‘Why don’t you write a post about lichen?’ the SF asked recently, inspired by the plentiful specimens adorning the walls of our barn. What I knew about lichen would go on the proverbial postage stamp – not that this usually prevents me from writing about something, but since people devote their lives to studying the things I might be at a certain disadvantage. However, the more I thought about it, the more I realised that lichen is a distinctive – if unobtrusive – feature of life in rural SW France.
What is lichen? Before I did some research, I had no idea that it is not a single organism but a structure composed of two organisms – a fungus and an alga. They cohabit in a symbiotic relationship. In most cases, each can exist without the other in nature but in a few cases the fungus has become entirely dependent on the alga for its survival. The fungus needs carbon as its food source, which the alga provides via photosynthesis.
A great diversity of lichens exists. Some occupy a wide range of habitats while others need very specific and limited conditions in order to survive. Of course, there is much more to it than this and I’m not going to try to delve into it much further. But I found the British Lichen Society’s website very helpful in expanding my minimal knowledge.
Pollution indicator
What’s so important about lichens? They are a very sensitive indicator of air pollution and a possible means of gauging climate change. In heavily industrialised areas with coal-burning industry and power stations, very few lichens were able to exist and only one species thrived. Equally, and probably more important these days, agriculture and exhaust fumes produce nitrogen oxides that are toxic to some lichen species.
So when I say that lichen is a distinctive feature down here, it’s because it shows we enjoy low levels of certain types of air pollution. In fact, it colonises just about anything that is left outside long enough: walls, trees, shrubs, some aluminium garden chairs we brought from England and even the rubber trim on our 16 year-old car.
Natural embellishment
More than anything, though, it is strikingly beautiful when it glows in the sunlight on an old stone wall. The colours range from the usual green, through yellow, orange red and even white. I understand that these colour changes occur because of substances breaking down within the composite organisms.
Whatever the chemical reason, I find they embellish the ancient stonework in a way that enhances its natural beauty. Unfortunately, I also read that the waste from lichen eats into the stone, but it might take 900 years or more to do it (there’s some controversy about how long they can live), since it is very slow growing and long lived. I’ll just continue to enjoy it, then.
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Life on La Lune 
One of my favourite things about lichen is what lives within it – it contains a micro fauna called Tardigrades, otherwise known as water bears.
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Thank you for this fascinating information. I was previously unaware of these creatures, but I have looked them up and it appears they are among the most versatile and resilient on the planet. Their slow, rolling gait is the origin of the nickname, apparently. I would love to see one, but they are probably too small to be seen with the naked eye.
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Yes, they are beautiful and we have lots round here too. An artist friend of ours has produced a series of photographs of lichen in all their rainbow colours.
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How lovely! I’d love to see your friend’s photos. Lichen certainly lends itself well to photography.
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We went on a 7km walk today to seek out some Visigoth graves near Villarzel. I don’t think I’d ever taken any notice of lichen before….but having read your blog, I was fascinated by the incredible patterns and types that we saw on the walk. Your blog really enhanced our walk today…thank you !
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The Visigoth graves sound fascinating. I hope you’ll write about them on your blog: just the sort of thing I like. I’m pleased to hear that my musings on lichen enhanced your walk. It’s not the first subject that springs to mind for a blog post but once you start to learn about lichen you look out for it and notice its diversity far more.
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Our cars both have lichen on them too! I don’t think I’ve ever seen white lichen like yours before.
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It looks more like a splodge of paint, I admit, but it is indeed lichen.
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Wow, Vanessa, the photos are superb works of art! You clearly live in a very unpolluted environment…not that you needed the lichens to tell you…but they are oh so pretty.
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Lichens are wonderfully photogenic up close. They really are very pretty and I’m astounded at the range of colours they can achieve.
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This is fascinating, Vanessa! I see this beautiful lichen everywhere around here….now I know the rest of its story.
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I was surprised to find how complex an organism (or two, in fact) lichen is. Of course, the local stone is a wonderful foil for the more colourful varieties.
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Lichen is so beautiful and is an indicator of clean air, as you point out. I love the way it comes in all different colours, forms and shapes. We don’t get much of it in Amsterdam! Probably because we live near the motorway and despite the 60 miles per hour speed limit the air is still pretty polluted…
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I suppose it’s less likely to grow in or near big cities, although there are some species, apparently, that don’t mind air pollution caused by traffic. I had never really thought about it until we moved here, where it is everywhere. As I said in the post, leave anything outside long enough and it will colonise it!
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