Lichens live all over the planet in many varied habitats, some of which are more pleasant than others. Lichens are very common in extremely frigid temperatures, including Arctic climates. In some cases, lichens are the only signs of life around. On the other hand, the creatures also are prevalent on trees, in grasslands, in rugged coastal areas, deserts, rainforests and even on walls. Environment can be a source of extreme stress on lichens, particularly with regards to extremes of cold and heat and too much water. Dry air and drought conditions also can be very problematic for lichens.
To be a suitable living setting for lichens, several fundamental necessities exist, one of which is water. Lichens lack waxy cuticles, and therefore are unable to save water. As a result, lichens frequently appear on coasts near water. The creatures do not live inland due to low humidity levels. Clean, quality air is also vital for lichen survival and thriving. Via the cortex, the creatures take everything in, including substances that may be harmful. Because of this, lichens are not common in large metropolitan areas with excessive pollution from cars or manufacturing plants. For photosynthesis purposes, light is necessary. Lichens need nutrients in their environment as well, namely oxygen, carbon and nitrogen.
Lichens grow over substrates, which are their "residences." Some lichens are capable of living on a wide variety of substrates, while other kinds are strictly attached to one. For example, lichens that live over rocks need alkalinity, which they can get from limestone. However, acidic rocks like basalt cannot work with these kinds of lichens. Also, if a dirt is alkaline, it also is beneficial for lichen inhabiting. Other examples of possible substrates are trees, vehicles and even human homes.
Lichens work well in places where they can go undisturbed and without stress, for the most part. This is due to the fact that lichens are very sensitive to changes in environment. In more urban settings, the creatures can often be found in places such as churchyards, which do not get a lot of traffic and are usually very quiet. Lichens can often be found on the flat, smooth surfaces of headstones. Due to the preference for undisturbed spots, lichens are very common in ancient rainforests that have barely been touched by humans and time.