Such species are slow to return to areas from where they have disappeared, so their presence is evidence of a long continuity in forest ecosystems.
[3] Indicator fungi were selected to the list keeping in mind that they should not be too difficult to identify, and should not include taxonomic pitfalls.
To minimize the effects of accidental single omissions of observations, the number of the so-called indicator species was kept fairly high.
[citation needed] The total sums of these numbers can be used as reference values for each area as follows: This rating is fairly strict.
Also Bonsdorff et al. (2014) have published lists of mushrooms and other terrestrial macrofungi that indicate the biodiversity of various forest types in Finland.