Hoping for global warming after a cold winter... and lichens as bioindicators of climate change

This month's topic is March and green. Of course, everybody by now is anxiously waiting for spring, to get rid of the polar vortex. Hopefully that will happen soon! By the way, the expanded polar vortex that affects large parts of North America with bitter cold is a direct consequence of global warming!

Unlike most plants and animals, and mushrooms for that matter, lichens are perennial organisms that do their thing year-round. In fact, some lichens growing on the ground take advantage of the snow cover creating a green house effect above them, to continue their metabolism when most trees are leafless and bears and other mammals hibernate. Lichens exposed on rocks and tree bark easily withstand temperatures below 0 degrees Fahrenheit or minus 20 degrees Celsius, with felt temperatures even lower in wind-exposed areas, whereas we humans get our face frozen under similar conditions. Well, lichens have been exposed to cosmic radiation in outer space, so these critters must be tough indeed.

One particular group of lichens that is more sensitive to climate and especially to frost are those growing as epiphylls on living leaves of plants. Therefore, these epiphylls are not usually found in temperate regions. However, global warming is causing their expansion into areas of eastern North America and central Europe, where they have never been observed before based on herbarium collections. A sure indication that climate change is for real.

The pictures show the tiny lichen Gyalectidium setiferum, characterized by forming hyaline hairs, which is spreading in central Europe on suitable evergreen plants.