GBIF records show later autumn mushroom dates after 2007 in most of 11 European countries, but perennial polypore records show that changes in recording time can cause shifts of the same size

Question: Kauserud et al. (2012) reported later and wider autumn mushroom fruiting seasons in Austria, Norway, Switzerland and the United Kingdom in 1970-2007. Did this continue, and do record dates show fruiting or recording time? Approach: We used 7.2 million cleaned GBIF records (cloud snapshot 2026-10-01) of short-lived mushrooms in 11 European countries, 1970-2025. We calculated species-mean trends in record date with joint species and year-block bootstrap intervals. We added three controls: seasons of exactly 20 random records per species-year; 1.0 million records of perennial polypores, whose fruit bodies are present all year, so that their record dates show recording time; and CRU TS late-summer temperature and rain. Results: In 1970-2007, mean record dates became later in the four original countries (+1.7 to +2.4 days per decade); the interval was above zero only in the United Kingdom. With equal samples, the season did not become wider in Austria, Switzerland or Norway, and the United Kingdom widening fell from +9.2 to +3.3 days per decade (interval includes zero). In 2008-2025, mean dates became later in 10 of 11 countries, with intervals above zero in Austria, Denmark, the Netherlands, Belgium and Germany (+5.8 to +10.1). Mushroom record dates were 2.5-5.6 days later per degree C of August-October warming in most countries. But polypore record dates also became later in warm autumns, by +7 to +11 days per degree C in Norway, Sweden, Finland, the Netherlands and France. Pooled polypore dates became later in 2008-2025 in Belgium (+14.7) and the United Kingdom (+5.4). Mushroom-minus-polypore contrasts were not clear in most countries with all recorders together, but were positive within recorders, because polypore dates became earlier within recorders. Conclusion: GBIF data agree that recorded autumn mushroom dates became later after 2007, but they do not support a general wider season. Changes in recording time can be as large as the shift, and the two controls disagree, so record dates alone cannot show a change in fruiting. Limitation: GBIF has few records before the 1980s-1990s for Austria, Switzerland and Norway, and the polypore control partly follows mushroom trips.

fungal phenology · mushroom fruiting · GBIF · recording effort · citizen science · climate change · Agaricales · phenology · sampling bias · replication · Europe · CRU TS