Ancestral sea gardens supported human settlements for at least 3,800 years on the Northwest Coast of North America (original) (raw)
Related papers
Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating. This study demonstrates the efficacy of dating clam garden wall construction using optical dating, and uses optical ages to determine how sedimentation rates in the intertidal zone are affected by clam garden construction. Clam gardens are rock-walled, intertidal terraces that were constructed and maintained by coastal First Nation peoples to increase bivalve habitat and productivity. These features are evidence of ancient shellfish mariculture on the Pacific Northwest and, based on radiocarbon dating, date to at least the late Holocene. Optical dating exploits the luminescence signals of quartz or feldspar minerals to determine the last time the minerals were exposed to sunlight (i.e., their burial age), and thus does not require the presence of organic material. Optical ages were obtained from three clam garden sites on northern Quadra Island, British Columbia, and their reliability was assessed by comparing them to radiocarbon ages derived from shells underneath the clam garden walls, as well as below the terrace sediments. Our optical and radiocarbon ages suggest that construction of these clam garden walls commenced between ~1000 and ~1700 years ago, and our optical ages suggest that construction of the walls was likely incremental and increased sedimentation rates in the intertidal zone by up to fourfold. Results of this study show that when site characteristics are not amenable to radiocarbon dating, optical dating may be the only viable geochronometer. Furthermore, dating rock-walled marine management features and their geomorphic impact can lead to significant advances in our understanding of the intimate relationships that Indigenous peoples worldwide developed with their seascapes.
PLOS ONE, 2017
Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating. This study demonstrates the efficacy of dating clam garden wall construction using optical dating, and uses optical ages to determine how sedimentation rates in the intertidal zone are affected by clam garden construction. Clam gardens are rock-walled, intertidal terraces that were constructed and maintained by coastal First Nation peoples to increase bivalve habitat and productivity. These features are evidence of ancient shellfish mariculture on the Pacific Northwest and, based on radiocarbon dating, date to at least the late Holocene. Optical dating exploits the luminescence signals of quartz or feldspar minerals to determine the last time the minerals were exposed to sunlight (i.e., their burial age), and thus does not require the presence of organic material. Optical ages were obtained from three clam garden sites on northern Quadra Island, British Columbia, and their reliability was assessed by comparing them to radiocarbon ages derived from shells underneath the clam garden walls, as well as below the terrace sediments. Our optical and radiocarbon ages suggest that construction of these clam garden walls commenced between~1000 and~1700 years ago, and our optical ages suggest that construction of the walls was likely incremental and increased sedimentation rates in the intertidal zone by up to fourfold. Results of this study show that when site characteristics are not amenable to radiocarbon dating, optical dating may be the only viable geochronometer. Furthermore, dating rock-walled marine management features and their geomorphic impact can lead to significant advances in our understanding of the intimate relationships that Indigenous peoples worldwide developed with their seascapes.
11,000 Years of Human-Clam Relationships on Quadra Island, Salish Sea, British Columbia
2017
The historical ecological approach provides unique insights into the relationship between humans and clams throughout the Holocene. Combing archaeological and palaeo-fossil records provides a time depth of clam history both with and in the absence of intensive human predation. These results show that butter clam (Saxidomus gigantea) growth was naturally improving from the early-to-mid Holocene and that humans took advantage of the expanding clam resources. Clam garden construction around 2,000 BP promoted the sustainability of clams, and despite increased harvesting pressure there is no evidence for resource depression. Since European contact, decline of traditional management practices and increases in industrial activities have resulted in reduced clam growth rates. Growth rates of living clams reflect the stunted growth of post-glacial early Holocene clams, making them the slowest growing clams in the past ~10,000 years. Deeper-time baselines more accurately represent clam population variability throughout time and are useful for modern coastal resource management.
