards and human-generated threats. The left side of the figure demonstrates how natural hazards and human-generated threats are mitigated by CER through feedback in an anthropogenic system. No such buffering is present in natural deltaic marshes.
Another opportunity for increased integration among natural and cultural land management initiatives comes from utilizing ITEK approaches. In 2021, President Biden issued an Executive Order mandating the incorporation of ITEK into Federal Decision Making. Federal agencies and affiliated Tribes are now devising operation plans for implementing ITEK into land management across the nation. For instance, the Great Lakes Indian Fish and Wildlife Commission recently put forth a “Tribal Climate Adaptation Menu” that provides guidance to federal agencies and others for how to integrate Tribal perspectives into land management decision making (121). As mentioned previously, nearly all Indigenous worldviews see the natural and cultural worlds as one inseparable entity that we are all a part of, including humans, plants, animals, and the earth. ITEK will be key to effective coastal management and resilience and should serve as a guiding principle in breaking down natural-cultural barriers inherent in Western science [e.g. (122)].
As one of the largest environmental fines ever committed to coastal restoration due to impacts from the BP oil spill, the RESTORE Act provides lessons that can be implemented worldwide. Current funding opportunities under the RESTORE Act privilege restoration activities targeting landscapes that are fundamentally both natural and cultural; however, funding activities only allow for restoration and study of ecological components, not archaeological or historical sites, nor cultural landscapes that are part and parcel of these natural landscapes. While these projects fulfill their regulatory compliance requirements to consider project impacts on cultural resources, which they are legally required to do, they do not integrate cultural resources or archaeological sites as part of biocultural landscapes and project goals from the outset. We propose moving beyond regulatory requirements in favor of a systems approach that brings humans and the past back into the overall landscape resilience framework. Furthermore, we suggest that professional archaeological organizations, like the Society for American Archaeology, among others, should take a more active role in lobbying policymakers to ensure that Indigenous archaeological and cultural heritage is better represented in legislative and executive actions.
In our analysis of RESTORE Act funding opportunities (Fig. 6; Supplemental Information S1 and Table S2), it is clear that environmental scientists and ecologists have ample opportunities to support research and restoration efforts through various funding mechanisms. Whether obtained directly through a federal agency or directed through state agencies and local nonprofit agencies, scientists working around the Gulf of Mexico have access to hundreds of millions of dollars in research and restoration. Additionally, we suggest that much of the RESTORE Act and similar large restoration funding mechanisms could benefit from recent insights uncovered from PGIS and CES data about coupled natural-cultural systems and the relationship between sites of cultural heritage and natural ecosystems. In particular, what participatory mapping demonstrates is that stakeholder communities identify and map heritage and cultural landscapes differently than federal guidelines dictate and in ways that accord better with global heritage protections (111, 123).
Many of the archaeological sites included in the examples presented here are in coastal ecosystems utilized for multiple services: fishing, hunting, sightseeing, birding, beach going, swimming, snorkeling and diving, resource gathering, and oil/gas extraction. Within these same ecosystem services are sites of cultural heritage ranging from the first Indigenous inhabitants to historic fortification to early industrial fishing and harvesting sites and landscapes. In all these places, various stakeholder communities have connections to the past histories of these places, whether they were mid-20th century fishing camps of international migrants, clandestine villages of escaped enslaved Africans looking to claim their freedom, heavily defended brick forts built to support various colonial armies, and/or Indigenous earthen and shell mounds and middens. Participatory GIS mapping of interested stakeholders, Indigenous groups, and/or descendant communities might map meaning onto certain landscapes and employ memory, oral history, and experience toward valuing and preserving places not easily categorized under federal and/or state regulatory statutes. PGIS can effectively integrate both cultural and natural categories and holistically consider natural-cultural systems because users (stakeholders) are not constrained by policy and/or guidelines, but rather by their own perspectives of what they value in the environment.
Current policy and community guidelines are particularly scarce in tribal communities and are nearly absent for any type of community as they relate to integration of historic or cultural preservation and hazard planning (124, 125). To be more efficient and impactful to the community, this integration particularly calls for greater public participation in planning processes, yet engagement of socially vulnerable populations remains an ongoing challenge to hazard planning and preservation research (126). This study reveals the need for more localized, context-sensitive planning efforts to address historic or cultural preservation. The policy gaps revealed by this study offer important opportunities for improvement, allowing planners to ask critical policy questions about local priorities to address cultural preservation in a changing climate (127). This study offers a new approach for planning practitioners and decision-makers to locate the areas of cultural importance and awareness as part of the broader biocultural landscape lens, helping align local cultural preservation priorities reduce archaeological sites and Indigenous heritage from the climate risk effectively and equitably.
Federal, state, and international programs that provide grant funding to address and investigate SLR (and related impacts) to archaeological sites in coastal zones need to be catalyzed in order to conserve, repair, and salvage these quickly deteriorating landscapes. Large field and laboratory crews need to be quickly established to salvage archaeological data and plan restoration measures when needed, especially where erosion, land loss, and subsidence are predicted to occur rapidly. We need a “New Deal” for American and World Archaeology that dramatically funnels and focuses scholarship, students, and Indigenous communities towards collaboratively working to save our collective archaeological and biocultural patrimony through the full integration of natural and cultural resource management systems. It is only through these kinds of initiatives that we will be able to stem the rising tide of archaeological site and Indigenous heritage loss.
Acknowledgments
The authors recognize contributions, inputs, and efforts of the Gulf Resilience Hub and from their community members. They extend gratitude to the Louisiana Division of Archaeology and the Florida State Historic Preservation Office for their assistance with site data.
Supplementary Material
Supplementary material is available at PNAS Nexus online.
Funding
This work was supported by the National Science Foundation Coastlines and People Hubs for Research and Broadening Participation (CoPe), Award #2052930.
Author Contributions
J.M.M.—Conceptualization, Design, Authorship, Editing. E.L.C.—Authorship, Editing. E.H.—Background Research. M.H.—Authorship, Editing. M.D.M.—Authorship. R.v.B.—Authorship. H.W.—Authorship. S.Y.—Authorship.
Data Availability
The data that support the funding policy analysis can be found in Supplemental Information 1. Additional resources on Restore Act funding can be found online (https://home.treasury.gov/policy-issues/financial-markets-financial-institutions-and-fiscal-service/restore-act/about-treasurys-restore-act-programs). NOAA SLR data are openly accessible at the Digital Coast website (https://coast.noaa.gov/slrdata/). Site location data used for the archaeological site impact analysis are federally protected information and not available publicly. Data tables outlining SLR site impact analysis can be found in Supplemental Information 1. Interested parties can contact local state historic preservation offices directly to inquire about gaining access to site locations. The Coastal State Site Data for Sea Level Rise Modeling employed by David Anderson and his team (128) can be accessed at https://doi.org/10.6078/M7ST7MRR—these data have been downregulated and anonymized in order to protect actual site locations.
References
Author notes
Competing Interest: The authors declare that they have no competing interests.
