Lichens declining at an increasing rate
Photo: Kimmo Jääskeläinen
The proportion of threatened lichen (Lichenes) species has doubled since the 2000 evaluation. In order to halt the decline in lichens, conservation efforts must be intensified, especially in old-growth forests and on calcareous rock outcrops in Southern Finland. Conservation is currently insufficient in all lichen habitats.
The evaluation included 1,594 lichens and 238 lichen-like or lichenicolous fungi. The number of species classified as either threatened or Regionally Extinct increased by 145, and the proportion of threatened and Regionally Extinct species has doubled since 2000. Fifteen per cent – 271 species – were classified as threatened, while 43 species were classified as Regionally Extinct.
The most threatened lichens grow on calcareous rock outcrops
The most important habitats for lichens are rock outcrops (44%), forests (38%), shores (7%) and bare fell areas (6%). Fifteen per cent of lichens growing on rock outcrops are threatened. The proportion of threatened forest and fell lichens are 13 and 19 per cent respectively. As many as a third of all species growing on calcareous rock outcrops are threatened.
Since the last evaluation, not a single threatened species has seen a recovery in population sufficient to warrant a downgrade in threat status. The status of a few lichens was downgraded when their populations were found to have been stronger than previously thought. The major reasons for upgrades in status were an increased level of knowledge (142 species), an altered interpretation of the criteria (94 species) and a genuine change in status (49 species). New data has primarily been collected on lichens growing in forests and on calcareous rock outcrops.
Forest lichens declining
The rate at which forest lichens are declining has accelerated. For example, the population size of seaside kidney (Nephroma laevigatum), which grows on deciduous trees in old heath forests and herb-rich forests, is reducing at a faster rate than previously and its status has been raised to Critically Endangered. One fifth of all forest species previously classified as Least Concern are now classified as threatened or Near Threatened.
Logging and a reduction of old-growth forests and old trees constitute the major threats to lichens. They are the primary threat to 43 per cent of threatened lichens. Construction poses a threat to a fifth of threatened lichens, especially those inhabiting forested shorelines and rock outcrops, and calcareous rock outcrops in particular. Air pollutants and climate change also constitute significant threats to lichens.
Hardly any new conservation areas for lichens
The conservation of lichens and their habitats has mainly focused on the implementation of existing programmes. Few new conservation areas have been established, and hardly any decisions have been made on setting the boundaries of areas containing strictly protected species. The most important habitats for lichens, old-growth forests and calcareous rock outcrops, are not among those protected under the Nature Conservation Act. Logging that endangers threatened lichens is generally allowed in habitats protected by the Forest Act. Large numbers of deer (Cervidae) prevent the regeneration of deciduous trees in conservation areas, causing a decline of lichens of old deciduous trees.
A reduction in the amount of nitrogen deposition has not been achieved. Tree growth in Finland has doubled over the past 50 years, and too much shadow cast by the forest canopy inhibits many lichen populations. Forest use has also become more intensive, as stumps and even twigs are now collected for use in bioenergy production. It’s probable that this worrying decline in the habitats of threatened lichens will continue in coming years.
- Planning Officer Kimmo Jääskeläinen, University of Helsinki, tel. +358 (0)40 5899 158, firstname.lastname@example.org
- Senior Research Scientist Juha Pykälä, Finnish Environment Institute (SYKE), tel. +358 (0)400 148 664, email@example.com