Clam gardens

By Skye Augustine, Melissa Poe, Anne Salomon, and Dana Lepofsky

Ancestral Connections & Geographic Extent Temporal Extent Biophysical Manipulations Target Species Ceremony & Stewardship Current Status

Oral historical, ethnographic, and archaeological evidence reflect a wide distribution of clam garden features throughout the Northwest Coast of North America, from Alaska, through British Columbia, to Washington (Williams 2006, Hul’qumi’num Treaty Group 2011, Lepofsky et al. 2015, Hul’q’umi’num’-Gulf Islands National Park Reserve Committee 2016, Moss and Wellman 2017, Olsen 2019, Stern 1934). While their use is specifically mentioned in the ethnographic records of several coastal Indigenous Peoples, including the Tlingit, Haida, Heiltsuk, Kwakwaka’wakw, Nuu-chah-nulth, and Northern, Central, and Southern Coast Salish, archaeological records demonstrates that gaps in ethnographies reflect gaps in recording rather than regional discontinuities in this ancestral practice. A combination of changes including relative sea levels, contemporary intertidal industrial development, and restricted access to privately owned intertidal zones has hampered efforts to confirm the likely full extent of ancient clam gardens. Our collective knowledge of these intertidal features suggests that their occurrence and density along shorelines, their morphological structure, and the seafood species targeted, and governance systems vary with cultures and communities and likely has done so throughout time. 

Indigenous knowledge holders recount that clam gardens have been maintained and cared for “since the beginning of time” (Deur et al. 2015). Determining the age of specific rock features requires using radiocarbon or optical luminescence dating techniques to date biological organisms or sediments trapped by the building of the rock wall or the in-filling of the terrace (Neudorf et al. 2017, Smith et al. 2019). Based on these techniques, clam gardens have been dated to at least 3500 years ago (Smith et al. 2019). In areas where shorelines are known to have been higher or lower in the past due to changes in sea level, the position of the rock wall in today’s intertidal can also be used to infer the age of the wall construction (Smith et al. 2019). 

The focus of scientific dating has been mostly on the timing of initial terrace wall construction. However, oral traditions and the archaeological record demonstrate that clam gardens have been modified and refurbished throughout the millennia. Luminescence dating indicates that terrace infilling was slow (Neudorf et al. 2017). This supports Indigenous knowledge that garden walls were built by generations of people rolling rocks onto the terrace wall and keeping the beach clean (Hul’qumi’num Treaty Group 2011, Deur et al. 2015). In response to ever-changing local sea levels, people modified walls, built entirely new walls at different tidal heights on the same beach, or abandoned gardens for new locations. 

Intertidal clam gardens exist where the land meets the sea, as part of a continuum of nearshore ecosystems that were tended along the coast (Jackley et al. 2016, Mathews and Turner 2017). Tending included a wide range of practices including rock wall construction and maintenance, tending and tilling of sediment, addition of shell hash and gravel, selective clam harvesting, juvenile clam transplanting, and predator and debris removal (Hul’qumi’numTreatyGroup 2011, Lepofsky and Caldwell 2013, Deur et al. 2015, Lepofsky et al. 2015, Olsen 2019). 

Clam gardens typically consist of a rock wall at the low tide line that traps sediment and reduces the slope of a beach. Mechanistically, the rock walls reduce the average height of the upper intertidal and increase the average tidal height of the lower intertidal, maximizing the intertidal habitat within the ideal tidal height for target clam species (Groesbeck et al. 2014, Jackley et al. 2016) and allow more clamming beach to be exposed during moderate tides (Lepofsky et al. 2021). Clam gardens are designed to take advantage of natural geomorphic and ecological processes, and as such, vary in their specific landscape modifications. Such modifications range in extent and kind, depending on the site. In general, there are three categories of where and how wall construction occurred  (on previously existing clam beaches, on bedrock, on steep eroding slopes). The number and kind of gardens influenced the extent and nature of nearshore modification. In some regions, clam gardens were built wherever there was available shoreline, amounting to as much as a 33% increase in clam habitat (Lepofsky et al. 2021).  

The building of rock walls and the formation of terraces create favourable habitat for a range of culturally valued species. The rock walls themselves promote water retention, effectively moderating temperature extremes, and promote water flow – maximizing the delivery of nutrients to clams (Salter 2018).  Palaeoecological and archaeological records indicate that building clam gardens created habitat at least as good as the best natural habitat (Toniello et al. 2019). Furthermore, they also indicate that clam gardens today – while more productive than unwalled beaches (Groesbeck et al. 2014, Jackley et al. 2016) – are less productive than the clam gardens of the pre-industrial past. This is likely because of a combination of recent modifications to the foreshore as well as the dramatic decline in traditional marine management systems and active beach tending as a result of a range of colonial processes (Toniello et al. 2019). Today, in addition to clam habitat, in some regions, clam garden walls also support a nearshore kelp forest and promote the growth of a variety of macroalgal and macroinvertebrate food species that were also cared for and harvested (Hul’qumi’num Treaty Group 2011, Hul’q’umi’num’-Gulf Islands National Park Reserve Committee 2016, Olsen 2019). 

