Along the jagged coast of Maine, prehistoric shell middens mark spots where Maine Indians feasted on clams, shells and other seafood, then tossed aside the remains.

“Midden,” to archaeologists, means the waste left behind by long-gone humans. In practice, though, these ancient garbage heaps contain a treasure trove of data that can shed light on Maine’s early environment and long-ago residents. But the 2,000 known middens in Maine are seriously threatened by pressures, including rising sea levels, beach erosion and real estate development.

In order to protect the state’s cultural heritage despite those pressures, a University of Maine project is aiming to define the current extent of the middens and develop a network of citizen scientists to monitor and protect them now and in the years to come.

“The paleo information is priceless,” Alice Kelley, an associate research professor at the University of Maine Climate Change Institute, said. “The bones and the things that are there are basically our only record of what was living in the western Gulf of Maine from 4,000 years ago to the present.”

This is true because the shells in the shell middens buffer Maine’s acidic soil and allow for the preservation of soft substances such as animal bones and other artifacts. The thought of losing that archaeological record is sobering to scientists such as Kelley.

“Virtually all of them are eroding,” she said of the middens. “And the only way we’re going to know about 2,000-plus of them is by involving non-professionals. By involving local people, we hope to develop a sense of ownership and pride and involvement.”

Middens are still important to modern-day Maine Indian tribes. Chris Sockalexis, the tribal historic preservation officer for the Penobscot Nation, said the information found in them matters.

“Middens provide direct evidence and information about our ancestors and I believe we still have much to learn from them,” he said. “There are some instances where we are relearning ancient traditions used by our ancestors from distinct evidence found within middens. They are a fragile part of our landscape and should be preserved as best we can.”

It’s not the first time that middens have been imperiled. In the 19th century, many enterprising Mainers used the shell heaps as a natural resource that could be sold or used for profit. The Whaleback Shell Midden in Damariscotta, now is a state historic site, used to be more than 30 feet deep, more than 1,650 feet in length and as wide in parts as 1,650 feet. But much of it was turned into chicken feed in the late 1800s by the Massachusetts-based Damariscotta Shell and Fertilizer company.

Middens also can be endangered by looting, Kelley said. In the past, archaeologists often were reluctant to talk about middens for fear of encouraging people to dig in them and take what they find away.

“There was a time when digging in middens was really popular — Boy Scout badge popular,” she said. “But if you dig in a midden, collect arrowheads, remove them from their context, it doesn’t tell much of the story of the life way of these people.”

In contrast, by studying the context of the artifacts found in the middens, scientists can learn a lot, including information about the presence of extinct animals which may be there. Middens have contained bones from now-gone animals such as the sea mink, which lived along the eastern coast of North America until it was killed off in the late 19th or early 20th century, and the great auk, a type of flightless seabird that went extinct in the mid 19th century.

“When that gets tossed aside, all the information about species diversity, size of individuals, presence of extinct animals, all that gets lost,” Kelley said of the practice of cherry picking artifacts from the middens. “Very often it ends up in a shoebox in someone’s house and people forget where it came from.”

Over the last two years, she and a crew from the University of Maine have been busy with the project, funded by Maine Sea Grant, to use ground penetrating radar to define the thickness and extent of many of the shell middens in Maine. The radar can’t replace excavation, in terms of recovering artifacts, but it has allowed Kelley’s team to fairly quickly evaluate the size of the middens. The project’s next step, she said, will be to develop a protocol for the network of citizen “midden minders” she is hoping to find here. She also will help set up a website so the citizen scientists can send in their photos and data. For now, though, prospective minders are invited to send her an email at to get on the list.

“We’re looking to perhaps work with land trusts or other conservation groups, to get them involved in monitoring what’s on their holdings,” Kelley said.

For example, midden minders could be asked to do a baseline survey of how much of an eroding bluff is visible, to describe the size or thickness of the midden that is exposed and to take photographs to add to a log of how things are changing over time.

“We know these things are eroding. We can’t stop the erosion,” she said. “And yet they contain so much valuable information that we really need to consider how we can bring in interested people to work together to recover information about this resource.”

The citizen science model has been successfully monitoring the health of middens in places like Scotland, Kelley said, and Sockalexis said it is possible it could work in Maine.

“It is important to preserve and protect midden sites as best we can, and having concerned local citizens and landowners monitoring these sites may have benefits,” he said. “They could provide regularly updated data on which middens are most susceptible to erosion due to storm surges, recreational usage and development projects.”

Sockalexis said he has been keeping an eye on a couple of shell midden sites for about a decade and in that time has seen large portions slump onto the beach to be washed away by the next high tide. He also has seen evidence of looting.

“To see how much they change year after year is almost heartbreaking at times,” he said of the middens.

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