Indigenous people farmed oysters sustainably for 5000 years

A new archaeological study has unearthed evidence Indigenous people in Australia and North America sustainably managed and consumed oysters for thousands of years.

Oysters are a popular food source for many communities around the world, yet populations of wild oyster species have crashed in regions of both Australia and the United States since European colonisation. It’s estimated that up to 85% of 19th century oyster reef areas have been lost, through a combination of commercial over-exploitation, habitat changes, and the spread of diseases and introduced species.

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Now, a large international team of archaeologists and anthropologists has compiled evidence stretching back thousands of years to understand how these resources were managed before European colonisation. The team was led by Torben Rick of the Smithsonian Museum of Natural History and Leslie Reeder-Myers of Temple University, both in the US, and included members of some First Nations groups from the areas studied.

“Oyster harvesting didn’t start 500 years ago with the arrival of Europeans,” explains study co-author Bonnie Newsom, an anthropologist at the University of Maine, US, and citizen of the Penobscot Indian Nation. “Indigenous peoples had a relationship with and understood this species well enough to use it as part of their subsistence and cultural practices.”

Archaeologists excavating a midden containing the remains of oysters
A dense shell midden deposit spanning the past 1,000 years as exposed during excavation at a Tseshaht First Nation village in the Pacific Northwest of the US. Credit: Iain McKechnie.

Oyster detectives

Much of the team’s data came from archaeological formations called middens. Middens are artificial deposits usually containing shells, ash or charcoal, bones and other artefacts. They can reveal information about the diets and sometimes cultural activities of people who lived in the past.

By using data about the oyster shells found in middens and other archaeological sites, the researchers were able to shed light on how oysters were harvested and eaten. Some of the oldest oyster middens in North America were dated as more than 6000 years old. In Australia, oyster shells harvested at Saint Helena Island near Brisbane are estimated to date back more than 1000 years.

The data indicate that Indigenous people were consuming oysters in large numbers. An island called Mound Key off the Gulf Coast of Florida in the US was estimated to contain the shells of 18.6 billion oysters, and a second site in Florida holds the remains of about 2.1 billion oysters.

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“We knew there were big sites in the southern US, but when we started to calculate just how many oysters were in these sites, we were astonished,” says Rick.

The comparatively modest Saint Helena Island site in Australia was estimated to contain about 50 million oyster shells.

Looking at the size of the oyster shells at a given site can give an indication of how sustainable the oyster harvest was. If the shells get smaller over time, that suggests the oysters are being over-exploited. However, little evidence of such a pattern has been found at Indigenous oyster fisheries. 

The research team combined the archaeological data with records of past sea levels and oyster catches, and historical accounts of oyster use by Indigenous communities.

A very large midden containing oysters covered in grass with wooden stairs built to the top and a person standing in front
Crystal River site in Florida, US, with massive shell mounds, dominated by oysters, pictured here during archaeological mapping and showing the modern staircase and platform built on top of one of the mounds. Credit: Victor Thompson.

Learning from the past

The authors say the findings have important lessons for the present day. The paper emphasises that, rather than a story of pristine wild oyster populations being overwhelmed by human exploitation, the evidence tells a story of Indigenous knowledge and practices that allowed people to actively nurture and sustainably manage food resources over thousands of years.

“These systems have a ton of potential and huge quantities of oysters can be sustainably harvested over long time periods if the ecosystem is healthy,” explains Reeder-Myers.

Newsom adds: “Indigenous peoples have a lot to offer in terms of how to engage with this natural resource in ways that are sustainable.”

For Rick, the results highlight how colonialism and environmental destruction go hand in hand – and need to be tackled together.

Read more: Indigenous stewardship linked to biodiversity

“Conservation today can’t just be seen as a biological question and can’t just be about undoing the environmental damage we’ve done in the modern era,” he says. “Instead, global conservation efforts should be coupled with undoing the legacies of colonialism which brought about the attempted erasure and displacement of Indigenous people all over the world.”

He hopes the study will spark a wider dialogue among conservationists about respect for Indigenous knowledge, which is based on millennia of ecosystem stewardship, and inclusion of Indigenous communities in environmental management decisions.

“This broadening of perspectives can enhance biological conservation and help restore connections between Indigenous peoples and their ancestral homelands,” he concludes.

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