The U.S. Army Corps of Engineers has dredged the lower Columbia River since the 1860s, carving and maintaining the deep shipping channel that links Portland to the Pacific Ocean. The agency says the work is essential to international commerce — yet remarkably few studies have examined its ecological toll on the river system.

OPB’s “Think Out Loud” takes a closer look at both sides of that ledger. Tribal leaders say dredging has contributed to the decline of lamprey, steelhead, and other culturally significant species that depend on the Columbia estuary, while hydropower dams have caused sediment to pile up in the mid-Columbia, slowing the river’s flow and pushing water temperatures to dangerous levels.

The conversation features freelance journalist Josephine Woolington, who recently reported in depth on the river’s shifting ecological and economic functions.

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