Snow droughts, deluge, and reservation systems interact to drive recreation access at Yosemite National Park.

Changes in snow extremes can have important but as yet underexplored impacts on the 1.2-trillion dollar outdoor recreation industry, impacting essential ecosystem services. These hydroclimate conditions interact with reservation systems used by park managers to manage potential impacts to park resources and visitor experiences. Climate change extremes and associated hazards limit and enable access in different ways: snowpack from extreme wet years can prolong road closures at higher elevations, while extreme snow drought enables early season access. Few studies have attempted to assess and compare the influence of snow conditions and reservation systems among a population of visitors, as we do at Yosemite National Park. Roads were still closed into the 2023 peak season from a record extreme snow deluge, yet entry was unrestricted due to lack of a parkwide day use reservation system. This combination led to higher overall visitation levels but spatially constrained visitor mobility and resulted in more crowded conditions and traffic congestion. We assess the efficacy of the day use reservation system in limiting use by comparing differences from the annual mean and monthly volume and timing of visitors. Results show that annual use levels are influenced more by managed access than by climate extremes, and that results differ by overnight use types and traffic count locations with seasonal access limitations. These results demonstrate a novel aspect of the impacts of changing climate extremes with human use of natural resources and suggest that appropriately managed reservation systems are an essential tool for managing recreation resources in a changing climate.