Increasing wildfire smoke has limited impacts on national park visitation in the American West

Abstract

Ambient wildfire smoke in the American West has worsened considerably in recent decades, while the number of individuals recreating outdoors has simultaneously surged. Wildfire smoke poses a serious risk to human health, especially during long periods of exposure and during exercise. As such, evaluating whether people modify recreation in response to smoke is important to understanding the public health implications of these trends. Here we aggregate data on black carbon, a major component of wildfire smoke, and recreational visitation in 32 US national parks from 1980 to 2019 to examine how visitors respond to wildfire smoke. We hypothesize that visitor response may exhibit a threshold effect where ambient smoke reduces visitation after a critical level, but not before. We develop a series of breakpoint models to test this hypothesis. The results of these models are mixed, but overall show little to no effect of ambient smoke on visitation to the 32 parks tested, even when allowing for critical thresholds at the extreme upper ranges of smoke exposure. This indicates that wildfire smoke does not greatly alter park attendance. This finding suggests that management actions to protect visitor health during smoke events may be warranted.