Ancient Anthropogenic Clam Gardens of the Northwest Coast Expand Clam Habitat
Ecosystems, 2020
Clam gardens are ancient mariculture features developed by Indigenous Peoples of the Northwest Coast of North America that create shallow sloping intertidal shelves where clam productivity is enhanced. We quantify the area of clam habitat created by constructing rock-walled clam gardens terraces in northern Quadra Island, British Columbia, Canada. We combined modelling, highresolution mapping, beach sampling, and a comprehensive survey of the shoreline to document the location and areal extent of clam habitat in clam gardens today. We divided our analysis into three classes of clam gardens, which differ in substrate and thus the amount of clam habitat created. We found that Indigenous People built clam garden walls on 35% of the shoreline and that about 112,979 m 2 of flat beach terrace were created by clam garden construction. Collectively, the three classes of clam gardens increased clam habitat area between 26 and 36%. About 35% of the area of clam habitat in clam gardens was constructed de novo on bedrock shelves and rocky slopes where no clam habitat existed previously. Furthermore, about 12.0% of clam gardens are smaller than 30 m 2 , reflecting the effort put into creating enhanced food production wherever possible. Our analysis demonstrates that clam management in the form of clam gardens was extensive prior to colonization and that these features still have a significant impact on today's intertidal ecosystems. Clam habitat expansion facilitated by clam garden construction encouraged a sustainable and abundant food source in the past and could do so again in today's changing environmental conditions.
PNAS, 2019
Historical ecology can provide insights into the long-term and complex relationships between humans and culturally important species and ecosystems, thereby extending baselines for modern management. We bring together paleoecological, archaeological, and modern clam records to explore the relationship between humans and butter clams (Saxidomus gigantea) throughout the Holocene in the northern Salish Sea of British Columbia, Canada. We compare butter clam size and growth patterns from different temporal, environmental, and cultural contexts spanning 11,500 y to present. Butter clam size and growth were restricted in early postglacial times but increased over the next few millennia. During the early-Late Holocene, humans took increasing advantage of robust clam populations and after 3.5 ka, began constructing clam gardens (intertidal rock-walled terraces). Environmental and cultural variables, including coarse substrate, stabilized sea surface temperature, and the presence of a clam garden wall, increased clam growth throughout the Holocene. Measurements of clams collected in active clam gardens and deposited in middens suggest that clam gardens as well as other mariculture activities enhanced clam production despite increased harvesting pressure. Since Eu-ropean contact, decline of traditional management practices and increases in industrial activities are associated with reduced clam size and growth similar to those of the early postglacial clams. Deeper-time baselines that more accurately represent clam population variability and allow us to assess magnitudes of change throughout time as well as the complex interactions among humans and clams are useful for modern marine resource management. historical ecology | clam gardens | traditional resource management | Northwest Coast | paleoecology O ver the millennia, many peoples worldwide developed intimate knowledge of, and relationships with, particularly valued species of plants and animals (1). Tracking the development of these long-term human-species relationships requires temporally grounded records that provide insights into both the cultural and ecological sides of this equation. For instance, the archaeological faunal record can provide detailed information on the ecological and cultural effects of human-species interactions (2-5), whereas the paleoecological record can provide insights into species ecology in the absence of significant human intervention (6-8). Taken together, these 2 records can offer a powerful lens through which to assess coupled social-ecological systems over broad spatial and temporal scales and can help establish ecological baselines for modern management (8-12). On the Northwest Coast of North America, clams are a valued cultural species (13, 14) with widespread importance that is reflected in origin stories, rituals, language, and in the kilometers of deep and ancient shell middens that line the coastline (15, 16). Detailed archaeological and ethnographic research indicates that clams, especially butter clams (Saxidomus gigantea) and littleneck clams (Leukoma staminea), were eaten in abundance both seasonally and year round (17) and both fresh and preserved. These species were a reliable, abundant, and easily harvested source of food (13, 18) that could be tended to increase abundance by applying various traditional cultivation techniques. One such technique, the building of rock-walled intertidal terraces called "clam gardens," expanded and enhanced clam habitat and thus, clam production (14, 16, 19, 20). Complimenting the archaeological and ethnographic records, studies of subfossil and fossil bivalves on the Northwest Coast have provided significant insights into the region's paleoecol-ogy. Such data have been used for reconstructing both pre-human (21) and recent historical ecological conditions (22, 23). To our knowledge, no studies have combined both the archaeological and paleoecological marine bivalve records to fully explore the long-term relationships among humans and clams. In this paper, we investigate the historical ecology of butter clams throughout the Holocene along the northern coast of Quadra Island, Salish Sea, British Columbia (Fig. 1) through analyses of the paleoecological, archaeological, and contemporary ecological records. Together, these records encompass 11,500 y of history-a period that spans the time before extensive human settlement to Significance Climate change, habitat loss, and overharvesting are threatening coastal ecosystems worldwide. A less widely recognized threat is the decline in Indigenous mariculture practices. These practices, such as building of clam gardens, structured coastal ecosystems for millennia. Teasing out the dynamic and intertwined relationships between humans and culturally valued species, such as clams, requires long-term paleoecological and archaeological records. These records are requisite for creating meaningful management targets and for applying traditional mariculture practices, such as the tending of clam gardens, to increase the productivity and sustainability of our foods today. Documenting these interactions between humans and coastal ecosystems, such as we have done here, also counteracts the erasure of the long-term connections of Indigenous peoples to their lands and seas.
