Early to Middle Holocene Estuarine Shellfish Collecting on the Islands and Mainland Coast of the Santa Barbara Channel, California, USA

Torben C Rick

doi:10.5334/oq.86

Abstract

Terminal Pleistocene to Middle Holocene sea level rise resulted in a number of changes to coastal ecosystems around the world, providing new challenges and opportunities for coastal peoples. In California, glacial to interglacial sea level rise resulted in some reductions in rocky shore kelp forests, but it also resulted in the formation of estuaries. Estuaries were important for terminal Pleistocene peoples in the Santa Barbara Channel region (SBC), a pattern that persisted through the Early to Middle Holocene, and sometimes later. While paleoestuaries appear to have been relatively common along the SBC mainland coast, they were rare to absent on the Channel Islands. The Abalone Rocks Paleoestuary on Santa Rosa Island is the only well documented island estuary. However, questions remain about the size and productivity of this estuary and its importance for human subsistence and settlement relative to the more extensive mainland estuaries. Faunal data from two previously unreported site components and synthesis of shellfish data from other Abalone Rocks sites and similarly aged sites near mainland estuaries illustrate the importance of SBC mainland versus island estuaries. Estuarine shellfish were considerably more abundant at most Early and Middle Holocene mainland sites, with the Abalone Rocks Paleoestuary largely supplementary to rocky shore habitats. At island estuary sites, taxonomic richness was fairly consistent during the Early to Middle Holocene, although diversity and evenness decline slightly through time, with estuarine shellfish largely disappearing from island assemblages prior to 5000 years ago. These data demonstrate the power of archaeological research to evaluate the relationships between past environmental change and human behavior.

Highlights

Estuaries have long been important habitats for coastal peoples around the world, with the diversity of estuarine habitats and organisms supplying people with important food and other resources
Estuaries continued to be of importance to human subsistence economies through historic times in parts of California, but they appear to Department of Anthropology, National Museum of Natural History, Smithsonian Institution, Washington, DC, US rickt@si.edu have been important during the Early and Middle Holocene when sea level rise resulted in the formation of a series of estuaries, including in the Santa Barbara Channel Region (SBC) (Erlandson 1985, 1994, 1997; Glassow 1997, 2020a; Reeder-Myers 2014a)
Radiocarbon dating of archaeological sites on eastern Santa Rosa Island demonstrates that Abalone Rocks was a focus of human settlement and subsistence between about 8000–5000 years ago (Rick 2009), which roughly corresponds with the timing of estuarine conditions documented in paleoecological cores (Anderson et al 2010; Cole & Liu 1994)

Summary

Introduction

Estuaries have long been important habitats for coastal peoples around the world, with the diversity of estuarine habitats and organisms supplying people with important food and other resources. In California and elsewhere on the North American Pacific Coast, estuarine resources were important in early coastal economies and were part of a broadening of human use of a range of coastal habitats from the terminal Pleistocene through the Middle Holocene (Erlandson 1994; Erlandson et al 2019; Graham et al 2003; Jones & Hadick 2016; Jones et al 2019; Masters & Aiello 2007). Despite a few studies exploring the importance of estuarine habitats on Santa Rosa Island during the terminal Pleistocene to Middle Holocene, there has been limited research comparing human use of Channel Island estuaries to the estuarine systems on

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