Areas that have been logged are far more likely to suffer from major landslides and erosion events which deposit abnormally high levels of sediment into area streams. Logging and the roads created to facilitate logging also significantly degrade stream ecosystems by introducing high volumes of sediment into streams, changing natural streamflow patterns, and altering stream channel morphology.
Logging removes large trees that normally fall into streams and provide shelter and thermal cover, raises water temperatures and pH, and degrades the chemical and ecological conditions and food webs that fish need to survive. The end result of logged landscapes is a highly altered forest system which creates significant problems related to erosion, sedimentation and altered stream flow patterns. Logging activities have numerous impacts on aquatic systems in the Sierra Nevada. Roads also serve as vectors for the spread of disease by allow an easy access point for a potential threat that otherwise would not have been able to access this intact forest. The increased traffic and activity on these logging roads allows for the introduction of invasive species which can quickly overrun native species and thus greatly altering the natural balance of the forest ecosystem. Road creation also leads to the increased prevalence of non-native species and diseases. Aquatic species dependent on clean, clear water, are greatly impacted by this sudden change to the aquatic environment. Roads direct and increase the runoff of soils into area streams and rivers adding a high volume of sediment and pollutants onto these watersheds. Roads break-up the existing soil and remove the ground cover that assists in the natural distribution of rainfall and runoff. The creation of logging roads also greatly impacts the aquatic systems on the forest by introducing increased erosion and sedimentation into the area. There are more miles of roads in our national forest system than in the rest of the entire continent. Many species are unable to cross these barriers and therefore have their range and distribution altered, oftentimes leading to drastic consequences on a local scale. Roads fragment and divided the forest, creating barriers for wildlife dispersal and migration. Road building during logging operations directly leads to many negative consequences for wildlife, aquatic health, and the ecological integrity of the forest. Below are some of the negative impacts that logging operations can have on the forests of the Sierra Nevada. However, irresponsible and misguided logging prescriptions are not only bad public policy but are also likely to degrade the ecosystem functions of our national forests, increasing the likelihood of future severe fires, increasing greenhouse gas emissions, and impacting other resource values. A fire resilient forest is one that can survive regular fire, as these forests once did before the era of intensive logging and fire suppression. Nevertheless, we also know that in some cases a responsible thinning operation is needed to reduce the fuel profile to promote fire resiliency.
Logging operations on the national forests of the Sierra Nevada continue to have a significant detrimental impact on the ecological health of these vital forest systems.