a n M c L a r e n , F a r i d R a h e m t u l l a , G i t l a ( E l r o y W h i t e ) , a n d D a r y l F e d j e 155 bc studies, no. 187, Autumn 2015 bc studies 156 territories of the Heiltsuk, Wuikinuxv, and Nuxalk nations, includes the outer coast islands and skerries to the north and south of Hakai Passage as well as the mainland shoreline on the east side of Fitz Hugh Sound ( ). Calvert and Hunter islands are two of the major outer coast islands included in the study area.
Early Environments and Archaeology of Coastal British Columbia (Mackie et al. 2011)
Mackie, Quentin, Daryl W. Fedje, Duncan McLaren, Nicole Smith and Iain McKechnie (2011). In Trekking the Shore: Changing Coastlines and the Antiquity of Coastal Settlement, edited by N. F. Bicho, J. A. Haws and L. G. Davis, pp. 51–103, Springer, New York.
Coastal British Columbia is largely a rugged fjord-land archipelago. It has not always been so – over time, the coastline has changed configuration dramatically and the fauna and flora have seen multiple successions and extirpations. Through this, for the last 11,000 RCYBP years at least, resilient people made their living from the ocean and the land, shrugging off or taking advantage of environmental change. Similarly, archaeologists have worked the nooks and crannies of the coast for decades, surveying in the dense forest and digging in the deep middens, subject to similar environmental conditions as those they study and making quiet progress in regional culture histories. In more recent years, this area has been thrust to the forefront of research into the First Peopling of the American continents. As the Clovis First model began to be questioned, alternate modes and routes for the arrival of humans were brought in from the sidelines, including the hypothesized west coast route (e.g., Fladmark 1979). Not much research had been focused on this route, perhaps as Easton (1992) suggests, because of the terrestrial mindset of many archaeologists. Perhaps also, the prospects of finding sites on the deeply drowned landscapes or in the rugged, heavily forested hinterland was prohibitively daunting and led to a pessimistic outlook on success.
Science, 1997
Marine Gares tram the continental shelf edge of British Columbia (Canada) demonstrate that sea level at the shelf edge was 153 meters below present 14,000 calendar years aga and more than 30 meters lower th an the maximum eustatic low of -120 meters. Dated artifacts, including stone tools, indicate that humans occupied this region by at least 10,200 calendar years before present (B.P.). Local sea level rose rapidly (5 centimeters per year) during the period of early human occupation as a result of eustatic sea-ievei ri se and glacio-isostatic forebulge movement. This shelf edge site was first elevated and then subsided. The exposed shelf edge was available forhuman occupation and may have served as a migration route during times of lowered sea levels between 13,500 and 9500 14C years B.P.
Research in recent decades has highlighted a complex, locally variable sea-level history across the Northwest Coast of North America. This resulted in a dynamic coastal landscape throughout the Holocene, and yields poor archaeological visibility for many periods. Early- through mid-Holocene cultural deposits are often either stranded on raised landforms some distance from current shorelines or submerged beneath contemporary sea levels. Based on a detailed reconstruction of the local sea-level history, recent research in southern Haida Gwaii has targeted such mid-Holocene deposits. In particular research at site 924T in eastern Gwaii Haanas National Park Reserve and Haida Heritage Site is revealing a persistent use of this location over at least 5000 years. A series of occupations on sequentially higher paleo-beach terraces associated with a long-term decline in sea levels in the region speak both to the importance of this location from at least the mid-Holocene to the European contact period, and also document dramatic changes in subsistence and material culture through a period that is otherwise unknown in the region. These point to a close relationship between site locations and sea level histories, and reveal long-term continuity in the use of local areas in the face of this dynamic environment.