Tending practices contribute to optimizing sediment quality, maximizing clam growth, and increasing the success of clam recruitment. The sediment in the gardens was managed by adding shell, removing small rocks from the beach, and tilling using a specialized digging stick. The knowledge encompassed within these practices was passed down intergenerationally, while working together to care for the beaches, and through songs and stories (Deur et al. 2015). 

Our knowledge of the target species is based on oral traditions, songs, ethnographic observations, the archaeological record, and recent conversations with ecological knowledge holders.  Together, these diverse sources and systems of knowledge and data demonstrate that by creating and caring for the intertidal ecosystem, Indigenous Peoples increased their access to a range of culturally valued species. Culturally important species cultivated in clam gardens include utter clams (Saxidomus gigantea), littleneck clams (Leukoma staminea), horse clams (Tresus capax), and cockles (Clinocardium nuttallii), red rock crabs (Cancer productus), whelks (Nucella lamellosa, Ceratostomafoliatum), sea cucumbers (Cucumaria miniata, Apostichopus californicus), sea urchins (Strongylocentrotus droebachiensis), octopus (Enteroctopus dofleini), chitons (Mopalia spp.), and seaweeds (Ulva spp. Pyropia spp.). Even species of salmon were caught owing to clam gardens.

Conversations with Hul’q’umi’num’ and W̱SÁNEĆ Elders describe different species and harvesting practices for specific clam gardens across the Salish Sea. In fact, harvest practices are beautifully nuanced to the conditions and quality of each clam garden. Many people may be surprised to know that Indigenous people visited some clam gardens in the Salish Sea to harvest salmon. For example, Coast Salish Elders talk of harvesting salmon standing from the rock wall of clam gardens (pers comm to Augustine 2020). There are several walled clam beaches in British Columbia that Elders describe as rock walls that guide salmon home to rivers, recalling spearing these salmon from the wall while they swam past.

Clams are harvested by Indigenous people at various times of the year. Today, some people describe that ‘clams bring Christmas”, providing a welcome source of fresh seafood and income in time for the holidays. Traditionally, clams were prepared and eaten fire roasted on the beach, in clam and seafood chowder, and in the past, were preserved in the form of barbequed clam necklaces. Clam necklace preparation required a day or more to fully dry the clams. Once strung onto a cedar root to make a necklace, they acted as a readily available source of protein (pers comm Augustine 2020).

The protein rich necklaces produced from gardens were prized foods often brought on voyages as a quick food, used as currency for trade, and as gifts in potlatch ceremonies. Shellfish historically grown in clam gardens fed communities far from the coast and beyond the headwaters of massive rivers and trade routes, connecting coastal Nations with those in alpine and prairie regions. Shellfish were traded for materials such as obsidian, mountain goat wool, and rattlesnake venom.

Today most clam gardens on the northwest coast of North America are within the jurisdiction of provincial or state governments, with exceptions in British Columbia, Canada being located on Indian Reserve lands or within Federal jurisdiction in National Parks or Park Reserves. In Washington State, USA, clam beaches fall within a complex matrix of ownership that includes treaty-reserved usual and accustomed areas, tribal reservation tidelands, managed public beaches, and private holdings.  

Throughout the Northwest coast, there is a renewed focus on revitalizing clam gardens as part of a larger movement towards Indigenous governance reassertion, cultural reconnections, and food sovereignty. There are several efforts underway to restore and reawaken intertidal clam gardens by a number of Indigenous groups across the Northwest Coast of North America. For example, Hul’q’umi’num’ & W̱SÁNEĆ Coast Salish communities are leading the first experimental restoration of clam gardens in the Southern Gulf Islands of British Columbia and are working with Parks Canada to do so (Hul’qumi’num Treaty Group 2011, Olsen 2019). The Swinomish Indian Tribal Community in Washington State is leading the first initial clam garden construction in modern day as part of the Tribe’s climate change adaptation program. Lastly, Indigenous individuals in places across the Pacific Northwest continue to roll rocks to the low tide walls, tend beaches, and harvest clams from clam gardens.

More Information

 www.clamgarden.com 

References

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Hul'qumi'num Treaty Group. 2011. Gulf Island National Park Reserve - Hul’qumi’num Treaty Group shellfish traditional knowledge research project. Sidney, BC, Canada.

Hul’q’umi’num’- Gulf Islands National Park Reserve Committee. 2016. Stutul’na’mut report: caring for our beaches. Report prepared for Parks Canada. On file in Duncan, BC and Sidney, BC. 

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