This IBA is located within the most intact deciduous forest in Polk County. It encompasses Straight Lake State Park, Straight Lake State Wildlife Area, and two State Natural Areas—Tunnel Channel Woods and Straight Lake Tamarack Fen. The site includes Straight Lake, a wild, undeveloped lake drained by the Straight River; the adjacent wetlands, which are a diverse mosaic of sedge meadows, alder thicket, open and forested bogs, hardwood swamp, and ephemeral ponds; and a core of mature forest surrounding the wetlands. Oaks and hickories are common, with maples, basswood, and birches on north-facing slopes. Pockets of white pine, yellow birch, and tamarack are found throughout.
Straight Lake is significant for breeding forest birds, notably cerulean warbler, found here breeding in unusually high densities and well north of the core of its range in Wisconsin. Others breeders include black-throated blue warbler (at its westernmost range limit), red-shouldered hawk, American woodcock, Eastern wood-pewee, yellow-throated vireo, veery, and Canada warbler.