The spots on the trees in Imanta that caused people’s concern – lichens that indicate cleaner air / Article

The program received calls from worried residents of Imanta that a strange disease has taken over the trees in the forest of the Riga micro-district – they are covered with white spots, and the forest has become almost mottled. Whites are mostly seen on the trunks of deciduous trees.

The representative of the Nature Protection Board, Artūrs Jansons, who joined the program for a walk in this forest, explained that it is one of the lichens. There are more than 700 lichen species in Latvia and many of them do not even have a Latvian name. “This particular one, which looks like a patch of paint – the best comparison is what it looks like – it is a lichen species Phlyctis argena. There is no Latvian name, the audience can guess what it could be called, and it is an absolutely common lichen, who lives on leafy trees.”

Lichen is a very interesting “co-production” of algae and fungi, which requires such modest conditions for its survival that it will be the last to disappear even if the entire plant kingdom perishes in the world, but it has a catch – lichen is very sensitive to air pollution, especially against sulfur and nitrogen compounds in the air.

Jansons pointed out: “When the problem of these acidic rains was very relevant in Europe, when most boiler houses were fired with coal, which produced sulfur dioxide emissions, lichens had a bad time, because these acidic rains pretty much destroyed lichens. At the current moment in Europe and Latvia the air quality has improved a lot compared to those times, and the living environment is favorable for lichens. In fact, lichens are such an indicator of clean air. If lichens grow and grow well, it means that the air is clean.”

It seems that the lichens have multiplied considerably in the Imanta forest this year, so they have become more noticeable. Then, when the forest dries up and other colors appear in it, the formations on the deciduous trees will no longer be so conspicuous, explained the Nature Protection Board.

In addition, the white spots on the trees do not indicate something bad, but on the contrary – that everything is in the best order with air quality in the Imanta forest.

On the other hand, as biologist and naturalist Ilmārs Tīrmanis explained about lichens in his article on LSM.lv, a poor substrate is sufficient for the life of lichens, because they take in both nutrients and water directly from the air. Lichens are therefore very sensitive to air cleanliness, as pollution interferes with lichen photosynthesis. And at the same time – that’s why they can be seen almost everywhere, where the air is not too polluted, you just have to look closely.

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