Lichens are longed lived symbiotic organisms where a primary heterotrophic fungal partner forms the lichen body (thallus) to host and obtain energy from a heterogeneous photobiont community (unicellular green algae or cyanobacteria). Other bacterial and fungal communities with yet unknown roles were recently described as additional symbionts. Lichens live in a wide range of terrestrial biomes: from tropical forests to mountain peaks, and from frozen tundra to hot desserts. In the vast Arctic region, where few plants survive, lichens thrive. They can sustain drastic temperature shifts; survive gamma radiation, intense UV-light and even Mars-like conditions. Yet, despite their tremendous sturdiness, their Achilles’ heel is pollution. Although some species can adapt and thrive in polluted environments for their vast majority the exposure to nitrogen oxides (NOx), sulfites and heavy metals is detrimental or even fatal. In this study we will investigate using molecular data how lichen communities respond to 1) drastic temperature fluctuations and 2) to pollution. We will specially focus on photobionts but also consider the other symbiotic players (the fungal host and the associated bacterial communities).