Fungal spore seasons advanced across the US over two-decade climate change

Abstract

Phenological shifts due to climate change have been extensively studied in macroorganisms, yet the responses of fungal spores—crucial microorganisms that act as airborne allergens and play important roles in ecosystems—remain understudied. This hinders our understanding of global change impacts and its implications for both ecology and public health. To bridge this gap, we leveraged a long-term, continental-scale dataset of airborne fungal spores collected by the US National Allergy Bureau. We extracted ten metrics describing the timing (e.g., start and end of season) and intensity (e.g., peak concentration and integral) of fungal spore seasons from both ecological and public health perspectives, defined with percentiles of total spore concentration and allergenic thresholds of spore concentration, respectively. Using linear mixed effects models, we quantified temporal shifts in these metrics across the continental US. We revealed that the onset of the spore season has significantly advanced from both ecological (11 days, 95% confidence interval: 0.4 ~ 22 days) and public health (31 days, 14 ~ 48 days) viewpoints in two decades. Accordingly, the ecological spore season and allergy season tended to be longer. Nevertheless, the total spore concentration in an ecological spore year and in a spore allergy season tended to decrease. The start of the spore season was significantly correlated with climate change variables, such as temperature and precipitation. Overall, our findings suggest possible climate-driven advanced and prolonged fungal spore seasons, highlighting the importance of climate change mitigation and adaptation in public health decision-making