Interesting Things About Lichen

With muscles stiff from last night's pilates class and a brisk breeze in my face, the body was feeling its age as my morning walk took me along a little-used road at the edge of town. A person could collapse on this road and no one would come along for hours, was the gloomy thought that flashed through my mind. As I thought this, I looked down at the road surface and noticed it was covered in lichen, then remembered a book I'd read years ago that included some amazing information about lichen.

I suppose nearly everyone knows that lichen is a symbiotic relationship between fungi and algae. Nestled among the mats of fungal hairs (hyphae) are minute single-celled algae. Lichens are exremely drought hardy and can survive the harshest summers on rocks and roofs exposed to the full sun. They might look dry and dead, but it only takes some rain to reinvigorate them.

Surprisingly then, they are very intolerant of air pollutants. So much so that they are used as biological monitors. Different types of lichen react to different types of pollutants. Some are useful monitors of sulphur dioxide, a common industrial pollutant, as they are unable to survive when it is present. The number of lichens increases with distance from industrial areas. In areas or towns where the air is unpolluted, lichens thrive. I've often noticed the lichens growing on old tile roofs around the country town I live in. Sometimes there will be a streak of clean roof standing out from the lichen-encrusted tiles, where the smoke from a chimney blows across it and I wonder what is burnt in that fireplace.

Other lichen species are sensitive to acid rain, airborne heavy metals and radioactivity. These latter can be used as a record of accidents at nuclear power plants or of atmospheric testing of nuclear weapons.

As well as their use as biomonitors, lichens do have a more down-to-earth use. When we lived a fairly self-sufficient life on a small, rocky acreage, I once used lichen collected from the rocks to dye some hand-spun angora fleece (shorn from our own goat), which I then knitted  into a jumper for my son. The colour turned out to be a mustardy brown. The photo below shows the type of lichen used for dyeing.

Lichen is often found in conjunction with moss. Mosses are also sensitive to pollutants, and some species accumulate toxins which can be analysed to show patterns of pollution from industrial sources.

The above uses only scratch the surface. Lichens have been used as food and in medicine, perfumery and embalming, and for much else besides. Some lichens are poisonous, so please don't go putting your local species in a salad. An interesting medicinal application is that about half of all lichen species are antibiotics and some lichen extracts kill the bacteria that cause boils, scarlet fever and pneumonia. I wonder now about the possible properties of the various lichen species on the rocks in my garden.

For any readers interested in the many ways that natural systems benefit our lives, this book is absolutely fascinating: Wild Solutions by Andrew Beattie and Paul R Ehrlich, published by Melbourne University Press
2001. Perhaps your library has a copy.