Look Out For Lichens

And learn what they can tell you about your environment

Have you ever stopped to look at a lichen? Up until a few years ago I probably never had, and I wasn’t even sure how to pronounce the word (most people say “ly-ken” nowadays, though some people still say lichen with a “ch” sound). In his book, The Walker’s Guide to Outdoor Clues and Signs, Tristan Gooley describes them as “the most underrated organisms you are likely to find on your walks,” but when you do take the time to notice them, you’ll see that lichens really are little works of art.

Despite the fact I now notice them all over the place, I wasn’t actually entirely sure what lichens were up until recently. It turns out they are a beautiful example of symbiosis - not a single organism, but rather a partnership between a fungus and an algae and/or cyanobacteria (I’ll be honest, I’m still unsure what cyanobacteria actually is even after Googling… need I remind you I’m an enthusiast, not an expert). Basically, each lichen is a tiny ecosystem of its own.

Lichen (and some moss) growing on my south-facing roof. I think this is Common Sunburst Lichen, or Xanthoria parietina, one of the most widespread species - all thanks to bird poo!

You’ll be able to spot lichen year-round, even in the frosty weather we are experiencing right now in the UK, as they are incredibly hardy things that can “survive at temperatures a hundred degrees lower than most plants,” according to Gooley. Not only that, but you can find them all over the place - on trees, walls, your roof, the pavement… Old churches and graveyards are especially good places to look.

A lichen (and moss)-rich forest in Dalavich, Argyll and Bute, Scotland. The air definitely felt clean here!

Lichens are good indicators - if you know your stuff, you should be able to learn many things about your area, including levels of sunlight, moisture, minerals and pollution,  just by identifying the species of lichen present. There are over 1,800 species in the UK, which fall into three main types. Getting to know these three types - fruticose, foliose and crustose - can help you figure out how clean the air is where you live. 

A type of fruticose/beard lichen on some flaky, foliose lichen-covered branches on one of the trees in Dalavich Forest, Scotland (where the air certainly felt clean!)

If you find lots of bushy lichen hanging from trees (known as fruticose lichen) near where you live, such as those floofy beard lichens in my photo above, lucky you: your area has really clean air and you can breathe easy! If you spot lots of flaky, leaf-like lichen (foliose), such as the coral-like lichen on the branch in the photo above, your area isn’t too badly polluted, and if you find only crust-like, flatter lichen (crustose) like lecanora muralis (which you might mistake for chewing gum or paint splatters), your local area has higher levels of pollution. I’m confident that, even if you live in a highly polluted city, you’ll be able to find at least one type of lichen if you look closely… give it a go!

Lichen Facts

• Lichens come in many colours, and some are dazzling! The brighter a lichen appears, the more likely it is to be exposed to plenty of direct sunlight. So if you spot a bright yellow lichen, like the lichen on my roof, it’s likely to be on a south-facing surface. Because of their unique characteristics, different species of lichens can serve as helpful navigation tools (if, like Tristan Gooley, you know what you’re doing!).

• Lichens can be used to make natural dyes, and some iconic Harris Tweed shades were originally created using lichens. If you do want to try making your own dyes from lichens, never pick lichens off a tree, only use lichens you find on the ground (a good time to forage for them is just after a storm).

• Certain species of lichens have been used in antibiotics and to treat cancer. They have also been used in the production of preservatives, embalming agents, poisons, perfumes, clothing fibres, cosmetics, food and more.

• Certain types of lichens can be used to gauge timescales. For example, if you spot a gravestone with a vast lichen blob on it, it’s likely to have been there a very long time. This is because crustose lichens are very slow growing. According to Tristan Gooley, “if you find a great circular patch of map lichen that has a 40cm radius, you are looking at something that has lain undisturbed for at least 400 years”.

• The word ‘lichen’ is derived from a Greek word, meaning eruption or wart. Lovely!

Sources and Further Reading

• The Walker’s Guide to Outdoor Clues and Signs by Tristan Gooley (book)

• Everything You Wanted to Know About Lichen (YouTube video by The Bald Explorer)

• What is a Lichen? Seven Types of Lichen Found on Trees (Woodland Trust article by Kylie Harrison Mellor )

• Nature and pollution: what lichens tell us about toxic air (Natural History Museum article by Beth Askham)

• Lichens and Pollution (YouTube video by Charles Joynson)

• How to Make a Natural Dye Using Lichens (YouTube video by Myra Made Color)

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