In simple terms, a lichen is two (sometimes three) organisms in one. A more technical description is that lichens are a composite organism that emerge from algae or cyanobacteria (or both) living among filaments of a fungus in a mutually beneficial (symbiotic) relationship.


Lichens are not only interesting to study, they are often quite beautiful in form and colour. They are also easy to find (because they maintain their structure all year round) and they exist in just about every environment on Earth. They can be found on rocks, stone walls, gravestones, trees, fence posts and such like, from the Arctic to hot deserts, from rain forests to temperate woodlands. They have been found living inside rocks in the spaces between the rock grains and will even survive in toxic slag heaps.


Even more astonishing is the fact that in 2005 two species of lichen were launched into Earth orbit and exposed to the vacuum of space for 15 days without any noticeable side-effects.


Lichens do not have roots, so although they attach themselves to rocks and trees they do not feed on them. Instead they must take the light, water, and nutrients they need to survive from their surrounding environment, i.e., the atmosphere. Certain species of lichen are very sensitive to pollutants in the air (especially sulphur dioxide) so where there is too much pollution they will not be found. In city centres and near industrial areas only the most tolerant species will be found. In more rural areas the number of species will increase as the air quality improves. So in the same way that invertebrates are used to indicate the quality of water, lichens can be used to indicate the quality of the air.


Monitoring air quality (and looking beautiful) is not the only thing that lichens are good at. For example, the pH indicator in litmus paper is a dye extracted from lichens. Other lichen dyes have been used to colour clothing. Lichens are used in both traditional and modern medicine. They are often the only available food source for reindeer and other grazing animals.


To finish off this first report here are a few of the lichens we’ve spotted on a recent walk around the site. They are mainly ‘Crustose’ species attached to the stone walls that have been here for many years, but we have found one ‘Foliose’ species on one of our new fence posts. This is most encouraging.



More articles on lichens can be found below as and when we add them.