Temporal changes in macrofungal alpha diversity over four decades in Europe

Terrestrial organisms have shown mainly positive or neutral changes in local richness across late- and post-industrial decades. A lack of time-series data has so far hindered the exploration of similar changes in fungal alpha diversity. Here, we analysed 5 million macrofungal records and tracked changes in alpha diversity between the 1980s and 2010s across 500 time comparisons. Using a novel tool to standardize for geographic spatiotemporal sampling effort, we estimated alpha diversity using coverage-based rarefaction and extrapolation. We found weak positive net changes in alpha diversity across most of Europe. Drier conditions and nitrogen increases were linked to fungal alpha diversity decreases, while climate warming increased alpha diversity across fungal functional groups. Our results suggest that local-scale factors, such as drought and chemical pollution, are more constraining to fungal biodiversity than regional-scale climate warming and habitat loss.