Much of the ecology of the watershed have been affected by wildfires and forestry , and is considered to be in a seral phase . The river travel through several different vegetation zones . In its upper reaches , the Adams flow through the Interior Cedar Hemlock zone . These forests are similar to the coastal forests of British Columbia and contain old @-@ growth tree up to 1000 years in age . Old @-@ growth stand along the river also contain rare species of lichen , likely isolated by the last Ice Age . The floodplain of the Upper Adams contain wetland species of deciduous trees such as black cottonwood as well as a dense layer of shrubs including black twinberry , red @-@ osier dogwood , and thimbleberry . The lower river is dominated by the drier Interior Douglas Fir vegetation zone . Other conifer species present are Ponderosa pine , Engelmann spruce , and alpine fir . The area around the river mouth have been altered by human activities such as farming and livestock grazing .