As an aside, I'm always perplexed by these statements:

> There are as many as 12 million species of fungi, yet there are just 155,000 or so known species, leaving vast numbers undescribed.

"There are as many as 12 million species of fungi, yet there are just 155,000 or so known species..."

The second number makes sense: it's how many species we've identified. But the first number... how can we know how many we don't know?

This kind of thing pops up all the time (X number of crimes go "unreported"... if they're unreported how can we say that?).

I get that they may be estimates. If so, it's pretty important that that estimation process is described.

Might as well say there are as many as 12 trillion species of fungi.

It's probably something like, here are the environments where we've done comprehensive surveys, here are the kind of different situations where we expect to find different species (decomposers of various types, mycorrhizal, within plants, within animals, on surfaces, specialists, generalists, climates, etc). Multiply the species from places where we've probably found most of them by the number of places where we've only found the most obvious fungi. However it works it's going to have big error bars, reflected in the fact that 12M species is the upper end of a range starting at 2.2M.

There's probably a really good answer using statistics, but it's beyond me.

> 12 trillion species of fungi

Give it enough time, it could happen