The reevaluation of the lichens' risk to extinction has already begun in 2019, with five distinct surveys for distinct lichen families. Biologist Polina Degtjarenko of the University of Tartu assessed the threat status of previously unassessed lichens using international (IUCN - International Union for Conservation of Nature's Red List of Threatened Species) criteria and revised the extant conservation categories of protected lichens.

Nearly all lichens in Estonia, or 96 percent, are assessed are now assessed for vulnerably and placed on the Red List, and represent a sizable Estonian category by themselves. This has become an important starting point for determining the conservation requirements of lichens.

The survey found that of Estonia's 978 lichens, 415 species are threatened, i.e. critically endangered, endangered or vulnerable, and 104 species are near threatened. Slightly more than one in three, or 344 species in total, are in vulnerable status. The remaining species are distributed among the other categories of the Red List: they are either regionally extinct in Estonia (25 species), have missing data (64 species), or remain unassessed. The 34 species for which there was no documented herbaceous material were not included in the Red List procedure.

Extensive need for protection

Estonia first protected lichens in 2004; however, the initial inventory of 51 protected species has not been revised or updated since then. Now the researchers revised the protection categories for species that were already protected and submitted a proposal to the state to modify or maintain the categories of lichen species and to increase their protection.

Based on the results of the current study, the scientists did not exclude or downgrade any of the existing protected lichen species. "Previous Red List assessments have also shown that the Estonian lichen fauna contains endangered species, but the number of endangered species is now unexpectedly high," Degtjarenko, the lichen expert who led the study, said.

According to the their proposal, the 93 lichen species in need of protection are categorized as follows: Category I - 25 species, Category II - 59 species, Category III - nine species.

In Estonia, threatened lichens inhabit mainly forests (particularly dry boreal and nemoral deciduous stands), alvar grasslands and various saxicolous habitats, but also wooded meadows, parks and limestone quarries and dunes. These are 53 species in total. This is understandable, forest lichen species are the most endangered, as harvesting pressure in both commercial and semi-natural forests in Estonia has been high over the past several decades.

The wooded habitats provide several specic microhabitats for epiphytic and wood-dwelling lichens, like rough bark of coniferous and deciduous trees, wood of standing and laying tree trunks, charred wood, etc. But also dry alvar grasslands with very thin soil layer and sand dunes are suitable for ground layer lichens.

Therefore, the main threat factors of Estonian lichens tend to be forest cutting (important factor for 96 species) and overgrowing of dunes and alvars due to the cessation of traditional management (important for 70 species). Also, the air pollution, expansion of urban areas and tourism activity also have negative impact for several lichen species.

"Intensive forestry activities, the reduction of old broadleaved trees in cultural landscapes, encroachment of open or semi-open habitats and encroachment of old-growth stands are the most significant risk factors for lichen in Estonia," Degtjarenko said.

"Loss of old wooden buildings, the pollution of small streams and alteration of the water regime of wetlands, over-clearing or overgrazing of wetlands, construction, and limestone mining also endanger species with specific habitats," the researcher said.

The study on the endangered status of lichens was supported by the The Environmental Investment Center (EIC) with funds from the project "Assessment of the endangered status of lichens and their conservation status in Estonia." Experts Tiina Randlane, Inga Jüriado, Piret Lõhmus, Liis Marmor-Ohtla and Ede Oja also participated in the identification of lichens in need of protection.

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