Over the past 150 years, a significant change for the Willamette River has been the loss of its floodplain forests, which covered an estimated 89 percent of a 400-foot (120 m) band along each river bank in 1850.
By 1990 only 37 percent of this zone was forested; the rest had been converted to farm fields or cleared for urban or suburban uses.
The remaining forests close to the river include large stands of black cottonwood, Oregon ash, willow, and bigleaf maple.
The central valley—a former perennial grass prairie interspersed with oaks, ponderosa pines, and other trees—is devoted almost entirely to farming.
Douglas fir, western hemlock, and western red cedar dominate the forest on the Coast Range side of the basin.
Forests to the east in the Cascade Range include Pacific silver fir as well as western hemlock and western red cedar.

Fish in the Willamette basin include 31 native species, among them cutthroat, bull, and rainbow trout, several species of salmon, sucker, minnow, sculpin, and lamprey, as well as sturgeon, stickleback, and others.
Among the 29 non-native species in the basin, there are brook, brown, and lake trout, largemouth and smallmouth bass, walleye, carp, bluegill, and others.
In addition to fish, the basin supports 18 species of amphibians, such as the Pacific giant salamander.
Beaver and river otter are among 69 mammal species living in the watershed, also frequented by 154 bird species, such as the American dipper, osprey, and harlequin duck.
Garter snakes are among the 15 species of reptiles found in the basin.

Species diversity is greatest along the lower river and its tributaries.
Threatened, endangered, or sensitive species include spring Chinook salmon, winter steelhead, chum salmon, Coho salmon and Oregon chub.
In the central valley, several projects have been done to restore and protect wetlands in order to provide habitat for bald eagles, Fender's blue butterfly (of which 6,000 remain), Oregon chub, Bradshaw's desert parsley, a variety of Willamette fleabane, and Kincaid's lupine.
In the early 21st century, osprey populations are increasing along the river, possibly because of a ban on the pesticide DDT and on the birds' ability to use power poles for nesting.
Beaver populations, presumed to be much lower than historic levels, are increasing throughout the basin.
Over the past 150 years, a significant change for the Willamette River has been the loss of its floodplain forests, which covered an estimated 89 percent of a 400-foot (120 m) band along each river bank in 1850. By 1990 only 37 percent of this zone was forested; the rest had been converted to farm fields or cleared for urban or suburban uses. The remaining forests close to the river include large stands of black cottonwood, Oregon ash, willow, and bigleaf maple. The central valley—a former perennial grass prairie interspersed with oaks, ponderosa pines, and other trees—is devoted almost entirely to farming. Douglas fir, western hemlock, and western red cedar dominate the forest on the Coast Range side of the basin. Forests to the east in the Cascade Range include Pacific silver fir as well as western hemlock and western red cedar.
Fish in the Willamette basin include 31 native species, among them cutthroat, bull, and rainbow trout, several species of salmon, sucker, minnow, sculpin, and lamprey, as well as sturgeon, stickleback, and others. Among the 29 non-native species in the basin, there are brook, brown, and lake trout, largemouth and smallmouth bass, walleye, carp, bluegill, and others. In addition to fish, the basin supports 18 species of amphibians, such as the Pacific giant salamander. Beaver and river otter are among 69 mammal species living in the watershed, also frequented by 154 bird species, such as the American dipper, osprey, and harlequin duck. Garter snakes are among the 15 species of reptiles found in the basin.
Species diversity is greatest along the lower river and its tributaries. Threatened, endangered, or sensitive species include spring Chinook salmon, winter steelhead, chum salmon, Coho salmon and Oregon chub. In the central valley, several projects have been done to restore and protect wetlands in order to provide habitat for bald eagles, Fender's blue butterfly (of which 6,000 remain), Oregon chub, Bradshaw's desert parsley, a variety of Willamette fleabane, and Kincaid's lupine. In the early 21st century, osprey populations are increasing along the river, possibly because of a ban on the pesticide DDT and on the birds' ability to use power poles for nesting. Beaver populations, presumed to be much lower than historic levels, are increasing throughout the basin.
Willamette River