105 



of watersheds and river reaches having high ecological integrity and high conservation 

 value for sustaining sensitive aquatic species. This pioneering effort provided the 

 initial prototype and template for the Scientific Panel on Late Successional 

 Ecosystems' "Watershed Option," proposed to Congress in 1991 for protection of 

 salmon and other aquatic species on federal lands in the Pacific Northwest. 



Role of Habitat Deterioration in Salmon Declines 



Obviously, salmon and other fishes are adversely impacted by many factors 

 other than land use activities, from dams and fishing to fluctuations in the marine 

 environment. At the least, deterioration of freshwater habitat synergistically 

 aggravates problems caused by other factors, by limiting the ability of fish populations 

 to adapt to and compensate for stressors elsewhere in their life cycle (see Bisson et 

 al. 1 991 ). In other cases, fishing and dams are clearly not an issue and it is extremely 

 difficult to ascribe declines and extirpation in some fishes and sensitive amphibians to 

 causes other than damage to freshwater habitat (Frissell 1991, Frissell in press). 



It is important to keep in mind that the native freshwater fauna of the Pacific 

 Northwest evolved under cold, wet conditions that prevailed during the Pleistocene 

 period of about the past million years. During this period, forest or cold tundra-type 

 conditions existed across most of the region. Fish species and other organisms 

 adapted to cold, clean waters-the Pacific salmon and trout species, lampreys, and 

 others-became widely distributed. Therefore the native aquatic fauna of this region, 

 and thus its fishery resource, is largely dominated by animals that are inherently 

 sensitive to the warming of surface waters, sedimentation of streambeds, and loss of 

 channel stability and complexity that virtually always occur in response to disturbance 

 and depletion of forest cover. Some species requiring extremely cold waters, such as 

 the bull trout and tailed frog, were undoubtedly very abundant in the past, but now 

 have receded and fragmented into small, isolated populations in mountainous 

 headwater areas (see references in Frissell 1991, Frissell in press). 



During the past century of development by European man, one of the most 

 extensive changes on the landscape has been the logging and clearing of what once 

 were old-growth and mature forests. Early development was concentrated in low- 

 elevation areas, where many aquatic species were directly impacted by the loss of 

 forest cover and simplification or outright destruction of natural estuaries, wetlands, 

 floodplains, and riverine habitats. Human disturbance of forests occurs at frequencies 

 and a spatial extent far in excess of natural disturbances such as wildfire and floods. 

 Deforestation and accelerated forest disturbance , in conjunction with a sensitive native 

 fauna, have contributed to widespread decline and fragmentation of the populations 

 of fish and other aquatic animals (Frissell in press; Bisson et al. 1991). 



