The effects of climate change on the timing of peak fall foliage in Acadia National Park

Abstract

Context: In recent decades, most United States’ National Parks have experienced extreme temperature and precipitation regimes outside of their historical ranges of variability with unknown effects on fall phenology. Objectives: We determine 1) how seasonal climate in Acadia National Park, Maine and the timing of peak fall foliage have changed between 1950 and 2021; 2) how changes in seasonal climate have affected fall foliage; and 3) how we might expect the timing of fall foliage to change given future climate projections. Methods: We use ERA5-Land data to analyze changes in climate. We couple remotely sensed data with archival research to determine changes in the timing of peak fall foliage. We use multivariate regressions to understand the relationship between climate and fall foliage. We use CESM2 data to predict the timing of peak fall foliage coloration through 2060. Results: Minimum temperatures, maximum temperatures, precipitation, and the number of warm nights, hot nights, warm days, hot days, and downpour days have all significantly increased (p ≤ 0.05). The timing of peak fall foliage is now occurring almost two weeks later (p ≤ 0.05). September temperature and precipitation and May precipitation were positively correlated with delayed peak fall foliage. Early October precipitation was negatively correlated. Future climate projections predict the timing of peak fall foliage to occur between October 30 and November 2 by 2060. Conclusion: Understanding how climate is affecting leaf senescence both is crucial in a national park where fall tourism brings large gains to the local economy and provides key information to park managers planning for a resilient, sustainable future.