The park preserves a variety of ecosystems from coastal dunes, estuarine mudflats and tidal marshes to shrub wetlands, temperate rainforests and swamps. Situated within the Sitka spruce vegetation zone, its forests are dominated by conifer trees and carpeted with a great diversity of understory shrubs, ferns and wildflowers. Extensive wetlands in the park include fringing saltmarshes on the lower Columbia River, the tidally-influenced lower Lewis and Clark River and many low-gradient brackish sloughs and marshes. Freshwater streams and springs are numerous in park forests, and freshwater ponds are found in various habitats. These wetlands provide valuable habitat for a diversity of mammals, birds, reptiles, amphibians and fish.