Parks Stewardship Forum

US national park managers must address a complex portfolio of foreseen and unforeseen challenges that arise in part from a dual mandate to preserve nature and facilitate visitation. To deal with resource management challenges, managers can identify potential pathways toward a solution through the use of science to inform policy and guide actions. The way science has been applied has evolved over the course of the National Park Service’s history, in large part due to the prevailing societal context and ways of thinking about the environment, and relatedly as a necessity to mitigate the impact from development and anthropogenic climate change. Landscape-scale environmental hazards are a fitting proxy to recount the changing use of science and policy because biophysical processes become most hazardous at the interface of infrastructure and the natural environment, where people are most exposed. This paper synthesizes modern administrative and environmental histories of hazards in Yosemite National Park from the late19th century to the early 21st century through archival records and long-term data, including significant events and trends in wildland fire, tree mortality (falls), extreme floods, and rockfalls and slides. Findings confirm increased severity and extent of wildland fire, correlations between periods of drought and high rates of tree mortality, warmer precipitation events lead to earlier annual peak streamflow, and connections between periods of prolonged cold with rockfalls, and prolonged precipitation with slides. These hazards exist as an interconnected system in the context of high seasonal visitation, and while there are averages of seasonal conditions over time, there are no “normal” years.