Ecologist shares findings on mystery of Mima Mounds

Linda Storm believes the Mima Mounds, those baffling bumps that pock the prairies of Southwest Washington, were ecological gold mines to the Indians who depended on the wild plants that grew on them.

For the past few years, Storm has been sharing her ideas mostly with local botanical groups and other like-minded ecologists, most of whom are familiar with the mounds and the curiosity they evoke.

Yesterday, the longtime Seattle wetlands ecologist and University of Washington doctoral student got a rare chance to introduce her ideas about the Mima Mounds to the American Association for the Advancement of Science meeting in Seattle.

Her talk was part of a panel discussion called "Reflections on the Salish Sea: Coast Salish Research and the Future of Pacific Northwest Ecosystems."

"I feel totally honored," said Storm, who has worked in the Seattle office of the Environmental Protection Agency for 20 years. "And kind of amazed, actually."

The Mima Mounds have been the focus of scientific study and campfire speculation since white settlers first set foot on the prairies that spread through what is now Pierce, Thurston and Lewis counties.

The mounds — neat, round bumps 30 feet across and about 6 to 8 feet high — once covered thousands of acres on the prairies, which Indians maintained by setting the land afire to keep back encroaching forests. Those forests have now largely covered the land that development and modern agriculture haven't already claimed.

Theories of the mounds' origin abound, and remain unproven. A popular idea is that the landscape graffiti was left by receding glaciers. Not-so-serious yarns include Paul Bunyan and his blue ox. One Indian legend says a great flood receded, leaving behind beached porpoises that became the mounds.

Storm says she leans more toward the geological explanations. But her research, which she is working into her Ph.D. dissertation, doesn't attempt to answer that question. Instead, as an ethnobiologist, she studies how the native people may have used the mounds to their advantage.

The Indians harvested many wild plants that sprouted on the prairies, perhaps none more important than the bulbs of the blue-flowering camas lily that still carpet the wavy landscape. The Indians ate the staple vegetable year-round, raw or baked, or pressed and preserved in flat cakes, which could be added to stews or used to sweeten boiled salmon.

Storm is attempting to prove that the repeated hills and dales of the Mima Mound prairies, long discounted on settlers' maps as second-rate growing land, created a uniquely varied ecosystem that allowed more diverse plants to grow and made for longer growing seasons.

To prove it, she has been performing tests on the mounds to determine whether they hold moisture and heat better than the troughs between them.

She hopes she may even be able to help show that the benefits of the mounds may have helped Indians settle in the area many thousands of years ago, and sustained them generation after generation.

Dave Peter, an ecologist for the U.S. Forest Service who studies the prairies, said it has long been observed that camas blooms at different times on top of the mounds than at the bottom.

"These ideas are pretty well accepted," he said.

"But she is among the vanguard of scientists who are actually documenting it and putting it into some formal record."

Ian Ith: 206-464-2109 or iith@seattletimes.com