The estimated number of fungal species worldwide

The current panel shows Kew’s 2023 synthesis: a range of 2–3 million species and 2.5 million as the best working point. This is not a global census of all fungi but a synthesis of several lines of evidence, including fungus-to-plant ratios, intensive studies of selected sites and environmental-DNA sequencing. The older 2.2–3.8 million range from 2017 remains in the article as a dated comparator, but it no longer describes the chart’s bounds.

The range is wide because many organisms do not form easily noticed fruiting bodies, live briefly, or have been detected only as a sequence. The same genetic lineage may later prove to be several species, and different names may be merged after revision. It is also necessary to decide how we define a species in organisms reproducing asexually or known from few markers.

The figure does not say how many species occur in Poland, or how many of them can be seen on a walk. It includes yeasts, microscopic parasites, symbionts and fungi of aquatic environments alongside larger species. Nor is it a number of threatened taxa. It serves as a denominator showing the size of the gap in knowledge: described species probably constitute only about four to seven per cent of the predicted diversity.

The 2017 estimate remains a point of reference, not an eternal constant. New methods and better sampling may shift both bounds. MykoRadar therefore shows the year, the method and the level of confidence, instead of presenting one striking figure without context. The honest reading is this: we know the order of magnitude and we know that undescribed diversity is very large, but we cannot count it to the nearest hundred thousand.

How the newer interval was built

Kew’s 2023 synthesis did not select a single older extrapolation. It compared four broad methods: scaling laws, fungus-to-plant ratios, rates at which species are found, and environmental-DNA studies. After weighing their limitations, the authors adopted a 2–3 million range and 2.5 million as the best working point. This is neither a count of living organisms nor a confidence interval from one model.

Against about 155,000 formally named species, the known share is 6.2% of the central estimate. That comparison remains approximate: changing species concepts, synonymy and new sequence data can alter both the numerator and the denominator.

Which value the panel uses

The lead, method and chart refer to Kew’s 2023 synthesis: 2–3 million, with 2.5 million as the working centre. The 2.2–3.8 million range describes the older 2017 state of knowledge. Comparing the versions shows how methods change, but the current denominator must not combine bounds taken from different reports.